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STC Twenty One Limited

DOA Procedures ST21/DOA/HB2

Part 2 – DOA Procedures

(UK CAA Part 21 Subpart J) The Waldorf Centre 1290 London Road Alvaston Derby DE24 8QP Tel 01332 576830 Fax 01332 576831

Document Reference: ST21/DOA/HB2

CAA Approval Reference: UK.21J.0198

STC Twenty One Limited Design Organisation Handbook 2 (DOA Procedures)

Section: 0 Revision: 31

Date: 06/08/2021

Page: i

© STC Twenty One Limited own the copyright of this document which is supplied on the express condition that it is not reproduced or used for any purpose other than that for which it is supplied and it is not communicated to any other person without the prior

permission of STC Twenty One Limited

Contents Part 2 – DOA Procedures

Contents

Amendment Record

List of Abbreviations

Distribution List

SECTION 1 – GENERAL

1.0 Introduction

1.1 Amendment Procedure

SECTION 2 - PROCEDURES

2.0 Report Completion

2.1 Establishment of the Type-Certification Basis of Changed Aeronautical Products

2.2 Audit of Design Organisation Procedure

2.3 Audit Remedial Action Procedures

2.4 Audit Personnel

2.5 Checker & CVE Selection Procedure

2.6 Certifying Staff Records Procedures

2.7 Occurrence Investigation and Reporting

2.8 Contractor & Sub-Contractor Selection Procedure

2.9 Liaison between STC Twenty One Ltd and the Selected Contractor & Sub-Contractor

2.10 Change or Repair Classification Procedure Part 21

2.11 Civil Change/Repair Record Procedure

2.12 Certification Programme, Establishment of Certification Basis and Compliance Checklist Procedure

2.13 Reserved

2.14 Reserved



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2.15 Minor Change/Repair Approval Procedure

2.16 Master Document List

2.17 Major Change/Repair Approval Procedure

2.18 Document Issue Procedure

2.19 Approved Document Filing Procedure

2.20 Design Report (DES) Procedure

2.21 Test Plan Procedure

2.22 Test Report Procedure

2.23 Service Bulletin Procedure

2.24 Equipment Qualification Procedure

2.25 Transfer of Airworthiness Responsibilities

2.26 Technical Report Procedure

2.27 Reserved

2.28 Design Office Instruction Procedure

2.29 Flight Manual Supplement Procedure

2.30 Electrical Load Analysis Report Procedure

2.31 Concession Procedure

2.32 Design Query Note Procedure

2.33 Hazard, Safety, Maintenance Analysis and Continued Airworthiness Procedure

2.34 Accomplishment Instruction Procedure

2.35 Reserved

2.36 Reserved

2.37 Company Design Procedures

2.38 Drawing Compilation Procedure

2.39 Drawing Issue Procedure

2.40 Drawing Filing and Retention Procedure

2.41 Reserved



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2.42 Reserved

2.43 Operational Suitability Data (OSD) Supplement Procedure

2.44 Airworthiness Monitoring Procedure

2.45 Repairs

2.46 Statement of Approved Design Data Procedure

2.47 Supplement Manual Procedure

2.48 Electrical Wiring Interconnection Systems (EWIS) Procedure

2.49 Instructions for Continued Airworthiness

2.50 Permit to Fly & Flight Conditions Approval

2.51 Environmental Protection

2.52 Wireless LAN Classification Procedure

2.53 Approved Model List (AML) Design Changes

SECTION 3 – APPENDICES

Appendix 1 - Master Form List

Appendix 2 - Approved Signatory Matrix

Appendix 3 - EXAMPLE DESIGN REPORT FOR THE SUBSTANTIATION OF FLIGHT CONDITIONS APPROVAL NOT RELATED TO FLIGHT TEST



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Amendment Record All amendments are to be recorded. Upon receipt of revisions, replace the revised pages in the Handbook and enter, in the table below, the Revision Number, Revision Date, Reason for Revision.

Revision No

Revision Date Reason for Revision

0 27/06/2011 Reverted to Revision 0 to remove Issue status of document by request of EASA

1 18/06/2012 Minor amendments to references and Procedure 2.9 re-written

2 04/10/2012 Amendments to clear audit findings, Revise procedures 2.3, 2.8, 2.9, 2.10, 2.13, 2.15, 2.21, 2.40, 2.41.

3 23/10/2012 Amendment to procedure 2.34 to reflect changes made to Accomplishment Instruction Form

4 18/04/2013 To remove the company forms from the handbook. To clear audit findings

5 16/07/2013

In support of DOA Significant Change approval:- Procedure 2.36 completely revised

New procedure 2.50 added Appendix 2 CVE signatory matrix amended to add limitations to A.

Kokkalis and D. Griffith Appendix 2 – Icing added to aerodynamics section

Appendix 3 amended in line with procedures 2.36 and 2.50 New form references added

Abbreviations amended

6 21/01/2014

Procedure 2.50.7 amended Appendix 2 CVE signatory matrix – AK added to

performance/Handling 2.5.17 amendment block reference changed

7 30/05/2014 Update of Management Personnel and update after general review of procedures

8 01/12/2014

Addition of procedure 2.0, all other procedures reviewed for inclusion of 2.0. Addition of 2.27, re-write of 2.21 and 2.22.

Update to 2.2, 2.3 and 2.24. Update of Part 21 references. Update to Appendix 2 CVE matrix.



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Revision No


9 13/03/15

Following an EASA audit the following have been updated: 2.1 Certification Basis, 2.10 Classification flowchart, 2.14 Compliance

Checklist, 2.19 Reference to DP added, 2.24 Software 2.27 software procedure, 2.46 SADD Procedure. Also 2.29 – FMS updated

10 05/05/15

2.0 addition of appendix 2-2 reference, 2.11 Addition of DP104 reference and removal of ‘deleted’ paragraphs, 218 minor typo changes, 2.24 EAF major changes, 2.26, 2.30, 2.32, 2.38 minor

typographical changes, 2.43 – MMEL major changes, 2.50 changes to 2.50.7 and PtF sign off, Appendix 2 changes.

11 18/12/15

2.7 update for regulation change. 2.9 updated to require a SADD is issued for all manufacture/installation drawings. Paragraph 2.15.4 reworded. 2.30 typographical correction. 2.31 & 2.32 updated post

EASA audit. 2.38.6 added. 2.34.3 preliminary removed. 2.36 – Deleted and moved to FTOM. 2.39 amended to remove preliminary.

2.46 amended to clarify the process and new 2.46.8 added.

12 10/03/16

2.7 further updated due to regulation change. 2.10 updated due to change in form, from experience. 2.12, para 2.12.6 added to clarify

procedure. 2.13 updated to reflect Compliance Record and documents produced. 2.19 updated to reflect office practice.

13 01/04/16

2.1 scope clarified to include minor 2.5 paragraph numbering added fully and 2.5.5 item 6 re-worded to match CVE cards. 2.7 updated to answer internal audit finding. 2.33

paras e. & f moved to 2.7.7 & 2.7.8. 2.28, 2.31 & 2.32 updated to answer internal audit finding. 2.50 paragraph numbering updated,

acronyms used consistently and reference to HoOoA deputies deleted. Addition of procedure 2.51.

14 12/07/16

OSD requirements added to 2.10, 2.12 & 2.13, 2.26. 2.16 – MDL procedure updated. 2.43 changed from MMEL to OSD supplement.

2.18 updated to answer internal audit finding. Appendix 2 updated to add new CVE.

15 31/01/17 The following procedures updated to address internal audits: 2.1,

2.13, 2.15, 2.16, 2.18, 2.19, 2.33, 2.39, 2.43, 2.47, 2.49, Appendix 2. Procedure 2.7 & 2.33 updated to better reflect the actual process.

16 02/05/17 Procedure 2.4, 2.7, 2.32 updated following EASA audit

17 18/05/17

The following procedures updated following EASA and internal audit findings; 2.0, 2.7, 2.22, 2.25 (DDP) deleted. Procedure 2.5, 2.6, 2.34 updated to allow for Design Signatories to be separate from CVEs. 2.29 removed ref to form. 2.33 updated post S21.OCC-0011. 2.38 updated for drawing sign off on database. Appendix 2 updated to

add CVE LB and OSD.

18 13/07/17

2.8 Definitions amended. 2.35 transmittal letter procedure updated, ref 2.47 changes.

2.47 Supplement Manual – major update. 2.21 reference to DP110 added.

19 22/08/17 2.8, 2.9, 2.12, 2.23, 2.25 (introduced) Appendix 1 - Forms



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Revision No


20 13/12/17

Distribution list updated and Part 21 references updated in various procedures. Procedure 2.0, 2.2, 2.8, 2.9, 2.10, 2.34, 2.45, 2.46, 2.50

and appendix 1, 2 & 3 updated. Introduction of EASA approved procedure 2.52.

21 02/08/18

Distribution list updated, procedure 2.5 (linked to S21.OCC-0016), 2.8, 2.24 (all change), 2.33, 2.38, 2.39, 2.46 SADD procedure to add a reference number, 2.50 flow chart updated. Appendix 2 addition of

CVE & Design Signatory. Addition of 2.53 AMLs. 2.27 & 2.52 definition of DAL changed. 2.34 sign off change

22 18/10/18 2.0, 2.1, 2.9, 2.18, 2.38, 2.39 amended following audit findings. 2.24

updated. Appendix 2 CVE added, TM. Comlux & TM added to distribution list.

23 25/01/19 The following were updated following a major review (mostly linked to internal NCs) Procedure 2.2, 2.3, 2.4, 2.7, 2.10, 2.12, 2.17, 2.25,

2.31, 2.32, 2.33, 2.41 (deleted), 2.47, 2.50, 2.52, 2.53 & appendix 3.

24 08/10/19

Major Repair Approval – 2.45 completely rewritten (was Evaluation of Un-repaired Damage Procedure); “change/repair” wording

updated accordingly in 2.10, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.46 and Appendix 1.

2.48 EWIS rewritten. Appendix 2 CVE added, Distribution List updated accordingly.

2.29, 2.47 revised ref EASA NC0069. Due to internal audits: 2.27 deleted (covered in 2.24 as amended);

2.35 deleted; 2.21, 2.22, 2.25, 2.30, 2.34 revised.

25 14/01/20 Revision 25 was sent to EASA for review but required changes prior to release for use. The changed areas are the same as those for revision 26.

26 04/03/20

Procedure 2.0 updated following internal audit. 2.1 deleted. Appropriate content added to 2.12 and the associated form. 2.12 revised for compliance to Commission Regulation 2019/897. 2.13 deleted. Appropriate content added to 2.12 and 2.16 and the associated forms. 2.14 deleted. Appropriate content added to 2.12 and the associated form. 2.15.4 and 2.15.5 amended. 2.15.10 deleted and content moved to 2.45. 2.13 removed from references in 2.15. 2.16.3 amended to remove reference to the COMP and CCL. New 2.16.4 inserted to reflect the approval statement. Original 2.16.4 and 2.16.5 renumbered due to the above. New 2.17.2 inserted for Major Change application. Original 2.17.2 through 2.17.13 renumbered due to the above. 2.17.5 amended to reflect HoOoA rather than HoD. 2.17.6 ‘EASA’ replaced with ‘Agency’. 2.17.7 amended to refer to Type Certification basis and add OSD Certification Basis. 2.17.8 references to 2.13 replaced with 2.16. “No unsafe Features” statement added. 2.17.9. Procedure references updated. 2.17.11 ‘EASA’ replaced with ‘Agency’. 2.17.12 ‘EASA’ replaced with ‘Agency’. various updates introduced.



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Revision No


2.13 removed from references in 2.17. 2.21.5(a) unnecessary wording removed, and the note amended to add “where applicable”. 2.21.5(b) reference to 2.21.7 removed. 2.21.6(c)(d)(e) wording added. 2.21.6(f) added to comply with Commission Regulation 2019/897. 2.23.7 approval statement added per Commission Regulation 2019/897. 2.28.5 approval statement amended per Commission Regulation 2019/897. 2.29 definitions amended to reflect updated requirement (GM 21.A.91). 2.29 various amendments made throughout the procedure. Approval methods amended per current Agency standards. 2.33 reference to Compliance Record removed from 2.33.8 and 2.33.9 and replaced with 2.18. 2.43.8 reference to 2.1 replaced with 2.12. 2.45 amended per Commission Regulation 2019/897. 2.13 and 2.14 removed from references in 2.45. 2.12 added to references. 2.46.4 wording revised for clarity. 2.46.6 deleted. 2.13 removed from references in 2.46. 2.47.25, examples added for clarity. 2.50.1 paragraph 8 added per Commission Regulation 2019/897. 2.52.11 additional wording added for clarity. Appendix 1 form S21.2.12.REP.005 renumbered and renamed. Appendix 1 forms S21.2.13.REP.006 and S21.2.14.REP.007 deleted. Appendix 2 Approval Signatories updated to reflect obligation 21.A.265(h) per Commission Regulation 2019/897 and add clarification of document types. Appendix 2 removal of ‘Documents Requiring CVE Approval Signatories’. Appendix 2 Accomplishment Instruction approval altered for all Changes.

27 13/05/20

2.12, additional form reference added. 2.43, MMEL section re-written. 2.7.9 & 2.7.10 Amended Appendix 1 Master forms updated to reorder and add: S21.2.12.REP.005-MAJ S21.2.12.REP.005 – Major Matrix S21.2.12.REP.006-MIN S21.2.12.REP.006 – Minor Matrix

28 26/10/20

1. Distribution List corrected. 2. 1.0 Introduction: Note added concerning references. 3. References throughout: aligned to HDBK3 revision 27 plus

various Part 21 reference corrections made. 4. 1.1 Amendment Procedure aligned to Handbook 1; 1.1.3

Amended to ensure form changes match procedures.



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Revision No


5. Multiple sections amended throughout document to add deputies in reference to HOD & HoOoA duties.

6. 2.5.10 CVE selection criteria revised. 7. 2.9.16 added for document location. 8. 2.10.4 revised to clarify when classification justifications are

required. 9. 2.11 revised. 10. 2.16.4 Removed definition of signature location. 11. 2.21.6 Test witnessing clarified. 12. 2.24 Note added reference firmware. 13. 2.24 Equipment performance test data acceptance updated. 14. 2.25 Transfer of Airworthiness Responsibilities updated. 15. 2.32.8 DQN issue clarified. 16. 20.50.20 (1) Deleted

• Amended to include instruction for documentation location • Amended to remove redundant aspects and references.

17. 2.52 Procedure Limitation revised. 18. Appendix 2 Approval matrix & Signatory approval/limitations. A

Harper removed. 19. Appendix 3 re-written.

29

1. Appendix 2: Signatory Approval Matrix: CS27 & CS29 checked, and crosses added against non-relevant sections for DW. Handling added to title of Performance (etc) and HMI added to list of areas.

2. References to Box.com has been removed from procedures 2.25.10, 2.25.15 and 2.25.23.

3. Procedure 2.1 re-instated (from ST21/DOA/HB2 Rev 24) with amendments for current Part 21.

4. 2.17.2 re-formatted; 2.17.7 paragraph references corrected; 2.17.8 clarified;2.17.12 revised.

5. Note from procedure 1.0 removed and relocated onto forms S21.REP.005-MIN and S21.REP-006-MAJ.

6. Part 21 references revised. 7. Paragraph 2.10.3 & 2.45.4 revised, to address change to

Classification Section of Repair Form.

30 22/04/2021

1. Changes associated with DOA authorisation transfer from EASA to UK CAA.

2. Clarification added to 2.50 in relation to the above. 3. Note (removed at Rev 29) reinstated to 1.0 4. Clarification added to 2.1. 5. Procedure 2.26 removal of HOD signature from the

technical report.



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Revision No


6. Procedure 2.24 Software/CEH DAL wording changed tospecifically refer to avionic equipment only.

7. Procedure 2.5.27 updated.8. Appendix 2 updated Limitation correction to CVE for DG.

31 06/08/21

1. Amendment instruction updated from insert to replacerevised pages, insertion date and inserted by columnremoved.

2. Procedure 2.2 updated following S21.QAR-03043. 2.12.2 excel matrix now a tool and not mandatory.4. Procedures 2.13, 2.14, 2.27, 2.35, 2.36 & 2.41 re-identified

from Deleted to Reserved.5. Deleted paragraphs throughout either fully removed or

shown as reserved if mid sequence.6. 2.5 – Selection procedure updated.7. 2.19.1, 2.19.4 & 2.19.5 updated to refer to cloud-based

service for electronic back up of data. 8. 2.19.6 deleted – requirement for hard copy.9. 2.24 Equipment Qualification Updated.10. Procedure 2.42 deleted. Duplicate of HDBK 1 procedure.11. 2.47.9 Reference to hard copy removed12. HOA changed to HoOoA throughout document.13. EMI form removed from appendix 114. Appendix 2 – updated to align with CAA Panels. Limitation

included. Derek Harper, Alex James and Matthew Hubbard added.



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List of Abbreviations UAbbreviationU UMeaning AED Aero Engineering Design Ltd AFM Airplane Flight Manual AMC Acceptable Means of Compliance AML Approved Model List ATA Air Transport Association of America BAe British Aerospace BCAR British Civil Airworthiness Requirements CAA Civil Aviation Authority CAD Computer Aided design CAP Civil Airworthiness Publication CCD Cabin Crew Data CCR Civil Change Record CDI Compliance Demonstration Item CS Certification Specification CVE Compliance Verification Engineer DAL Development Assurance Level DDP Declaration of Design and Performance DOA Design Organisation Approval /Approved Design Organisation DOH Design Organisation Handbook DOI Design Office Instruction DQN Design Query Note EA Equipment Assessment EAF Equipment Assessment Form EASA European Union Aviation Safety Agency ELA Electrical Load Analysis EMC Electro-Magnetic Compatibility EMI Electro-Magnetic Interference ETSO European Technical Standard Order FAA Federal Aviation Administration FC Flight Conditions FHA Fault Hazard Analysis FTOM Flight Test Operations Manual GM Guidance Material HIRF High Intensity Radiated Frequency HISM Head of Independent System Monitoring HoOoA Head of Office of Airworthiness HoD Head of Design IAW In accordance with JAA Joint Aviation Authority LAN Local Area Network Ltd Limited MCSD Maintenance Certifying Staff Data MDL Master Document List



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Abbreviation Meaning MEL Minimum Equipment List MMEL Master Minimum Equipment List MOA Maintenance Organisation Approval/Approved Maintenance Organisation MOC Method of Compliance MPD Maintenance Planning Document NAA National Aviation Authority nr. Number OoA Office of Airworthiness OPR Open Problem Report OSD Operational Suitability Data POA Production Organisation Approval/Approved Production Organisation PtF Permit to Fly RF Radio Frequency SB Service Bulletin SSA System Safety Assessment STC Supplemental Type Certificate STC21 STC Twenty One Limited WLAN Wireless Local Area Network



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Distribution List The following are nominated holders of “controlled” copies of the Design Organisation Handbook.

DOH Copy Number Nominated Holder Location

1 Master Hard Copy STC Twenty One Ltd, Derby, UK

2 The Authority CAA Aviation House, Sussex, England

3 Master Electronic Copy* Cloud Server

* This server is managed by STC Twenty One Limited. An electronic copy of this procedure’s manual is available to authorised personnel.



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SECTION 1 – GENERAL



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1.0 Introduction This Handbook contains the procedures to be followed in order to demonstrate compliance with CAA UK Part 21 Subpart J, Design Organisation Approval. All references to Part 21 in this Handbook are to UK Part 21. Important Note: The References Section at the end of each procedure is intended to provide further reading references to the reader. Specific Compliance to Part 21 is documented in the DOA Compliance Checklist.



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1.1 Amendment Procedure 1.1.1 Amendments to this Procedures Handbook shall follow section 1.3 of Handbook 1. 1.1.2 Reserved.

1.1.3 It is the responsibility of the Head of Design to ensure proposed procedural

changes match proposed changes to forms.

References: Part 21.A.243(c)



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SECTION 2 - PROCEDURES (MANAGEMENT OF CHANGES & REPAIRS TO TYPE DESIGN)


Section: 2.0 Revision: 31

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2.0 Report Completion Purpose: To provide guidance to the completion of reports produced by STC Twenty One

Ltd. Scope: From front page layout and standard formatting to the signing and approval of

documents. Definitions: Wet-ink: an ink-signature. Digitally signed: either electronic pen signature, or embedded image. Procedure: 2.0.1 All new forms should be compiled on the latest available templates located in the

Templates folder. Up-issues of forms will be reviewed on a case by case basis to determine if there is a need to add them to the latest template.

2.0.2 All reports require a serial number that will be the next sequential number taken

from the database. NOTE: If a new report has been created within the database, ensure that there is a

corresponding procedure within this handbook, or a temporary revision is sought to this handbook.

2.0.3 The front sheets will bear the company name and address. 2.0.4 Reports will be controlled by an issue number. The first official issue of each report

is Issue 1. Prior to the first official release documents will be given a prototype issue number, represented as P1, P2 etc. Where documents are required by the Authority in support of drafting the TV/STC, the document (e.g. MDL, FMS) may be supplied at issue 1 without reference to an approval. The document may not be issued to a customer without the approval information being completed.

2.0.5 Reports will require a descriptive title. 2.0.6 Where documents are used for the showing of compliance the front page of the

report will be signed by the compiler and checker and the relevant CVE will sign for the applicable category.

2.0.7 Where the document is not used for the showing of compliance, the front page of

the report will be signed by the compiler, and relevant checker and approver.



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2.0.8 Any amendments to the document will be identified by raising the issue of the

document to the next numeric issue, which usually starts on sheet 2 of the document.

2.0.9 All reports will have an amendment record detailing issue, date, and the reason

for the amendment. The record shall contain all amendments at all issues.

2.0.10 All signed and approved original signature sheets (‘wet ink’ or ‘digitally signed’) will be filed in accordance with procedure 2.19. Where a form is digitally signed the signatory must ensure that the digital signature is not editable.

2.0.11 Checker or Approvers/CVE can only sign a report providing that they had no part

in the compilation.

2.0.12 Document Approval will be used in documents that do not demonstrate compliance but will ensure a non-compliance will not be introduced.

2.0.13 Compliance Verification will be used in place of Document Approval where compliance is demonstrated.

2.0.14 It is possible for the same Approver / CVE to also sign for Checking.

Typical Sign-Off Sheet

Initial Issue:

Compiled By: Date:

Signature:

Signed By: Signature:

Category(s)

Document Check Compliance Verification

Categories Key

1 Flight and Human Factors 2 OSD-FC 3 Structures 4 Hydromechanical Systems 5 Electrical Systems

6 Avionic Systems 7 Powerplant Installation and Fuel Systems 8 Environmental Control

Systems (ECS) 9 Noise, Fuel Venting and Emissions 10 Software, Airborne Electronic

Hardware (AEH), Development Assurance (DA)

11 Cabin Safety 12 Safety Assessment (SA) 13 Transmission 14 ICA 15 OSD-MMEL

16 OSD-SIM 17 OSD-CC 18 OSD-MCS 19 Propulsion



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2.0.15 Documents will be issued in accordance with 2.18. 2.0.16 Documents will be filed in accordance with 2.19. 2.0.17 Where the statement ‘The technical content of this document is approved under

the authority of the DOA ref. UK.21J.0198’ is used, this will be signed by the Head of the Design Organisation. See also Appendix 2.

References: 2.18 Document Issue Procedure

2.19 Approved Document Filing Procedure Part 21.A.239(b), 21.A.265(h)



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2.1 Establishment of the Type-Certification Basis of Changed Aeronautical Products

Purpose: To provide guidance for establishing the type-certification basis for changed

aeronautical products using the changed product rule in Part 21.A.101. Scope: From the identification of a change to establishing and recommending the type

certification basis. Definitions: Adequate type-certification basis - The type-certification basis for a changed

product under 21.A.101 is considered adequate when the Authority determines that it provides adequate standards for the design change, i.e. when the certification specifications of the applicable airworthiness code and prescribed special conditions provide an appropriate level of safety for the changed product and do not result in any unsafe design features.

Earlier certification specifications - The certification specifications of the

applicable airworthiness code in effect prior to the date of application for the change, but not prior to the existing type-certification basis.

Existing type-certification basis - The certification specifications of the applicable

airworthiness code, special conditions and equivalent level of safety findings incorporated by reference in the type-certificate of the product to be changed.

Non-significant change - Any product level change to the type-certificate that does

not meet the criteria for either a significant or substantial change. Latest certification specifications - The certification specifications of the applicable airworthiness code in effect on the date of application for the change. Previous relevant design changes - Previous design changes, the cumulative effect

of which could result in a product significantly or substantially different from the original product or model, when considered from the last time the latest certification specifications were applied.

Product level change - A change or combination of changes that makes the

product distinct from other models of the product (for example, range, payload, speed, design philosophy). Product level change is defined at the aircraft, engine, propeller, or APU level of change.

Significant change - A change to the type-certificate significant to the extent that it changes at the product level one or more of the following: general configuration, principles of construction, or the assumptions used for certification, but not to the



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extent to be considered a substantial change. The significance of the change must be considered in the context of all previous relevant design changes and all related revisions to the certification specifications of the applicable airworthiness code. Not all product level changes are significant.

Substantial change - A change which is so extensive that a substantially complete

investigation of compliance with the applicable type-certification basis is required, and consequently a new type certificate, in accordance with 21.A.19.

Type-certification basis - The certification specifications of the applicable airworthiness code, environmental protection and OSD requirements, as established in 21.A.101, as appropriate; special conditions; and equivalent level of safety findings applicable to the product to be certificated.

Procedure: 2.1.1. All changes/repairs are classified in accordance with procedure 2.10 and

procedure 2.45 respectively. All changes classified as minor are non-significant changes.

2.1.2. All changes classified as major may be further classified as substantial, significant

or non-significant changes. 2.1.3. A change identified as a substantial change requires a new type certificate. As STC

Twenty One Limited is not a Type Certificate Holder, this level of change is beyond the scope of approval and cannot be continued.

2.1.4. 21.A.433 requires a repair design to comply with the type-certification basis incorporated by reference in the type-certificate, or supplemental type-certificate.

2.1.5. 21.A.95 requires a minor change to a type-certificate to comply with the type-certification basis, operational suitability data certification basis and the environmental protection requirements incorporated by reference in the type-certificate.

2.1.6. 21.A.101(a) requires a major change to a type-certificate to comply with the latest Certification Specifications (for airworthiness and OSD), unless the change meets the criteria for the exceptions identified in 21.A.101(b) or (c).

2.1.7. If the certification specifications applicable on the date of the application for the major change do not provide adequate standards with respect to the proposed change, the change and areas affected by the change shall also comply with any special conditions, and amendments to those special conditions, prescribed by the Authority in accordance with point 21.B.75, to provide a level of safety equivalent



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to that established by the certification specifications applicable on the date of the application for the change.

2.1.8. For non-significant major changes where compliance with the latest amendment

of the applicable certification specifications will not contribute materially to the level of safety, would be impractical, or is in an area not affected by the change, the Head of Office of Airworthiness, or their nominated deputy, may accept compliance with earlier certification specifications, but not preceding the TC basis.

2.1.9. For significant changes where compliance with a later amendment of the

applicable certification standards will not contribute materially to the level of safety, would be impractical, or is in an area not affected by the change, STC Twenty One Limited will require individual agreement with the Authority.

2.1.10. STC Twenty One Limited may not use an Airworthiness Code amendment prior to

that specified in the Type Certificate. 2.1.11. By derogation from points 2.1.6, 2.1.8 or 2.1.9, the change and areas affected by

the change may comply with an alternative to a certification specification designated by the Authority if proposed by STC Twenty One Limited, provided that the Authority agrees that the alternative provides a level of safety which is:

(i) equivalent to that of the certification specifications defined under 2.1.4, 2.1.6 or 2.1.7 above; or (ii) compliant with the essential requirements of Annex II to Regulation (EU) 2018/1139.

2.1.12. If STC Twenty One Limited choose to comply with a certification specification of an

amendment to the airworthiness code that is effective after the filing of the application for a change to a type, they shall also comply with any other certification specification that the Authority finds is directly related.

2.1.13. When establishing the type-certification basis for the changed product for

recommendation to the Authority or Head of Office of Airworthiness acceptance, the flow chart on the following page and AMC & GM for Part 21 is to be used.

2.1.14. The operational suitability data certification basis is established in the same way

as defined above. 2.1.15. The applicable environmental requirements are those defined in the TCDS, as per

21.A.101(a). 2.1.16. The agreement of the type-certification basis is formally agreed through the

Certification Programme. (See Procedure 2.12).



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Developing a Proposed Certification Basis for a Changed Product Pursuant to point 21.A.101

References: Part 21.A.19, 21.A.95(b), 21.A.101(c)(f)(g).



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2.2 Audit of Design Organisation Procedure Purpose: To define the procedure for the internal auditing of STC Twenty One Ltd Design

Department. Scope: Audits carried out by STC Twenty One Ltd Definitions: Scheduled Audit: Audits carried out in accordance with STC Twenty One Ltd

audit plan. AD-HOC Audit: An audit, or non-conformity raised, outside of the scheduled

audit plan. Categorisation of Non-Conformities:

Level 1: Non-Compliance with a requirement which could lead to

uncontrolled non-compliances with applicable design data and which could affect the safety of the aircraft.

Level 2: Any non-compliance, including non-compliance with own procedures, not classified as Level 1.

Level 3: Potential problems that could lead to non-compliance. Procedure:

2.2.1 An audit plan will be created by the HISM and approved by the HoD. The audit plan is usually based on a 2 year audit cycle and covers those key procedures that are used, either directly or in-directly, to demonstrate compliance with Part 21 requirements.

2.2.2 All audits carried out; whether they are a scheduled, ad-hoc or sub-contractor on-

site audit, will be recorded in a report raised via the database. The database will allocate the next sequential number identified as either S21.QAR-xxxx, for internal audits, or S21.SUB-QAR-xxxx, for sub-contractor audits.

2.2.3 When raising an audit report in the database, the procedure to be audited will be

selected, therefore allocating a report to a specific procedure. Any non-conformities raised will also be linked to this report.

2.2.4 If during the completion of an audit a non-conformity is discovered, a non-

conformity will be raised in the database via the ‘add non-conformity’ button. The non-conformity will be identified as either S21.NC-xxxx-xx for internal audits or S21.SUB-NC-xxxx-xx for sub-contractor audits.



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2.2.5 Where a non-conformity has been raised, an appropriate level will be selected by the auditor, as per the definitions section of this procedure. Non-conformities will then be addressed as per procedure 2.3.

2.2.6 Once all non-conformities have been closed the audit report will be considered

closed by the database. For scheduled audits the next audit cycle can then be set. 2.2.7 An annual review of the internal audits and non-conformities raised will be carried

out by an appropriate person appointed by, and reporting to, the HoD. Where possible the person carrying out the review should not be the same person who compiled the audit report(s). The review can include, but is not limited to, information from previous reviews, audits carried out in the current audit cycle, sub-contractor audits, CAA audits, trends, and customer feedback.

2.2.8 The annual review will be reviewed by the HoD, HoOoA and HISM. They will

determine if actions are required to address any trends or issues identified. 2.2.9 Closed audit documentation shall be saved on the database and retained for a

minimum of 2 years. References: 2.3 Audit Remedial Action Procedure 2.4 Audit Personnel Procedure. 2.8 Contractor and Sub-Contractor Selection Procedure

Form S21.AUD.REP.033 Part 21.A.239(a)3



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2.3 Audit Remedial Action Procedures Purpose: To define the procedure for remedial action as a result of an audit. Scope: From the raising of an audit report to the satisfactory completion of the remedial

action. Definitions: Timescales for Remedial Action: Level 1: A Level 1 finding shall be actioned and closed within 21

working days. Level 2: A Level 2 finding shall be actioned and closed within 3

months. Level 3: A Level 3 finding shall be actioned and closed at the first

available opportunity but not later than 12 months. Procedure: 2.3.1 Audit personnel shall raise audit reports in accordance with procedure 2.2. Where a

non-conformity is raised it will be accepted by the HoD and the response will include the root cause, corrective action, and preventative action. This can be completed by someone allocated by the HoD and the final sign off will be by the HoD and then accepted by the HISM.

2.3.2 The non-conformity is to be answered within a specific timescale depending on the

level of non-conformity raised, as per the definitions section of this procedure. If more time is required to complete the non-conformity an extension can be requested. This is done in the database and reasons for the extension are required. The extension is to be agreed by the auditor.

2.3.3 Following agreement by the HoD that the root cause, corrective action and

preventative action have been completed, the auditor will ensure that the actions are suitable and close the non-conformity on the database.

2.3.4 The closed audit documentation shall be retained for a minimum of 2 years. References: 2.2 Audit of Design Organisation Procedure 2.4 Audit Personnel Procedure Form S21.AUD.REP.028 Form S21.AUD.REP.029 Form S21.AUD.REP.030

Part 21.A.239(a)3



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2.4 Audit Personnel Purpose: To ensure quality audit personnel are suitable to carry out internal audits of STC

Twenty One Ltd Design Department. Scope: The identification of suitable audit personnel. Definitions: None. Procedure: 2.4.1 Authorisation to auditors will be given based on work experience and/or completion

of training relating to a particular function, together with a demonstrated knowledge of company procedures and Part 21. The auditor may call on experts to assist with the audits as required.

2.4.2 Auditors carrying out internal or sub-contractor audits are responsible to the Head

of Independent System Monitoring (HISM). 2.4.3 2.4.2 The following personnel can carry out audits, including internal and sub-

contract, on behalf of STC Twenty One Ltd:

1. John Marchant 2. Peter Gaughan, when deputising for the HISM (ref: procedure 1.7.5)

2.4.4 The HoD is responsible for the selection of personnel who carry out the annual

reviews required by procedures 1.3.7 and 2.2.6. References: 2.3 Audit Remedial Action Procedure Part 21.A.239(a)3



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2.5 Checker & CVE Selection Procedure Purpose: To ensure personnel selected to be design signatories or Compliance Verification

Engineers (CVE) are suitable to carry out the functions under the Design Organisation Approval.

Scope: From the identification of a suitable Checker or CVE to their appointment by the

Head of Design (HoD) / Head of Office of Airworthiness (HOOOA) and the amendment of the Company Handbook.

Definitions: Checker – Responsible for the Technical Check of documents and drawings. For

detailed Checker definitions refer to Handbook 1

Approver – Responsible for the Approval of the content for non-compliance demonstrating documents and drawings. For detailed Approver definitions refer to Handbook 1

Compliance Verification Engineer – Responsible for the verification of the showing

of compliance. The CVE is also an approver. For CVE definitions refer to Handbook 1.

Procedure: Checker and CVE selection and qualifications 2.5.1 A Checker or CVE will be selected on a point based system and if required an

interview with the HoD/HOOOA.

2.5.2 The applicant will submit biographical information and evidence to support the application.

2.5.3 This information will be used by the HoD/HOOOA to formally accept/reject the applicant. Additionally, any limitations that are imposed on the applicant will be added to the application.

2.5.4 Applications are evaluated using a points-based system related to answers to a specific set of questions according to the role/function being performed. The evaluation is conducted by the HoD and/or HOOOA. Where insufficient information has been provided, the applicant will be advised via email and invited to provide additional information. If the applicant attains sufficient points, they are



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then sent an email requesting them to complete the application by indicating what discipline panel applies to their application.

2.5.5 Again, for each panel selected, the applicant is required to provide supporting information. For each panel requested, the HoD and/or HOOOA either accept or reject the panel requested by the applicant and record notes as required to justify the decision. If the panel is accepted, limitations will be recorded. As in the first part of the application, the applicant may be contacted to provide additional supporting evidence.

2.5.6 A Checker applicant will also be reviewed for competency to perform conformity inspections, compliance inspections and witness testing.

2.5.7 An interview will be performed with each acceptable applicant prior to initial approval.

2.5.8 Once satisfied, the HOOOA and HoD signify their approval within the Certifying Staff Record (Procedure 2.6) which is then digitally recorded.

2.5.9 Information documented will be used to generate the signatory matrix (Appendix 2).

2.5.10 Access to this information will be limited to the HoD/HOOOA/HISM and upon request UK CAA.

2.5.11 A Checker or CVE will be able to amend their records and update their details, as required.

2.5.12 To be considered for a Checker or CVE position the candidate should meet the

following criteria:-

a. Normally, three years for a Checker or five years for an Approver/CVE, relevant work experience of which at least two years should be from the aeronautical industry in an appropriate position relevant to the discipline;

b. Experience and expertise in the application of aviation safety standards and safe operating practices;

2.5.13 In addition to the above, for a CVE position the candidate should meet the

following criteria:-



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a. A CVE should hold an engineering degree or equivalent. i.e. HNC, Part 66 Engineering License relevant to the discipline;

b. For a CVE, have completed an Part 21 training course, held a CVE role in a previous employment or is able to demonstrate by other means e.g. interview, that they have a satisfactory knowledge of Part 21 and Certification Specifications

c. In the case where a CVE candidate has not met all of the criteria set out above, if it can be demonstrated through interview and recorded concentrated experience, that they are capable of holding a CVE approval (albeit with limitations), the HoOoA may, at their discretion, issue the CVE approval.

2.5.14 The individual for CVE applications, having a suitable background and experience, will be interviewed by the HoD and HOOOA. During the interview the candidate will be asked questions on:

a. Examples of past experience from the relevant field in which approval is

sought.

b. Current Air Legislation.

c. Company Procedures.

d. Part 21.

e. CS23, 25, 27, 29 etc. 2.5.15 In the case where a candidate has been actively involved in a DOA Significant

Change approval during which there has been direct involvement with Authority experts e.g. interview or meetings, an additional internal interview, at the discretion of the HOOOA, may be waived provided that the interview / meeting with the Authority covered the same topics as an internal interview. This should be recorded in the certifying staff record for the appointed CVE.

2.5.16 The HoD and the HOOOA will discuss the candidate’s suitability and, if acceptable,

will inform the candidate of their approval and limitations in writing. A copy of this will be held with the notes and résumé. In the case where the CVE appointment is related to a DOA significant change approval, the Authority may request a second interview with the candidate.

Checker and CVE authorisation 2.5.17 A Checker or CVE, when selected, is categorised against a discipline for which they

have been shown to demonstrate competence and expertise. The discipline categories are defined as follows:



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1. Flight and Human Factors 2. OSD-FC 3. Structures 4. Hydro Mechanical Systems 5. Electrical Systems 6. Avionic Systems 7. Powerplant Installation and Fuel Systems 8. Environmental Control Systems (ECS) 9. Noise and Fuel Venting 10. Software, Airborne Electronic Hardware (AEH), Development Assurance

(DA) 11. Cabin Safety 12. Safety Assessment (SA) 13. Transmission 14. ICA 15. OSD-MMEL 16. OSD-SIM 17. OSD-CC 18. OSD-MCS 19. Propulsion

2.5.18 The CVE’s scope of approval contains categories in order to further define

permitted aircraft categories for which they are approved to sign compliance documents. This is based on their previous experience. These categories are as follows:

a. CS-23 Normal, Utility, Aerobatic and Commuter Aeroplanes

b. CS-25 Large Aeroplanes

c. CS-27 Small Rotorcraft

d. CS-29 Large Rotorcraft 2.5.19 If required, limitations may be applied to specific areas of a Checker / CVE’s scope

of approval if it is considered that additional experience is required in a particular discipline, aircraft classification or aircraft system.

2.5.20 Typically, Checkers will not have limitations applied to specific items within panels

they have been approved for. It is considered that Checkers can still perform their roles and are expected to know their own limitations in terms of knowledge and act accordingly. This is acceptable as the final sign off/responsibility is with the Approver / CVE.



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2.5.21 The Checker / CVE will be notified of their approval discipline, categories and specific limitations in writing after the Checker / CVE interview.

2.5.22 Scope of Approval and Limitations are detailed in Appendix 2 to this handbook.

2.5.23 Approval and limitations are further documented on the design signatory / CVEs

Certifying Staff Record (See procedure 2.6). References: Handbook 1 – 1.10 Part 21.A.239(b), 21.A.243(d) HoOoA



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2.6 Certifying Staff Records Procedures Purpose: To ensure records for the personnel selected to be Compliance Verification

Engineers and/or Office of Airworthiness Staff are retained, updated and that access to them is suitably controlled.

Scope: From the creation of the staff record through its amendment to its filing. Definitions: None. Procedure: 2.6.1 Copies of all Certifying Staff Records are to be kept by the Office of Airworthiness

using Form S21.2.6.REP.000. Access to records is restricted to those viewing their own records, Office of Airworthiness staff and Senior Management only.

2.6.2 The records to be retained on file are:

a. Name b. Address c. Date of Birth d. Position Held within Organisation e. Qualifications f. Résumé of Experience g. Record of Training and Standard Attained h. Scope of Approval i. Notes from Approval Interview j. Date of First Issue of Approval (and expiry as applicable)

2.6.3 No individual is permitted to alter their records. Alterations can only be carried out

by the Office of Airworthiness. 2.6.4 The individual’s record will be kept for at least 2 years following the withdrawal of

his/her authorisation or cessation of his/her employment with the Company. 2.6.5 The records are to be updated following any relevant change to the individual’s

experience, training, or scope of approval. This is the responsibility of the Office of Airworthiness.

2.6.6 The records are to be made available in a timely manner to Certifying Staff wishing

to view their own records and to the Authority on request.



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References: 2.5 Checker & CVE Selection Procedure. Part 21.A.243(d)



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2.7 Occurrence Investigation and Reporting Purpose: To ensure failures, malfunctions, defects, and occurrences resulting from STC

Twenty One Ltd design changes or repairs are correctly investigated and reported. Scope: From the discovery of a reportable occurrence, through to its reporting to all

parties, and the satisfactory conclusion of the action. Definitions: Occurrence - Any safety related event which endangers or which, if not corrected

or addressed, could endanger an aircraft, its occupants or any other person and includes in particular an accident or serious incident (Regulation (EU) 376/2014).

Mandatorily Reportable Occurrence (MOR) – Occurrences which may represent a significant risk to aviation safety and which fall into defined categories listed in Article 4 of Regulation (EU) 376/2014.

Voluntarily Reportable Occurrence (VOR) – Any occurrence or safety related information by individuals which are not subject to mandatory reporting. Article 5 of Regulation (EU) 376/2014.

Procedure: 2.7.1 Maintenance Organisations, Production Organisations, Operators, and sub-

contractors are obligated to inform STC Twenty One Ltd immediately, of any occurrences that may be classified as an MOR, as defined in Regulation (EU) 2015/1018, specifically Annex II.

2.7.2 On notification of an occurrence or potential occurrence, an STC Twenty One

Limited Occurrence Assessment will be raised using form S21.2.33.REP.024. 2.7.3 It should be determined in the first instance, whether the occurrence is

determined as reportable. Reportable failures, malfunctions, defects or other occurrences will be notified in accordance with UK CAA publication CAP382. https://aviationreporting.eu/ shall also be used. Reports shall be made as soon as practicable but not later than 72 hours after the occurrence has been identified.

2.7.4 The above will be determined through the completion of Section A of the

Occurrence Assessment. This will be completed by the HoOoA (or deputies) and will consider the impact the occurrence has on airworthiness.

2.7.5 If there is any doubt as to whether the occurrence is reportable, an MOR should

be submitted.

https://aviationreporting.eu/



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2.7.6 The investigation will be overseen by the Head of Design (HoD). The investigation itself will be carried out by the Head of Independent System Monitoring, however it can be delegated to an independent person with suitable investigation or auditor skills if required.

2.7.7 If it is determined that the occurrence is classified as a non-reportable occurrence,

it should be determined whether STC Twenty One Ltd will submit a VOR. 2.7.8 The occurrence investigation will identify the root cause, corrective and

preventative actions. The root cause analysis should ensure that the root of the problem is reached. This may be found using Events and Causal Factors Analysis (ECFA).

2.7.9 The HoD after consultation with the reporter, will complete the occurrence

investigation by signing the Approved by HoD section of S21.2.33.REP.024. Findings and proposed corrective actions will be established using the guidelines set out in 21.A.3A. Any required corrective actions shall be transmitted through the Service Bulletin Procedure.

2.7.10 For MORs and VORs an initial update will be sent within 30 days of the initial

submission and the occurrence will be closed within 3 months. For MORs and VORs the final written report with findings and proposed corrective actions will be sent via the portal.

2.7.11 The HoD shall have full responsibility to advise the manufacturer, operator and

maintenance organisation of any reportable defects found. This is especially important where an occurrence has been discovered internally.

2.7.12 The HoD, will act as primary liaison with the Authority, manufacturer, operator,

maintenance organisation and reporter until such time as the defects have been resolved or primary responsibility for solving the defect has been transferred.

2.7.13 The occurrence assessment will recommend the nature of the corrective action

and whether or not such action should be classified as mandatory by the Authority. If agreed mandatory, the Authority will issue an Airworthiness Directive stating the mandatory corrective or necessary terminating action. Mandatory and non-mandatory corrective action will be distributed using a Service Bulletin Procedure.

2.7.14 The HoD, using procedure 2.10, as a guide, should determine if the corrective and

preventative actions will require a re-classification to the design change / repair. 2.7.15 In addition to Regulation (EU) 376/2014 and 2015/1018, there is Guidance

Material to 376/2014 and General Acceptable Means of Compliance AMC 20-8, ref. GM 21.A.3A(b).



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Process Flow Chart

EVENT Determined internally or reported by an external organisation / individual

OCCURRENCES Reportable or Non-Reportable

(EU) 376/2014

REPORTABLE OCCURRENCE Classified as an occurrence iaw (EU) 376/2014 or voluntarily reported by

STC Twenty One Ltd

NON REPORTABLE

NON MANDATORY ACTION Implement Corrective Action(s) & Issue Service Bulletin (if required).

MANDATORY ACTION Implement Corrective Action(s)

& Issue Service Bulletin. Possible Airworthiness

Directive

72 HOURS Report to

aviationreporting.eu

OCCURRENCE INVESTIGATION S21.2.33.REP.024

ACTION Determine Root Cause, Corrective

Actions & Preventative Actions

http://www.aviationreporting.eu/index.php?id=190&no_cache=1



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References: 2.23 Service Bulletin Procedure 2.33 Hazard, Safety, Maintenance Analysis and Continued Airworthiness

Procedure UK CAA Publication CAP382 Regulation (EU) 2015/1018, Regulation (EU) 376/2014, guidance material to 376/2014, AMC20-8, 19Taviationreporting.eu19T, Part 21.A.3A, 21.A.3B(c), 21.A.4(b), 21.A.109(a), 21.A.118A(a), 21.A.265(e), 21.A.451(a)1.





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2.8 Contractor & Sub-Contractor Selection Procedure

Purpose: To ensure contracted services such as design, testing, manufacture, aircraft

inspection and other specialist services are sought from suitable companies and organisations.

Scope: Identify and select suitable providers of required services in support of

certification of a design project. Definitions: A Contractor can be one of the following:-

1. A Subpart G Approved Production Organisation (POA) 2. A Subpart J Approved Design Organisation (DOA) 3. A Part 145 Approved Maintenance Organisation (MOA)

A Sub-contractor can be one of the following:-

1. A design company without Subpart J approval (DO) 2. A Test House (used for the demonstration of compliance) 3. An individual e.g. CVE

Procedure: 2.8.1 STC Twenty One Ltd will only utilise contractors that meet the definition above.

Reference will be made to the Authority, or Agency, website to ascertain the currency of their approval.

2.8.2 Sub-Contract Test houses will only be selected where they are being used for the

demonstration of compliance. Where testing is for information, such as DO-160, the test house will not fall under STC Twenty One procedures.

2.8.3 STC Twenty One Ltd will utilise sub-contractors chosen from Design Manual,

ST21/DOA/HB3 procedure DP110. 2.8.4 Individuals will be assessed by the HoD or HOOOA by interview applicable to the

selected field of experience. 2.8.5 A sub-contractor (other than an individual) will be selected for inclusion in

accordance with Design Procedure DP110. 2.8.6 The Design Assurance Audit may be by a physical audit of the sub-contract

organisations premises and procedures (see procedure 2.2) to interface with STC Twenty One Limited procedures. For organisations having provided sub-contract services to STC Twenty One Limited prior to CAA DOA approval, these



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organisations may provide a self-audit return using STC Twenty One Limited Vendor Audit/Self Audit Checklist form S21.AUD.REP.032.

2.8.7 Liaison with the contractor/sub-contractor will be maintained in accordance with

procedure 2.9. STC Twenty One Limited may develop and agree alternate interface procedures with the contractor/sub-contractor if derogations are required to those procedures stated in procedure 2.9. The interface procedures must be agreed by the HoD.

References:

2.2 Audit of Design Organisation Procedures 2.9 Liaison between STC Twenty One Ltd and the Selected Contractor 2.21 Test Plan Procedure DP110 Sub-Contract Selection Procedure

Part 21.A.33(b), 21.A.239(c), 21.A.243(b), 21.A.257, 21.A.439, 21.A.441, 21.A.451(a)1.



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2.9 Liaison between STC Twenty One Ltd and the Selected Contractor & Sub-Contractor

Purpose: To clearly define the communication required between STC Twenty One Ltd and

the selected Contractor / Sub-contractor. Scope: From the selection of a Contractor / Sub-Contractor through the final release of

the product or parts to responsibilities for continued airworthiness. Definitions: A Contractor can be one of the following:-

1. A Subpart G Approved Production Organisation (POA) 2. A Subpart J Approved Design Organisation (DOA) 3. A Part 145 Approved Maintenance Organisation (MOA)

A Sub-contractor can be one of the following:-

1. A design company without Subpart J approval (DO) 2. A Test House (used for the demonstration of compliance) 3. An individual e.g. CVE

Procedure: 2.9.1 Once a contracting organisation has been chosen in accordance with the

Contractor & Sub-contractor Selection Procedure (See Procedure 2.8), it must be ensured that adequate liaison occurs between the two organisations throughout the duration of the contract and for onward continued airworthiness.

2.9.2 The following arrangement forms will be put in place, prior to work being carried

out by the Contractor / Sub-contractor: DOA - POA form S21.2.9.REP.001 DOA - DOA form S21.2.9.REP.002 DOA - Individual form S21.2.9.REP.003 DOA - MOA form S21.2.9.REP.004 DOA - DO form S21.2.9.REP.006 DOA - DO/MOA form S21.2.9.REP.005 DOA - Test House form S21.2.9.REP.007 2.9.3 Where an MOA-DOA arrangement cannot be put in place a standard ‘Required

Responsibilities’ Email will be issued by STC Twenty One Ltd, outlining the minimum requirements / regulations that need to be complied with.



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2.9.4 It is acceptable to use equivalent forms issued by a POA/DOA/MOA, provided they cover the following paragraphs of Part 21; Part 21.A.3A, 3B, 4, 105, 118A, 119, 120A, 120B, 239, 804.

2.9.5 Individual STC Twenty One Ltd templates should be reviewed to ensure that the

correct procedures have been referenced. Where a POA is supplying the DOA-POA arrangement, refer to STC Twenty One Ltd template S21.2.9.REP.001 for applicable references.

2.9.6 Suitable signatories for the arrangement are the Head of Design, or Head of Office

of Airworthiness. 2.9.7 In the case of an individual, a contract tailored to the scope of work will be drafted

and signed by the contracted individual and the Head of Design or Accountable Manager.

2.9.8 Where an organisation carrying out production does not hold a subpart G approval,

an arrangement form will not be issued however a contract tailored to the scope of work including methods of communication and conformity, based on the intent of 21.A.122 and 21.A.133, will be drafted and signed by the contracted individual and the Head of Design or Head of Office of Airworthiness. Typically, the production of parts from a non-POA will be limited to test articles (see also procedure 2.21) unless agreed otherwise by the Authority.

2.9.9 Test Specimens shall be manufactured and conformed in accordance with

procedure 2.21. 2.9.10 Installation/manufacturing drawings issued to the POA/MOA shall be

accompanied with a Statement of Approved Design (SADD) (S21.2.46.REP.035). Drawings shall be issued in accordance with Drawing Issue Procedure (See Procedure 2.39).

2.9.11 Should an error be found in, or a change be required to, the STC Twenty One

Limited drawings or reports during manufacture/testing, the contractor/sub-contractor, after consultation with STC Twenty One Limited, will raise a Design Query Note (See Procedure 2.32) to resolve the error or action the change. If a manufacturing process or fabrication error is made, a Concession Application (See Procedure 2.31) will be submitted to the STC Twenty One Limited. STC Twenty One Limited will provide a repair scheme (see Procedure 2.45) prompted by the Concession application if appropriate. Where the part cannot be salvaged, the contractor will be required to destroy the manufactured part.

2.9.12 The DQN or Concession Application, as appropriate, shall be submitted to STC

Twenty One Ltd for processing. After processing by STC Twenty One Limited



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Design Department, the signed DQN or approved Concession will be returned to the contractor, detailing the required action.

2.9.13 Anything discovered by the MOA/POA affecting the manufacturing or supply

of the item, prior to, during or after the item is manufactured or released is to be communicated to the Head of Design at STC Twenty One Ltd as soon as possible. STC Twenty One Ltd, as Design Authority, will determine the implications on continued airworthiness and advise the MOA/POA Design/Quality Assurance Department of its findings and actions.

2.9.14 Anything discovered by the contracting DOA/MOA/POA affecting continued

airworthiness or safe flight shall be reported to STC Twenty One Limited (See procedure 2.33). In the case of a reportable occurrence, procedure 2.7 will be followed.

2.9.15 Any revisions to the design emanating from STC Twenty One Ltd will be conveyed

to the POA via Drawing Issue Procedure 2.39. 2.9.16 Upon receipt of signed agreement by both parties, an electronic copy is to be saved

within the Public Drive/Interface Arrangements under the appropriate folder for the arrangement.

References: 2.7 Reporting of Defects to CAA/Operators/Manufacturers 2.8 Contractor Selection Procedure 2.18 Document Issue Procedure 2.21 Test Plan Procedure 2.31 Concession Procedure 2.32 Design Query Note (DQN) Procedure 2.33 Hazard, Safety, Maintenance Analysis and Continued Airworthiness Procedure 2.39 Drawing Issue Procedure 2.42 Drawing Change Notice Procedure 2.43 Statement of Approved Design Data DP110 Sub-Contract Selection Procedure Part 21.A.4, 21.A.33(b), 21.A.109(a), 21.A.118A(a), 21.A.133(c) & AMC,

21.A.165(e)(f)(g), 21.A.239(c), 21.A.243(b), 21.A.257, 21.A.439, 21.A.441, 21.A.451(a)1



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2.10 Change or Repair Classification Procedure Part 21

Purpose: To detail the procedure for Classifying a change or repair to a product in

accordance with Part 21.A.91 and the associated GM. This procedure ensures that there is an acceptable and effective process for the submittal of data to confirm that the change complies with the applicable specifications and has no unsafe feature(s).

Scope: From the identification of a proposed change or repair through the compilation of

a classification form, to its classification and subsequent filing. Definitions: A Minor change/repair is one that has no appreciable effect on the mass, balance,

structural strength, reliability, operational characteristics, noise, fuel venting, exhaust emission, operational suitability data or other characteristics affecting the airworthiness of the product.

A Major change/repair is a change to the type design that is judged to have an

appreciable effect on other characteristics affecting the airworthiness of the product. Environmental Protection – Consists of noise and emission requirements. Procedure 2.51 to be followed. Operational Suitability Data (OSD) – Consists of data that is necessary for the safe operation of aircraft. Procedure 2.43 to be followed.

Procedure: Classification Compilation 2.10.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.10.2 A classification to a change/repair is made when all data necessary to identify and

agree the design specification becomes available. The classification will determine whether the change or repair is an STC/Major Repair or a Minor change/repair. This procedure is followed for changes/repairs to existing STCs.

Note: The data necessary may include, for instance, the conclusion from a

technical report completed following procedure 2.52. Such report must be referenced in the Justification section(s) of the Classification Checklist.



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2.10.3 A change/repair is classified as either ‘Minor’ or ‘Major’ in accordance with Part 21.A.91 (and associated GM to Part 21.A.91), Part 21.A.435 (and associated GM to Part 21.A.435 in the case of repairs), the flow chart contained in this procedure, and using STC Twenty One Limited Form S21.2.10.REP.003 ‘Classification Checklist’ (or equivalent section of the Repair Form S21.2.45.REP.001) shall be used to ensure a consistent, traceable classification procedure.

2.10.4 The justification column of STC Twenty One Ltd Form S21.2.10.REP.003,

Classification Checklist (or equivalent in the Repair Document), shall, where not otherwise obvious, document the reasons for a classification decision (in accordance with GM 21.A.91 / GM 21.A.435).

2.10.5 If there is any doubt as to the classification of a change/repair, advice of the

Authority will be sought. 2.10.6 A change classified as Major will require STC Twenty One Ltd to apply to the

Authority for a Supplemental Type Certificate (See Procedure 2.17). 2.10.7 A change classified as Major to an existing STC owned by STC Twenty One Ltd will

require an application to the Authority to approve an amendment to the STC (See Procedure 2.17).

2.10.8 A change or repair classified as Major to an existing STC not owned by STC Twenty

One Ltd will require an application to the Authority to approve a stand-alone STC, or Major Repair Approval. (See Procedure 2.17 or 2.45 respectively).

2.10.9 A change or repair classified as Minor will be approved by STC Twenty One Ltd.

(See Procedure 2.15 or 2.45 respectively). 2.10.10 A repair classified as Major to an STC owned by STC Twenty One Ltd can be

approved by STC Twenty One Ltd in accordance with procedure 2.45 and recorded in STC Twenty One Ltd Repair Document (S21.2.45.REP.001).

Changes to a Design Change 2.10.11 If a change to a design change is sought, the change must be classified in

accordance with this procedure. 2.10.12 The Classification Checklist (S21.2.10.REP.003) is to be followed for changes to a

design change. The latest issue of the form is to be used. 2.10.13 The Classification Checklist (S21.2.10.REP.003) is to be raised in issue and

completed in its entirety to document the change to the design change. If a later issue of S21.2.10.REP.003 is available, the latest form must be used.



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2.10.14 The author is to explicitly define the reason for the change within the main text.

NOTE: The purpose of a raise in issue above is not to re-classify the original design change but is to document a revision to the existing design change. A re-classification to the original design change is to be accomplished in accordance with the re-classification section.

2.10.15 Notwithstanding the above, the below permits alleviation from 2.10.11 where the

criteria of an ‘Amendment’ is met. In such instances, any associated Design Query Note must document the justification for the classification.

2.10.16 A change to a design change may be categorised as either an Amendment or

Deviation, as defined below. 2.10.17 Amendment – is an alteration to a design change where there is no fundamental

variation to the basic design or alteration to the design change certification basis or limitations. Typically, an Amendment could be due to, but not limited to, the following examples: a Correction of a typographical error.

b Correction to an engineering drawing or instruction, where the original intent of the drawing / instruction is not altered.

c Introduction of equivalent or alternative parts or materials that do not require reassessment, e.g. alternative wires or contacts, alternative materials or fasteners, as explicitly stated in the TC-Holder Electrical Standard Practices or Structural Repair Manual.

d An alteration to a testing method that does not alter the demonstration of compliance made under the original Design Change / Repair.

e Addition of an aircraft MSN where no technical / airworthiness assessment is needed.

2.10.18 An Amendment can be actioned, resulting from the following:

a Receipt of a DQN,

b Receipt of a Concession Application,

c Customer Request,

d Continued Airworthiness Feedback Form,

e Internal correction of an error. 2.10.19 An Amendment is recorded by way of a revision to the affected document. The

affected document should clearly define the reason for the change and include the



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following wording “This revision is classified as an Amendment in accordance with Procedure 2.10”.

2.10.20 The Master Document List may require revision as a consequence of the

amendment. 2.10.21 Deviation – is an alteration to the basic design change or a change to the

limitations. A Deviation is to be used for all cases where an Amendment cannot be utilised.

2.10.22 A Deviation is referred to as a change to a design change, which must be classified

per the criteria of Procedure 2.10 and a Major or Minor classification made via a DQN (procedure 2.32). If further investigation or justification is required by the HOOOA, the Classification Checklist is to be raised in issue with details of the change, including justification, to be recorded.

2.10.23 A Deviation can be actioned, resulting from the following:

a Receipt of a DQN,

b Receipt of a Concession Application,

c Customer Request,

d Continued Airworthiness Feedback Form,

e Internal correction of an error.

2.10.24 A Deviation is recorded by way of a revision to the appropriate documents. The affected amendment record should clearly define the reason for change.

Rules for a Change to a Design Change 2.10.25 Amendments are by default classified as minor. 2.10.26 Amendments may be made to minor or major design changes and are approved

under DOA approval reference UK.21J.0198. 2.10.27 A Deviation may be major or minor depending upon the outcome of the

classification.

2.10.28 For Minor design changes, only changes classified as ‘Minor’ per 21.A.91 / 21.A.435 and Procedure 2.10 are permitted.

2.10.29 A Major Deviation cannot be applied to a Major Repair Approval. In this case, a

new repair approval is required.



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2.10.30 For Major Changes, changes classified as ‘Minor’ or ‘Major’ in accordance with

21.A.91 and Procedure 2.10 are permitted.

NOTE: If any doubt exists as to the applicability of a Deviation, advice must be sought from the HOOOA (or deputies).

Approval of a Change to a Design Change 2.10.31 Approval of Amendments are through document approval procedures. 2.10.32 Approval of Deviations are through design change approval procedures. 2.10.33 A minor Deviation (to a minor change) is approved under DOA approval reference

UK.21J.0198. 2.10.34 A major Deviation (to a major change) is approved as a revision to the STC by the

Authority. In this instance a separate application will be made to the Authority using UK CAA Form SRG1726NR quoting the design change reference number for the Deviation and the original STC reference to which the Deviation applies.

Environmental Protection 2.10.35 Procedure 2.51 must be followed for all classifications in order to determine if

environmental characteristics are affected. Where environmental characteristics are affected, further investigation or discussions with the Authority will be required before the change can continue.

Operational Suitability Data (OSD) 2.10.36 Procedure 2.43 must be followed for all classifications in order to determine if OSD

is affected.

2.10.37 Some OSD changes, or potential impact to, OSD data may be outside of STC Twenty One Ltd terms of approval. In these cases, discussions with the Authority will be required before the change can continue.

Classification Approval 2.10.38 Once Part A of the Classification Checklist is completed, and signed, it will be

submitted to the Head of Office of Airworthiness for review.

2.10.39 The HOOOA (or deputies), will review the Classification Checklist and endorse the classification of the change/repair. This will be done using 21.A.91, 21.A.95,



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21.A.97 and 21.A.435 as a guide, together with previous experience and good judgement. Once satisfied that the Initial Classification is correct Part B of the form will be signed.

Re-Classification 2.10.40 A Design Change may be re-classified and then endorsed by the Head of Office of

Airworthiness. This action is recorded in a reissue of the Classification Checklist. The design change re-classification may result from any one of the examples below:

1. Advice has been sought from the Authority and they have agreed the

classification as per 2.10.4 of this procedure.

2. The customer has specifically requested an STC even though the change is classified as minor.

3. The design change/repair cannot be classified using the classification criteria listed in the classification checklist form.

2.10.41 If proposing a reclassification to an already classified Major change, the Authority must be contacted in order that they may take the responsibility in re-classifying the change.

2.10.42 The completed checklist shall be filed in the appropriate binder located in the

design office. References: 2.15 Minor change/repair Approval Procedure 2.17 Major change/repair Approval Procedure 2.45 Repairs 2.51 Environmental Protection 2.52 Wireless LAN Classification Procedure

Part 21.A.91, & GM 21.A.91, 21.A.95(b), 21.A.97(a), 21.A.117, 21.A.263(c)(1),

21.A.435



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CHANGE CLASSIFICATION PROCEDURE Classification Process – see procedure 2.45 for repair classification

Change in Type Design

Classification of Design Change 21A.91 Goals - determine approval route

- assess effect on airworthiness

Are any of the following 21A.91 criteria met? - appreciable effect on mass - appreciable effect on balance - appreciable effect on structural strength - appreciable effect on reliability - appreciable effect on operational characteristics of the product - appreciable effect on noise, fuel venting and exhaust

emissions - appreciable effect on airworthiness

Any of the following criteria met? - adjustment of certification basis - new interpretation of the requirements used for the TC

basis - aspects of compliance demonstration not previously

accepted - extent of new substantiation data and degree of

reassessment and re-evaluation considerable - alters the limitations directly approved by the Authority - mandated by AD or terminating action of AD - introduces or affects function where failure condition

is catastrophic or hazardous

Request for reclassification

Authority decides classification

Any good reason to reclassify minor?

MINOR

MAJOR

NO YES

YES

YES

NO

See also Appendix A to GM 21.A.91 examples: 1. Structure 2. Cabin Safety 3. Flight 4. Systems 5. Propellers 6. Engines 7. Rotors and Drive Systems 8. Environment 9. Powerplant Installation



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2.11 Civil Change/Repair Record Procedure Purpose: To detail the requirements for the Civil Change/Repair Record. Scope: From the creation of a Change/Repair Number to the completion of the change or

repair record details. Definitions: None. Procedure: 2.11.1 Reserved. 2.11.2 Each Change/Repair record shall be numbered using S21.XX[ATA Chap]-XX[A/c

code]- followed by a sequential 4 digit number, beginning at 1000, e.g. S21.34-13-1000. The number is allocated from the STC Twenty One database.

2.11.3 When a design change/repair is completed and fully certified, closure should be

recorded in the database, which will also record the following information.

a. Change or repair reference number (as defined above) b. Title and brief description of change or repair c. Change or repair classification d. Date Allocated e. Date Completed

References: None



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2.12 Certification Programme, Establishment of Certification Basis and Compliance Checklist Procedure

Purpose: To define how a Certification Programme is compiled, checked, approved and

revised, in support of a Change to Type Design and to provide those items required by 21.A.15(b) and to evolve into Compliance Checklist, allowing for independent Verification

Scope: All Certification Programmes raised by STC Twenty One Limited. Definitions: None. Procedure: 2.12.1 For Changes, Certification Programmes are generated using form

S21.2.12.REP.006-MIN or S21.2.12.REP.005-MAJ as appropriate. 2.12.2 For major changes Certification Matrix Spreadsheet S21.2.12.REP.005-Major

Matrix may be used as a tool to generate the initial Certification Matrix, Compliance Demonstration Items (CDI) and to propose Level of Involvement (LOI).

2.12.3 Once compiled, the Certification Programme will be checked and approved by

Checker, Approver, CVE & HOOOA (or deputies), respectively. 2.12.4 The Head of the Office of Airworthiness has the responsibility to:

- Agree the proposed Certification Basis - Verify Compliance with Certification Basis

2.12.5 All Certification Programmes for Major Changes will be forwarded to the Authority

for review and agreement of the proposed Certification Basis and the proposed Level of Involvement. Authority agreement of the proposed Certification Basis and the proposed Level of Involvement will be provided per 21.B.100 and should be retained and may be referenced in subsequent revisions of the Certification Programme.

2.12.6 For all Certification Programmes, each re-issue only requires signatories applicable

to the changes from the previous issue.



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References: 21.A.19, 21.A.20(b)(c)(d), 21.A.31, 21.A.35(b), 21.A.93(b), 21.A.95, 21.A.97(b)(c)(d), 21.B.100, 21.A.101, 21.A.113(b)(c), 21.A.115(b)(d), 21.A.119, 21.A.239(a)1(b)(c), 21.A.257, 21.A.265(c)(d)



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2.13 Reserved



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2.14 Reserved



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2.15 Minor Change/Repair Approval Procedure Purpose: To ensure all changes/repairs deemed Minor are correctly submitted for approval

and subsequently approved. Scope: From the completion of a Certification Programme, through the co-ordination and

submission of the Minor change/repair data package to its approval. Definitions: None. Procedure: 2.15.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.15.2 A change/repair, classified minor under the Procedure 2.10, will be subject to the

following approval procedure. 2.15.3 A copy of the relevant Certification Programme, Airworthiness Compliance

Checklist and other supporting reports and data is to be collated. 2.15.4 All change/repair information is to be reviewed by an appropriate CVE to ensure

that compliance with all applicable requirements has been met and all paperwork is complete and correctly signed.

2.15.5 The change/repair package, after HOOOA (or deputies), has verified compliance in

accordance with procedure 2.12, the master document list is to be passed to the HoD (or deputies) to sign the Declaration of Compliance (Refer to Procedure 2.16 or 2.45). Prior to signing, all Design Office Instructions, Design Query Notes and Concessions are reviewed and, if applicable, noted in the Master Document List or Repair Document as applicable. The HoD (or deputies) will ensure that no new regulatory issues have been raised within industry. Any areas of uncertainty should be referred to the Authority for clarification.

2.15.6 The HoD (or deputies) will approve a minor design change by signing the Minor

Design Change Approval on the Master Document List form (Refer to Procedure 2.16).

2.15.7 The HoD (or deputies) will approve a minor repair by indicating the appropriate

approval sign off and by signing the declaration in the repair document, S21.2.45.REP.001).



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2.15.8 The above signing certifies that the change/repair complies with the relevant requirements, that no unsafe features have been identified and that all procedures specified in this Handbook have been complied with.

2.15.9 A copy of all relevant documents shall be issued in accordance with Procedures

2.18 and 2.40. 2.15.10 When the Minor Design Change/Repair has been approved, a Statement of

Approved Design Data (SADD) may be issued IAW STC Twenty One Limited Procedure 2.46.

2.15.11 . References: 2.5 Checker & CVE Selection Procedure 2.10 Change/Repair Classification Procedure 2.12 Certification Programme, Establish of Certification Basis and

Compliance Checklist Procedure 2.16 Master Document List 2.18 Document Issue Procedure. 2.39 Drawing Issue Procedure 2.45 Repairs 2.46 Statement of Approved Design Data Procedure Form S21.2.45.REP.001

Part 21.A.91, 21.A.93(b), 21.A.95(b), 21.A.105, 21.A.107, 21.A.109(a), 21.A.117(a), 21.A.118, 21.A.239(b), 21.A.263(c)(2), 21.A.433(a), 21.A.435(b), 21.A.443.



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2.16 Master Document List Purpose: A Change/Repair Master Document List (MDL) details all documents, including the

current revision state of each, that are required in support of the Change/Repair approval that is being sought.

Scope: Introduction and creation of a MDL. Definitions: None. Procedure: 2.16.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.16.2 For changes the MDL is to be compiled on form S21.2.16.REP.008. For repairs the

MDL will be included as part of the Repair Document, S21.2.45.REP.001, but will follow the intent of this procedure.

2.16.3 Each required document is identified and would typically include:

a) Certification Documents (e.g. CLAS, PROG) b) Technical Reports (e.g. ELA, Stress) c) Drawings d) Test Plans/Test Reports e) Supplement Manual / ICA f) Accomplishment Instruction g) Manual Supplements (e.g. AFMS, MMEL)

2.16.4 The MDL will be split into 4 sections as follows: a) Section 1 – Documents required for installation. This will be further

split into Drawings and Reports. b) Section 2 – Documents required for manufacture. This will generally

consist of drawings but may also list reports where required. c) Section 3 – Certification documents retained by STC Twenty One

Ltd. This could include the CLAS, PROG and EAFs. d) Section 4 – Certification documents for the Operator. This could

include the TEC, MMEL, FMS. 2.16.5 The MDL will contain the names and signatures of the compiler and independent

checker and approver, the Declaration of Compliance required by 2.15 or 2.17, and the approval required by 2.15 or CAA approval reference, as applicable.



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2.16.6 If documents are to be used across more than one section, they should be listed in each section as required.

2.16.7 A revision to any document or drawing referenced in the MDL will require an up-

issue to the MDL. This excludes the Supplement Manual where the revision level is generally listed as ‘latest’.

References: Part 21.A.20(d)(e), 21.A.31, 21.A.95(f); 21.A.97(d), 21.A.239(a)1, 21.A.263(c)2,

21.A.265(d)



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2.17 Major Change/Repair Approval Procedure Purpose: To ensure all changes/repairs deemed Major are correctly submitted for approval

and subsequently approved. Scope: From the completion of a Certification Programme, to the submission of the

Change/Repair Approval data package to the Authority. Definitions: None. Procedure: 2.17.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.17.2 A change/repair, classified major in accordance with Procedure 2.10 and

Procedure 2.45 respectively, will be subject to the following approval procedure. 2.17.3 For major changes and repairs to be approved by the Authority, application is to

be made using the appropriate Authority forms and procedures together with the relevant fees (refer to the Authority website). In accordance with 21.A.93(c), an application for a change to a large aircraft or large rotorcraft is valid for 5 years and for other applications for 3 years. If approval has not been obtained, or it is evident that it won’t be, an extension or a new application should be obtained.

2.17.4 A copy of the relevant Certification Programme, Compliance Checklist and other

supporting reports and data is to be collated. 2.17.5 All change/repair information is to be reviewed by the appropriate Compliance

Verification Engineers to ensure that compliance with all applicable requirements has been met and all paperwork is complete and correctly signed.

2.17.6 The changed product must meet the applicable type certification basis, operational

suitability data certification basis and environmental protection requirements, as specified in the applicable Certification Programme (Procedure 2.12).

2.17.7 The change package, after HOOOA (or deputies), has verified compliance in

accordance with procedure 2.12, the master document list is to be passed to the HoD (or deputies) to sign the Declaration of Compliance (Refer to Procedure 2.16). Prior to signing, all Design Office Instructions, Design Query Notes and Concessions are reviewed and, if applicable, noted in the Master Document List. The HoD (or deputies) will ensure that no new regulatory issues have been raised within industry. A copy of the signed Declaration of Compliance is issued to the Authority serving as a positive statement that the design change complies with all relevant



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certification, operational suitability and environmental protection requirements, that no unsafe features have been identified and that handbook procedures have been followed.

2.17.8 For Major repairs not being approved by STC Twenty One Ltd, procedure 2.17.3,

2.17.6 and 2.17.7 will be followed, except that information will be included within a Repair Document (S21.2.45.REP.001).

2.17.9 For Major repairs being approved by STC Twenty One Ltd, after final review by the

Office of Airworthiness, the Repair Document (S21.2.45.REP.001) will be submitted to the HoD (or deputies) for signing the Declaration of Compliance and Approval statement. Prior to signing, all Design Office Instructions, Design Query Notes and Concessions are reviewed and, if applicable, noted in the Repair Document. The HoD (or deputies) will ensure that no new regulatory issues have been raised within industry.

2.17.10 For Major changes/repairs being approved by the Authority , approval is by issue

of the appropriate certificate (STC or Repair Approval). 2.17.11 Major amendments must be approved by the Authority in accordance with this

procedure. Minor amendments are allowed. 2.17.12 When the Major Design Change/Repair has been approved a Statement of

Approved Design Data (SADD) may be issued IAW STC Twenty One Limited Procedure 2.46.

2.17.13 An STC may be revoked under the following circumstances: STC Twenty One

Limited surrenders the STC, by way of the STC Twenty One Limited Part 21 Subpart J DOA approval ceasing to be in force or revoked by the Authority in accordance with procedures laid down by them. Upon surrender or revocation, the supplemental type-certificate shall be returned to the Authority.

References: 2.5 Checker & CVE Selection Procedure 2.10 Change/Repair Classification Procedure 2.12 Certification Programme, Establish of Certification Basis, and

Compliance Checklist Procedure 2.16 Master Document List 2.18 Document Issue Procedure.

2.19 Approved Document filing Procedure 2.39 Drawing Issue Procedure 2.45 Repairs 2.46 Statement of Approved Design Data



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Part 21.A.20(e), 21.A.91, 21.A.93, 21.A.97(a)(b)(c), 21.A.113, 21.A.115(a)(c), 21.A.117(b)(c), 21.A.118A(a), 21.A.118B, 21.A.120A, 21.A.239(b), 21.A.265(d), 21.A.432C, 21.A.433, 21.A.435(b), 21.A.443, 21.A.451(a)1.



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2.18 Document Issue Procedure Purpose: To control the issue of approved and prototype documents. Scope: From identifying the need to issue a document, (excluding drawings) through its

copying, to its issue. Definitions: Approved Documents - Approved documents are those that form part of or

support an approved change/repair or certification documents that have been reviewed by the Office of Airworthiness and all relevant signatures applied.

Procedure: 2.18.1 It is to be established in conjunction with the Head of Design whether the

documents are to be issued as prototype or fully approved and to whom. 2.18.2 For documents issued as prototype, each page of the document is to have the Issue

number at the top of the page preceded by the letter “P”. 2.18.3 The documents will be issued via electronic transfer and a record kept in the design

office, as per DP102. References: 2.19 Document Filing Procedure DP102 – Document Distribution Part 21.A.441(b), 21.A.443, 21.A.449, 21.A.451(a)1(b)1



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2.19 Approved Document Filing Procedure Purpose: To control the filing of approved documents. Scope: From the issue of an approved document to its filing. Definitions: A document for the purpose of this procedure is any that STC Twenty One Limited

approves, or otherwise uses, in support of a design change, other than a drawing. Procedure: 2.19.1 All original change documents, reports (Design and Test), and certification data is

electronically stored on a cloud-based server to provide the information necessary to ensure continued airworthiness of the product or change.

2.19.2 All change documentation will be retained for as long as the product remains in

service and, afterwards, until such time as may be agreed with the Authority. 2.19.3 All documents shall be at the disposal of the Authority. 2.19.4 During development of a design change, all documents are stored on the relevant

design change sub-directory of the Project directory on the design office server. The server is backed up via a cloud-based service.

2.19.5 Upon completion of a design change, electronic (pdf) versions of all approved

documents are filed under the design change sub-directory of the Archive directory on the Design Office server. The server is backed up via a cloud-based service.

References: DP104 – Design Change/Repair Job Card Process Part 21.A.105, 21.A.109(a), 21.A.118A(a), 21.A.447, 21.A.451(b)1, 21.A.729



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2.20 Design Report (DES) Procedure Purpose: The Design Report is used for any Design Office document generated as a technical

response to a request for quotation, a compliance report for a company-designed system or a technical investigation report.

Scope: From the compilation of a Design Report to completion. Definitions: T None. Procedure: 2.20.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.20.2 All Design Reports shall be recorded on STC Twenty One Ltd Form

S21.2.20.REP.009. 2.20.3 The change/repair number generated from the Civil Change/Repair Register

(database) shall be entered on the Design Report Form front sheet if the design report being generated is associated with a Design Change/Repair. If the design report being generated is not associated with a Design Change/Repair, then “Not Applicable” will be annotated on the Design Report Form front sheet. The Design Report sequential serial number is allocated from the database. The Design Report sequential serial number shall be in the form of S21.DES-XXXX, where XXXX is a 4-digit serial number.

References: None.



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2.21 Test Plan Procedure Purpose: A Test Plan documents a test procedure that will be used to demonstrate that a

component or system satisfies relevant airworthiness and environmental protection requirements, or any other need, as determined by STC Twenty One Ltd. The results and conclusions from the testing are subsequently documented in a Test Report (See Procedure 2.22).

Scope: From the compilation of a Test Plan to its issue. Definitions: Test Article – A test article generally refers to an item of equipment, such as LRU,

or a product i.e. the aircraft. Test Specimen – A test specimen refers to an item that must be manufactured

specifically for test. Such as flammability test samples. Procedure: 2.21.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.21.2 All test plans shall be recorded on STC Twenty One Ltd Form S21.2.21.REP.010. 2.21.3 The Test Plan shall list, where applicable, the airworthiness and environmental

protection requirements. Where the testing is to demonstrate compliance with certification requirements, these will be directly, or indirectly (e.g. CRI, AMC), identified in the Certification Programme.

2.21.4 If a test specimen is required, it shall be fabricated / manufactured to a drawing /

specification approved by STC Twenty One Limited and be subject to a conformity inspection prior to the test being performed.

2.21.5 In all cases, STC Twenty One Limited has full responsibility to ensure conformity of

test specimens and articles. 2.21.6 The inspected test specimen shall be accompanied by either:-

a. Where a test specimen is manufactured by a POA - An Authorised release certificate (Form 1),

Note: The Form 1 must be sent to and retained by STC Twenty One Ltd within the applicable test report. Where applicable, ensure that procedure 2.8 and 2.9 are followed, and that a Statement of Approved Design Data (for test) is issued in accordance with procedure 2.46.



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b. Where a test specimen is manufactured in the USA by an organisation

having an appropriate FAA delegation, but not as part of an FAA STC project – An FAA form 8130-9 (Statement of conformity) listing the test article(s) conformed;

Note: The 8130-9 must be sent to and retained by STC Twenty One Ltd within the applicable test report.

c. Where a test specimen is manufactured by an organisation other than

defined in a) and b) above – STC Twenty One Limited form S21.2.21.REP-037 ’Conformity Inspection’ shall be completed. Copies of the completed form are retained within the design office filing system. Conformity Inspections are required to be carried out by an appropriate CVE. This function can be delegated, by the Head of Office of Airworthiness, to a person that the Head of Office of Airworthiness has determined to be acceptable, and which allows for conformity to be demonstrated. Refer to DP130 for further guidance.

2.21.7 Prior to the commencement of a test:-

a. The proposed test facility (MoC 4 testing only) shall be agreed by STC Twenty One Limited in accordance with procedures 2.8 and 2.9. This should be recorded on the test plan form. Refer to DP110 for approved test houses and further test house approval requirements.

b. A CVE, or delegated representative, shall be selected to witness the test.

Note: If a delegated individual is used to witness the test, they must be selected and approved in writing by the CVE or HoOoA. The use of a delegate must be recorded in the test report by virtue of their signature in the test witness block.

Note: In the case of approved test houses listed in DP110 it is permissible to not list a CVE or a delegated representative within the test plan as this is not always known.

c. The Test Witness shall check that the test article is in conformity. In the case

where the modified aircraft or aircraft system is tested the Test Witness shall record the issue or date of the MDL/DOI/SB/design data. The means of conformity shall also be recorded, e.g. Form 1 reference number, signed task card reference, CRS, etc. The Test Plan includes the facility for recording this data prior to the test, such that it is included in the subsequent report.



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d. In the case of a deviation, the Test Witness shall ensure that Design Query Notes, Concessions are correctly completed and acceptable for the required testing, such that the test results will not be affected. The Test Plan includes the facility for recording this data prior to the test, such that it is included in the subsequent report.

e. The Test Witness shall ensure that the test equipment and all measuring

equipment used for tests are adequate for the test and are appropriately calibrated. The Test Plan includes the facility for recording this data prior to the test, such that it is included in the subsequent report.

f. The Test Plan shall include the following declaration: “The test

specimen/article and test equipment conform to the design data/test plan as verified above. Any deviations listed will not adversely affect the test results.”

2.21.8 Under some circumstances it may be acceptable to independently review test data

via remote video or the review of video test data, subject to the acceptance of the Head of Office of Airworthiness. If doubt exists, advice will be sought from the Authority as early as possible in the project. The Test Plan shall include appropriate instructions.

2.21.9 STC Twenty One Limited shall allow the Authority to make any inspection

necessary to check compliance with the inspection of test specimens and test facility equipment requirements.

2.21.10 The Authority has the right to review any report and make any inspection and to

perform or witness any flight and ground test necessary to check the validity of the declaration of compliance submitted by the applicant under point 21.A.20(d), and to determine that no feature or characteristic makes the product unsafe for the uses for which certification is requested.

2.21.11 For tests performed or witnessed by the Authority, STC Twenty One Ltd will submit

a statement of compliance. No change relating to the test that would affect the statement of compliance may be made to a product, part or appliance between the time compliance is shown and the time it is presented to the Authority.

2.21.12 Where required the Test Plan will state whether the test is to be witnessed by STC

Twenty One Ltd, delegated organisation/individual and/or CAA.



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References: 2.8 Contractor & Sub Contractor Selection Procedure

2.9 Liaison between STC Twenty One Limited and the Selected Contractor 2.12 Certification Programme, Establish of Certification Basis and Compliance

Checklist Procedure 2.22 Test Report Procedure 2.46 Statement of Approved Design Data Procedure DP711 – Flammability, Heat Release and Smoke Density Testing DP710 – Structural Article Testing DP130 – Test Witnessing Part 21.A.33, 21.A.35(a)(b), 21.A.239(c), 21.A.257(b)



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2.22 Test Report Procedure Purpose: The Test Report is generated to record the results obtained from a Test Plan. It

also allows for Compliance Verification to be carried out where testing was required for the demonstration of compliance.

Scope: From the compilation of a Test Report to its issue. Definitions: None. Procedure: 2.22.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.22.2 All test reports shall be recorded on STC Twenty One Ltd Form S21.2.22.REP.011. 2.22.3 The Test Report is used to record the actions from the completed Test Plan. The

report should include a description of the test and a reference to the Test Plan. Configuration of the specimen and/or article is to be recorded, along with any details of calibrated equipment.

2.22.4 All reports are to contain a separate section detailing the showing of compliance

for airworthiness and environmental requirements and the conclusions as to whether compliance has been met. Any recommendations as a result of the testing should also be stated.

2.22.5 On completion of the test, the results are to be returned to STC Twenty One Ltd. 2.22.6 The final document sign off by the CVE will determine whether the report and

testing is acceptable and demonstrates compliance. 2.22.7 Where a Form 1 or 8130-9 is used for test specimen conformity, the test report

must contain the test article release documentation within an appendix (Ref 2.21.6).

References: 2.21 Test Plan Procedure Part 21.A.33, 21.A.35(b), 21.A.239(b)(c), 21.A.263



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2.23 Service Bulletin Procedure Purpose: A Service Bulletin is required when an alteration is made to an existing approved

change/repair. The Office of Airworthiness discharges its responsibility for continued

airworthiness and environmental protection through the medium of a Service Bulletin where remedial action is necessary. This may be concurrent with the issue of an Airworthiness Directive

Scope: From the compilation of a Service Bulletin to its issue. 27TDefinitions:27T None. 27TProcedure: 2.23.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.23.2 All Service Bulletins shall be recorded on STC Twenty One Ltd Form

S21.2.23.REP.012. 2.23.3 Each Service Bulletin shall be compiled in liaison with the Office of Airworthiness.

(See 1.7.3) 2.23.4 The front page of the Service Bulletin shall be signed by the compiler, Compliance

Verification Engineer, in accordance with the Approved Signatory Matrix (See Appendix 2) and approved by the Head of Design.

2.23.5 All Service Bulletins shall have the following headings in accordance with ATA 100:

a. Planning Information b. Effectivity c. Concurrent Requirements d. Reason e. Description f. Compliance g. Approval h. Manpower j. Weight and Balance k. Electrical Load l. References m. Other Publications Affected n. Material Information



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o. Material Price and Availability p. Re-identified Parts q. Tooling r. Accomplishment Instructions s. Instructions for continued airworthiness.

2.23.6 All Service Bulletins shall contain the following statement:

"The technical content of this document is approved under the authority of the DOA ref. UK.21J.0198”

References: 21.A.3A(a)(c), 21.A.3B(c), 21.A.265(e)(h)



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2.24 Equipment Qualification Procedure Purpose: To determine suitability and any limitations of use for equipment intended to be

installed in an aircraft as part of a design change. Such limitations are to ensure compliance with the applicable airworthiness requirements (typically, 2X.1301) of the design change and continued safe operation of aircraft.

Scope: An acceptable means of compliance where MoC 9 has been identified. Definitions: Avionic Equipment

Equipment for which its purpose is intended to operate the aircraft. These systems can include communication, navigation, display and management of multiple systems and flight control. Development Assurance Level (DAL) Development Assurance Level, also referred to as DAL or IDAL is a designation that is assigned to equipment (hardware or software) by the equipment manufacturer during the development phase. The DAL Level defines the rigour used according to the intended design goal. The DAL designation follows a similar methodology as per failure classifications in AMC to CS2x.1309 using Level A through E, with level A (catastrophic) being the most rigorous and level E (no safety effect) being the least rigorous. Declaration of Design and Performance (DDP) This is a summary document containing the definition and all relevant references of a piece of equipment. The DDP documents the declared equipment design characteristics, testing and manufacturing compliance with the applicable MOPS to which the equipment has been designed.



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Equipment For the purposes of this procedure the following terms can all be equivalent to the term ‘equipment’, since the various aerospace regulations use differing terms and are not standardised:

• Parts, • Appliances, • Article, • Component.

Article 3(d) of Regulation (EC) No. 216/2008 (the basic regulation) defines parts and appliances as any instrument, equipment, mechanism, part, apparatus, appurtenance, software or accessory, including communications equipment, that is used or intended to be used in operating or controlling an aircraft in flight including parts of an airframe, engine or propeller, or equipment used to manoeuvre the aircraft from the ground. Minimum Operational Performance Standard (MOPS) A Minimum Operational Performance Standard provides design standards for specific equipment(s). The term ‘equipment’ used in the context of MOPS includes all components and units necessary for the system to properly perform its intended function(s). MOPS describe typical equipment applications and operational goals and establishes the basis for required performance under the design standard. Standard Part A part manufactured in complete compliance with an established industry or Authority approved specification. Examples include, but are not limited to, National Aerospace Standard (NAS), Army-Navy Aeronautical Standard (AN), Society of Automotive Engineers (SAE), SAE Sematec and American National Standards Institute (ANSI). Alternatively, a standard part may be a component that has been defined for a specified purpose within Handbook 3. Type Certified Equipment Type Certified approved equipment e.g. equipment listed in the Illustrated Parts Catalogue (IPC) effective to the aircraft being modified.



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Technical Standard Order (TSO) A TSO is defined for this procedure as an approval given to equipment that complies with a MOPS accepted by a regulatory authority. The FAA issue TSO approvals, EASA issue ETSO approvals and UK CAA issue UKTSO approvals. In some cases, derogations to the MOPs are documented on the TSO as a limitation. Important Note: A TSO does not automatically give approval for installation; it is a means of demonstrating its suitability. Open Problem Reports (OPR) This is defined as a problem that has not been corrected at the time the software/airborne electronic hardware was certified. OPRs need to form part of any software review.

2.24.1 Overview:

2.24.1.1 The introduction of equipment to aircraft is approved by the Change, there is not a standalone approval of the equipment which allows installation.

2.24.1.2 Typically, equipment is informally reviewed during the compilation of the design

data and will be formally assessed during substantiation during the Change approval, such as:

• Functional Hazard Assessment/System Safety Assessment (CS

25.1309) • Structural Substantiation (for example, but not limited to, CS

25.561) • EMI/EMC Analysis/Testing (CS 25.1353) • Electrical Load Analysis (CS 25.1351) • Human Machine Interface Analysis (CS 25.1322) • Compliance Summary (Various) • Function Testing. (Various)

2.24.1.3 However, equipment qualification will need to be specifically addressed when

demonstrating compliance such as CS 25.1301(a) as a Means of Compliance (Moc 9) has been identified.

2.24.1.4 As per the holistic method, Equipment Qualification is a process which may include

means of compliance (MoC 0 thru MoC 7) at equipment level.

2.24.1.5 This procedure provides a formal means to document some of the considerations for the selection and suitability of the equipment where an MoC 9 has been identified.



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2.24.1.6 The equipment assessment will identify any limitations for the use of such

equipment whether it be manufacturer specified or on a qualification basis.

2.24.1.7 Equipment Assessments should be produced as early as practicable in the project to ensure that the performance standard and any limitations of use are communicated to design staff such that correlation can be maintained with the required design goals.

2.24.1.8 Important: The approval of non-TSO avionic equipment containing software and/or complex electronic hardware is limited to equipment with a DAL of D or E, where the analysed failure effect at the aircraft and/or system level correlates. The information contained within the TSO definitions should be noted when observing this limitation.

2.24.1.9 If the analysed failure effect at the aircraft level due to software/complex

electronic hardware failure and/or anomalous behaviour is one of ‘Minor’ or less severe, the use of non-TSO avionic equipment with a DAL of C or higher is permitted.

2.24.2 Procedure:

2.24.2.1 Standard Parts may generally be omitted from the formal assessment process as

they have been selected for a specific purpose based on a standard within the Design Data, i.e., nuts, bolts, washers, connectors, cables, etc, the use of which would be considered for suitability by the designer. However, a standard part which is being used in a novel application or outside of its normal environment must undergo assessment. Certain assemblies comprising of standards parts e.g. flexible pipes may still be subject to an assessment to ensure that they are adequate for the intended purpose/environment.

2.24.2.2 Type Certified approved equipment e.g., equipment listed in the Illustrated Parts Catalogue (IPC) effective to the aircraft being modified. These may not require an additional equipment assessment, dependent on the aircraft build standard, equipment modification standard and environment of the aircraft being modified is compatible with the equipment being installed and that the equipment is being utilised for a comparable purpose. Equipment of this nature will be identified within the Certification Programme.

2.24.2.3 Standalone Equipment Assessment Forms (EAF)(S21.2.24.REP.013) may be utilised for each item of equipment as a tool where Means of Compliance (MoC) 9 has been identified within the Certification Programme. This form is to be used as a guide only and is not intended to address all eventualities. The author of the EAF



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is responsible for determining the content is in line with level of assessment required dependant on functionality, criticality, complexity, novelty etc.

2.24.2.4 For Avionics Equipment, the DAL and any defined limitations shall be assessed to determine if they are appropriate to the intended use of the equipment, when considered at the aircraft level. Due to the increased complexity and criticality Avionics Equipment shall always be assessed using an EAF.

2.24.2.5 An Equipment Assessment Report (EAR) form (S21.2.24.REP.049) may be utilised

to group all of the assessments together.

2.24.2.6 The EAR allows for the use of Equipment Assessment Data Tables (EADT), which is a condensed Equipment Assessment Form.

2.24.2.7 The EAR will contain an Aircraft Equipment List (AEL) detailing equipment introduced under the Change. Depending on the complexity of the Change multiple EARs may be required i.e. by discipline.

2.24.2.8 The AEL, as a minimum, will list the part number, item name,

manufacturer/supplier, applicable engineering drawing and method of assessment.

2.24.2.9 Against each item an assessment method will be assigned, either EAF or EADT.

2.24.2.10 The EADT may be used when it meets the requirement defined in Figure 1. It is

also permissible to opt to complete an EAF in lieu of an EADT, it is not permissible to complete a EADT when an EAF is required.

2.24.2.11 Guidance for completing the EAF, EAR and EADT is contained within that specific document.



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Figure 1 - Assessment Selection Method



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References:27T Eurocae ED-12 / RTCA DO-178 Eurocae ED-80 / RTCA DO-254 Certification Memorandum CM-SWCEH-002, Software Aspects of Certification CM–SWCEH-001, Development Assurance of Airborne Electronic Hardware AMC 20-115 27TPart 21.A.239(c), 21.27TA.303, 21.A.305, 21.A.307 RTCA/DO-297 (Integrated Modular Avionics).



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2.25 Transfer of Airworthiness Responsibilities Purpose: This procedure deals with the transfer of STC Twenty One Ltd approved design

changes, and the continued airworthiness responsibilities, to a suitable legal entity.

Scope: Instructions on the transfer of a completed design change to a natural or legal

person. Definitions: Natural or Legal Person – Organisation approved under the Authority who can

hold an STC or Minor design change approval. TIP – Technical Implementation Procedures Procedure: 2.25.1 To be confirmed upon agreement of bilaterals and associated TIPs

References: Part 21.A.116.



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2.26 Technical Report Procedure Purpose: Technical Reports are raised to document technical assessments made in support

of a design. The conclusions made in the report shall be used in the substantiation of compliance with the airworthiness, operational suitability data and environmental protection requirements.

Scope: From the compilation of a Technical Report to its issue. Definitions: None. Procedure: 2.26.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.26.2 All Technical Reports shall be recorded on a Technical Report Form

(S21.2.26.REP.015). 2.26.3 The front page of the report shall be signed by the compiler, independent

Compliance Verification Engineer, in accordance with the Approved Signatory Matrix (See Appendix 2).

2.26.4 Typical Technical Report content:

a. A structural report should contain, as a minimum: (i) Introduction. (ii) Reference Documents. (iii) List of Reserve Factors. (iv) Applicable Airworthiness requirements. (v) Analysis. (vi) Conclusion(s).

b. A general report should contain, as a minimum:

(i) Introduction. (ii) Reference Documents. (iii) Applicable Airworthiness requirements. (iv) Analysis. (v) Conclusion(s).

c. A system safety assessment will be completed using DP206.

References: DP206 Compilation of System Safety Assessments Part 21.A.239(b).



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2.27 Reserved



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2.28 Design Office Instruction Procedure Purpose: Design Office Instructions may be used to detail investigative work or testing not

resulting in a product change. Scope: From the compilation of a Design Office Instruction to its issue. Definitions: None. Procedure: 2.28.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.28.2 All Company DOIs shall be recorded on a DOI Form (STC Twenty One Ltd Form

S21.2.28.REP.017). 2.28.3 The front page of the DOI shall be signed by the compiler and approved by relevant

Compliance Verification Engineer(s). 2.28.4 For all other DOIs the signatories are to ensure the instructions do not result in a

product change. 2.28.5 For DOIs that are required for test the DOI must be listed in the applicable test

plan. 2.28.6 All DOIs shall contain the following statement:

"The technical content of this document is approved under the authority of the DOA ref. UK.21J.0198”

References: 2.19 Approved Document Filing Procedure 2.31 Concession Procedure 2.32 Design Query Note Procedure 2.46 Statement of Approved Design Data Procedure Part 21.A.265(h)



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2.29 Flight Manual Supplement Procedure Purpose: To approve minor revisions to the Aircraft Flight Manual and Supplements. Scope: From the compilation of a Flight Manual Supplement to its issue. Definitions: AFM - Aircraft Flight Manual / Supplement, this generally refers to the original

document being revised. FMS – Flight Manual Supplement, this generally refers to the document that STC

Twenty One is producing. Revision – A revision to the Aircraft Flight Manual or Supplement is the wording

used by in GM 21.A.91 section 3.6. A revision to an AFM or Supplement should not be confused with an up-issue or amendment to a document.

Note. – Any AFM Revision (by issue or up-issue of an FMS) is a change under Part 21 and must be classified and approved in accordance with procedures 2.10 and 2.15 or 2.17.

Procedure: 2.29.1 Determine the need for a revision to the AFM following this procedure (2.29) or to

the FCOM following procedure 2.47, in accordance with CS 25.1581 and AMC 25.1581, in particular noting the following definitions from AMC 25.1581:

a) Aeroplane Flight Manual (AFM). An Authority approved document that contains information (limitations, operating procedures, performance information, etc.) necessary to operate the aeroplane at the level of safety established by the aeroplane’s certification basis.

b) Flight Crew Operating Manual (FCOM). A document developed by a manufacturer that describes, in detail, the characteristics and operation of the aeroplane or its systems.

2.29.2 All revisions to the Aircraft Flight Manual require a classification agreement signed

by the Head of Office of Airworthiness using Procedure 2.10 or using FMS Amendment Classification (FAC) Form (STC Twenty One Ltd Form S21.2.29.REP.036).

NOTE: GM to 21.A.91 gives examples of classifications to changes to Aircraft Flight Manuals Changes.

2.29.3 Reports to be completed in accordance with procedure 2.0, Report Completion.



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2.29.4 All revisions to the Aircraft Flight Manual / Supplement shall be recorded on a Flight Manual Supplement Form (STC Twenty One Ltd Form S21.2.29.REP.018).

2.29.5 The Flight Manual Supplement shall be formatted to allow for STC Twenty One Ltd

approval of minor revisions and for Authority approval for all other revisions. 2.29.6 The Aircraft Make, Model and Serial Number affected by the supplement will be

included within the document. 2.29.7 All Flight Manual Supplements shall have a Contents Page. 2.29.8 All Flight Manual Supplements shall be in the format of the basic aeroplane’s Flight

Manual as far as possible. 2.29.9 The STC Twenty One supplement must detail any other Flight Manual Supplements

that may be affected by the revision. 2.29.10 The completed Flight Manual Supplement will be signed by the relevant

Compliance Verification Engineer(s) in accordance with the Approved Signatory Matrix (See ST21/DOA/HB2, Appendix 2) prior to approval by the Head of Design for minor revisions, or the Authority for all other revisions.

2.29.11 All revisions to the Aircraft Flight Manual / Supplement shall be approved, either

by the Authority, or by STC Twenty One Ltd in the case of minor revisions, and include the following statement:

The technical content of this document is approved under the authority of the DOA ref. UK.21J.0198

2.29.12 Once confirmation of change approval is obtained, the ‘issue’ and ‘approval

record’ of the approved Flight Manual Supplement will be annotated to state clearly the approval of the various issues as per the following example:

2.29.13 The approved Flight Manual Supplement will be issued to the Operator using the

Procedure 2.18.

ISSUE REASON FOR ISSUE/ REISSUE APPROVAL REF.

1 Initial issue As part of STC 10055555

2 MSN XXXX added to effectivity. Under privilege 21.A.263(c)(2) of UK.21J.0198



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2.19 Approved Document Filing Procedure Part 21.A.119, 21.A.265(h)



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2.30 Electrical Load Analysis Report Procedure Purpose: Electrical Load Analysis Reports are used to document the net effect of electrical

loads applied/removed to the aircraft electrical generating/distribution system following the embodiment of a change to inform the Continuing Airworthiness Management Organisation (CAMO) of change to the aircraft Electrical Load data. The Electrical Load Analysis report may also be used to demonstrate compliance with applicable airworthiness requirements affected by the change.

Scope: From the compilation of an Electrical Load analysis to its issue. Definitions: None. Procedure: 2.30.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.30.2 All Electrical Load Analysis Reports shall be recorded on an Electrical Load Analysis

Form (STC Twenty One Ltd Form S21.2.30.REP.019). 2.30.3 The front page of the report shall be signed by the compiler and checked by a

relevant Compliance Verification Engineer in accordance with the Approved Signatory Matrix (See Appendix 2). Approval will be by the Head of Design.

2.30.4 The main body of text is divided into the following headings:

a. Introduction. b. Deleted Equipment. c. Added Equipment.

d. Requirements for Compliance e. Conclusions.

2.30.5 Where an electrical load net effect cannot be calculated due to the absence of a

current ELA, direct measurements may be taken and recorded. In this case, Procedures 2.21 & 2.22 will be used to control and record the observed net effects.

2.30.6 Copies of the Electrical Load Analysis Reports are distributed to the customer,

using Procedure 2.18. 2.30.7 A Technical Report (STC Twenty One Ltd Form S21.2.26.REP.015) may be used to

supplement the ELA report to document loading calculations and/or any additional electrical calculations to determine items such as wire and circuit breaker selection. The Technical Report is intended to contain data which is not required for use outside of STC Twenty One Limited.



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2.30.8 Notwithstanding the above, if the change to the aircraft electrical load is considered to have a negligible effect to aircraft electrical loading, the Accomplishment Instructions and/or Supplemental Manual is an acceptable to medium to provide load change data to the CAMO.

2.30.9 NOTE: Dependent on the certification basis of the design change, the electrical

load change may have to be documented within the Supplemental Manuals to demonstrate compliance.


2.21 Test Plan Procedure 2.22 Test Report Procedure 2.26 Technical Report Procedure 2.47 Supplement Manual Procedure

Part 21.A.265(h)



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2.31 Concession Procedure Purpose: A concession application is made when an authorisation is required to accept an

action that is not in accordance with the relevant drawings or documents that define the design. A concession application must not be used to plan for a deviation to approved design data.

Scope: From the compilation of a Concession form to its issue. Definitions: 27TSADD –27T Statement of Approved Design Data Procedure: 2.31.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.31.2 All Concessions shall be recorded on a Concession Application, form

S21.2.31.REP.020. 2.31.3 If an approval to a concession application requires a rework or other further action,

then this must be described on the Concession response. A service bulletin may be used if necessary (refer to Procedure 2.23). If a separate Repair approval is necessary, refer to Procedure 2.45.

2.31.4 Each concession application shall bear the name of the person requesting the

concession, the responding author and the signature of the relevant Compliance Verification Engineer(s).

2.31.5 The signatory is to ensure that the instructions comply with the Airworthiness

Code declared in the Certification Basis for the change/repair as documented in the Certification Programme and using procedure 2.10, as a guide, to ensure that the rework action does not require re-classification of the change.

2.31.6 The completed Concession Application will be distributed in accordance with

Procedure 2.18. 2.31.7 All Concession requests will be approved by the Head of Office of Airworthiness. 2.31.8 If a concession is granted, it must be recorded on the

Remarks/Conditions/Limitations section of the SADD effective for Change/Repair and or manufacturing/repair drawing to which the concession refers.



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References: 2.10 Change or Repair Classification Procedure 2.15 Minor Change/Repair Approval Procedure

2.16 Certification Programme Procedure 2.18 Document Issue Procedure 2.19 Approved Document Filing Procedure 2.28 Design Office Instruction Procedure. 2.45 Repairs 2.46 Statement of Approved Design Data Procedure

Part 21.A.4, 21.A.33(c), 21.A.109(a), 21.A.118A(a)



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2.32 Design Query Note Procedure Purpose: A Design Query Note (DQN) is generated by any party issued with design data to

gain clarification where the drawing or data appears to be ambiguous or incorrect or if there is a recommendation of improvement to the design or to document a situation whereby the design data cannot be fully embodied.

Scope: From the compilation of a Design Query Note to its issue. 27TDefinitions:27T DQN – Design Query Note 27T SADD –27T Statement of Approved Design Data In-service aircraft (a/c) – an aircraft released to service post embodiment of the

subject design change. Procedure: 2.32.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.32.2 All DQNs shall be recorded on a Design Query Note, form S21.2.32.REP.021. 2.32.3 Once Section A has been completed the DQN will be passed to the design office

for recommended action. 2.32.4 Section B will be completed by STC Twenty One Ltd, or approved design sub-

contractor. 2.32.5 If the DQN relates to an in-service aircraft, then the DQN must NOT provide

corrective actions by STC Twenty One Ltd. This includes agreement to any proposed corrective action contained within Section A. The DQN reply should refer only to the document that will provide the corrective action e.g. Service Bulletin, or a change to the ICA. In such instances, confirm agreed action with HoD/HOOOA (or deputies). An occurrence investigation may need to be raised.

2.32.6 The compiler of Section B should investigate the query, including any impact on

design or certification data and document a reply to the query. 2.32.7 The DQN is passed for checking and approval. The CVE is to ensure that the agreed

actions comply with the Airworthiness Code declared in the Certification Programme. Using procedure 2.10, as a guide, document the classification of the design office reply as either major or minor.



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2.32.8 Once complete the DQN will be passed to the Head of Office of Airworthiness for

review and approval. 2.32.9 With the exception of DQNs raised internally within STC Twenty One Ltd to

document Amendments or Deviations (see 2.10), the completed DQN will be distributed in accordance with Procedure 2.18 and a SADD will be issued.

2.32.10 The agreed/approved course of action may result in a revision to a document e.g.;

a drawing or accomplishment instruction. If this is the case, the affected document will be referenced on the DQN. The DQN may be either incorporated or referenced in the document using the relevant document revision procedure.

2.32.11 If the agreed/approved course of action does not require an amendment to

a document but needs to be retained as part of the approved data package, the DQN must still be listed on the SADD. An example would be a No Technical Objection (NTO) to a requested deviation to a design change instruction that does not require an amendment to design data.

2.32.12 It is not essential to revise a document immediately, but this must be completed

before the job / design change is closed / completed. 2.32.13 If the design change/repair is issued prior to document revision, the DQN(s) must

be listed on the Statement of Approved Design Data. References: 2.7 Occurrence Investigation and Reporting 2.10 Change or Repair Classification Procedure 2.12 Certification Programme, Establish of Certification Basis and

Compliance Checklist Procedure 2.16 Master Document List procedure 2.18 Document Issue Procedure 2.26 Technical Report Procedure 2.30 Electrical Load Analysis Procedure 2.45 Repairs 2.46 Statement of Approved Design Data Procedure Part 21.A.4, 21.A.33(c), 21.A.109(a), 21.A.118A(a)



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2.33 Hazard, Safety, Maintenance Analysis and Continued Airworthiness Procedure

Purpose: This procedure shows how STC Twenty One Limited takes responsibility to identify

and mitigate safety related aspects of design changes to ensure continued airworthiness for the entire life cycle of the design change.

Scope: From the initial compilation of design data, feedback during installation though to

in-service experience and operator feedback. Definitions: Changes – Refers to both Design Changes (major and minor) and

Repairs (major and minor) raised by STC Twenty One Ltd. In-service aircraft (a/c) - an aircraft released to service post embodiment

of the subject design change. Procedure: Hazard Analysis 2.33.1 During the initial compilation of a design project consideration shall be given to

the potential effects of system functional failures resulting from the incorporation of the design change. At the classification stage (see procedure 2.10), the design definition should be sufficiently established to determine whether the design could potentially compromise aircraft safety through identification of hazards including potential functional failures of newly installed equipment, modified equipment or existing aircraft systems via interface with the new design.

2.33.2 System functional failures are classified as Catastrophic, Hazardous, Major, Minor

and No Safety Effect as defined by CS25.1309 and AMC25.1309. Functional failures identified as Catastrophic or Hazardous require design changes to be classified as Major requiring Supplemental Type Certificate (STC) approval.

NOTE: STC Twenty One Limited has not demonstrated competency to mitigate of

functional failures associated with execution of software classified as Major or above (software level C, B or A) and so design changes involving such software

cannot be certified by STC Twenty One Limited.

2.33.3 A preliminary hazard analysis (taking into account all phases of flight) does not need to be in the form as described in SAE ARP 4761 but there should be enough detail in the form of a justification recorded in the classification checklist identifying the worst case functional failure.



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2.33.4 Functional failure classifications identified as Major and above shall be agreed with the Authority during the STC process and will form the basis of certification safety statements and/or analysis.

System Safety Statement and Analysis 2.33.5 Where the preliminary hazard analysis has determined that the equipment failure

classification is Minor or No Safety Effect and that no other airworthiness-related functions are affected, no further safety analysis is required.

2.33.6 Based on the agreed functional failure classifications, a system safety analysis shall

be produced in accordance with DP206 for classifications of Major effects or worse unless otherwise agreed in writing with the Authority (CS25.1309).

2.33.7 The analysis method shall follow either a qualitative assessment and effects

analysis as defined in CS25.1309 section 9, or a quantitative assessment as defined in CS25.1309 section 10. A fault tree analysis shall be produced to support the conclusions.

Maintenance Analysis and Continued Airworthiness 2.33.8 During the design phase the maintenance aspects shall be taken into account in

accordance with CS25.1529. Where a periodic maintenance action is identified to either support a safety statement, analysis or a structural check is to be added to the Maintenance programme (MPD derived programme) a maintenance schedule shall be produced as part of the design package and provided to the customer as per Procedure 2.18.

2.33.9 The effect on any Maintenance Manuals, Crew Manuals, OSD, Electrical Load

Analysis Manuals, or other aircraft document or task as a result of the change will be identified in S21.2.12.REP.005 and supplied to the customer as per Procedure 2.18.

External Feedback (See Figure 1)

2.33.10 Provision is made for external organisations to communicate feedback relating to

changes generated by STC Twenty One Limited either though an arrangement (see procure 2.9) or via feedback sheets on drawings, accomplishment instructions (see procedure 2.34), service bulletins (see procedure 2.23) and supplement manuals (see procedure 2.47).

2.33.11 External feedback on changes can come at any time of the design lifecycle and

normally from one of three sources; Production Organisations (POA), Maintenance



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Organisations (MOA) or aircraft operator Continuing Airworthiness Management Organisations (CAMO).

2.33.12 In the case of a POA, feedback is documented in the form of a Design Query Note

(DQN – see procedure 2.32) or Concession application (See procedure 2.31). 2.33.13 In the case of an MOA, feedback is documented in the form of a DQN, Concession

application or through an Accomplishment Instructions or Service Bulletin feedback sheet.

2.33.14 In the case of a CAMO (or MOA after installation of a change), feedback is

documented through a Supplement Manual feedback sheet. 2.33.15 In addition to the above identified official feedback forms, any other feedback

including email, telephone, fax etc should be addressed as appropriate. 2.33.16 All external feedback shall be reviewed to identify apparent or potential safety

hazards. Where potential safety hazards are identified, procedure 2.7 shall be followed. Where doubt exists consult HoD (or deputies) or HISM.

2.33.17 Where feedback indicates a need for corrective action, the corrective action shall

be applied to the design change in the first instance following procedure 2.10. Once the design has been corrected, retrospective corrective actions shall be communicated to the operator, of in service a/c, via a Service Bulletin.

2.33.18 Where feedback indicates a need for an amendment to the maintenance interval

or design, the proposal may be required to be presented to the Authority for review and comment. Once agreed, the revised Instruction for Continued Airworthiness will be distributed to all owners incorporating the change in accordance with the document issue procedure (See Procedure 2.18).



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References: ST21/DOA/HB1 - 1.7.3.17 2.7 Occurrence Investigation and Reporting

2.10 Change or Repair Classification Procedure 2.18 Document Issue Procedure 2.44 Airworthiness Monitoring Procedure 2.47 Supplement Manual Procedure 2.49 Instructions for Continued Airworthiness Design Procedure DP206

Part 21.A.3A(a)(c)(1), 21.A.4(b), 21.A.109(a), 21.A.118A(a), 21.A.265(c) CAA CS 25.1309, AMC25.1309 SAE ARP 4761



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2.34 Accomplishment Instruction Procedure Purpose: Accomplishment Instructions are generated to give change/repair

accomplishment instructions to organisations embodying the Company’s approved change/repair.

Scope: From the compilation of Accomplishment Instructions to their issue. Definitions: None. Procedure: 2.34.1 Reports to be completed in accordance with procedure 2.0, Report Completion. 2.34.2 All Accomplishment Instructions shall be compiled on form S21.2.34.REP.022. 2.34.3 The first issue of an Accomplishment Instruction will be issue P1 for prototype

design changes. After the design change has been approved the first official issue of an Accomplishment Instruction will be issue 1. Subsequent up-issues will be numbered incrementally e.g. P2, P3 etc for prototype design changes and 2, 3, etc for approved design changes.

2.34.4 The front sheet of the Accomplishment Instructions shall be signed by the

compiler, independent checker(s) and document approver(s). 2.34.5 When the relevant design change/repair is approved, the front sheet shall be

additionally completed to include: (a) the Head of Design signature and date (using the DOA approval number), and (b) the addition of the approval reference.

2.34.6 Accomplishment Instructions for the embodiment of a repair (in cases where a

repair is not already fully documented in either a drawing/drawings or a repair document [Form S21.2.45.REP.001]) will contain cross references to relevant sections of the Aircraft Structural Repair Manual where applicable.

2.34.7 Accomplishment Instructions should consider the following and include further

details, where required: (a) Introduction

(i) Planning Information (ii) Effectivity (iii) Brief Description (iv) Reference Publications Required



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(b) Material Information (i) Re-identified Parts (if any) (ii) Tooling (only if special tooling is required) (c) Accomplishment Instructions 2.34.8 All Accomplishment Instructions shall include an instruction to record the work

accomplished. Examples include but are not limited to: where the Accomplishment Instructions modify a product:

“Record embodiment of STC Twenty One Ltd Change S21.XX-XX-XXXX, in the Aircraft Technical Log or Work Card as appropriate”;

where the Accomplishment Instructions create (or modify) a part for later

installation in a product: “Part mark [or Re-part mark] in accordance with Part 21.A.804 using [method, e.g. indelible ink] with (a) Manufacturer’s identification, (b) part number XXXXX, and (c) the letters UKPA, at [define location for part mark, e.g. adjacent to existing].

References: 2.18 Document Issue Procedure 2.39 Drawing Issue Procedure 2.45 Repairs

Part 21.A.265(h), 21.A.443



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2.35 Reserved



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2.36 Reserved



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2.37 Company Design Procedures Purpose: The purpose of this procedure is to define the use of supporting processes and

procedures followed in support of the Company’s DOA activities. Scope: To define acceptable Design procedures to be followed by all design office staff. Definitions: Company Design Procedures: Company Procedures are documents containing

guidance and detailed instructions for staff to enable them to implement the instructions contained in the Company Handbooks.

Procedure: 2.37.1 All Company Design Procedures are contained in STC Twenty One Ltd Design

Manual ST21/DOA/HB3 2.37.2 The Design procedures manual is subject to its own amendment procedure and

approval of the manual and each revision are carried out under the authority of the Head of Design.

References: STC Twenty One Ltd Design Manual ST21/DOA/HB3



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2.38 Drawing Compilation Procedure Purpose: To define the procedure for compiling drawings. Scope: From the compilation of a Drawing to its issue. Definitions: None. Procedure: 2.38.1 Each drawing has a unique identification number. These numbers are constructed

as follows:

xx - xx - 1xxxx ATA Chapter Aircraft type ident. Sequential number e.g. 25-13-10001

2.38.2 The ATA Chapter reference and the Aircraft type identification number are

obtained from the Drawing Register database. 2.38.3 The 5-digit sequential number is also obtained from the Drawing Register

database, held in the Design Office.

2.38.4 Drawings are generated to standards contained in the Company Design Manual, ST21/DOA/HB3.

2.38.5 The revision levels of “Prototype” drawings associated with unapproved design

changes/repairs are generated under an alpha-numerical issue ref P1, P2, P3 etc. The first issue of a prototype drawing will be P1, subsequent amendments will be recorded as issue P2, P3 etc.

NOTE: The signed “Approved” box on a prototype drawing indicates that the

drawing has been internally checked and approved for release to the installer or manufacturer. This does not constitute or infer design approval and prototype drawings are not “approved data”.

2.38.6 The revision levels of drawings associated with approved data are generated under

an alpha issue ref A, B, C etc. The first approved issue will be A, subsequent amendments will be recorded as issue B, C etc.

2.38.7 Parts (design change & repair) manufactured or modified must be part marked in

accordance with the STC Twenty One Ltd Design Manual and Part 21.A.804. For parts produced in accordance with approved design data, not belonging to the



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type certificate holder of the related product the letters “UKPA” must be used, except for TSO articles. In the case that a part or appliance is too small, or otherwise impractical to apply an UKPA mark and trademark e.g. single electrical wires then a statement containing the words “Part Number XXXX cannot be UKPA part marked. Please record on Form 1 Block 13” should be made on the “Remarks/Conditions/Limitations” section on the Statement of Approved Design.

2.38.8 Where a part has been identified as a critical part it shall be marked in accordance

with Part 21 21.A.805. 2.38.9 Completed drawings are independently checked within the Design Office. 2.38.10 Personnel responsible for the checking and approval of the prototype drawings or

revised prototype drawings will log onto the STC Twenty One Ltd database with their unique username and password. The personnel responsible will check and approve the applicable prototype drawing within the database.

2.38.11 Personnel responsible for the checking and approval of approved or revised

approved drawings will log onto the STC Twenty One Ltd database with their unique username and password. The personnel responsible will check and approve the applicable drawing within the database.

NOTE: Only approved personnel (see procedure 2.5) are able to select the check /

approve function on the database. The database will record who has checked and approved each drawing.

2.38.12 Drawings are issued using the drawing issue procedure (See Procedure 2.39).

References: 2.5 Checker & CVE Selection Procedure 2.39 Drawing Issue Procedure 2.40 Drawing Filing and Retention Procedure. Design Manual ST21/DOA/HB3

Part 21.A.109(b), 21.A.118A(b), 21.A.451(a)2(b)2, 21.A.804, 21.A.805.



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2.39 Drawing Issue Procedure Purpose: To control the issue of approved and prototype mechanical and electrical drawings Scope: From identifying the need to issue a drawing, through its copying to its issue. Definitions: None. Procedure: 2.39.1 All drawings are issued through the Design Office.

2.39.2 The Head of Design will establish the distribution requirements for the drawing

copies.

2.39.3 Prototype drawings will be issued at a ‘P’ level, indicating they are not yet approved data.

2.39.4 When the drawing is approved, it will be annotated with the latest Issue state. For fully approved documents it must be established that the drawing has been checked and is approved by the relevant Design Engineer.

2.39.5 For manufacturing drawings, a Statement of Approved Design Data (SADD) will be issued in accordance with procedure 2.46.

2.39.6 The drawings will be issued via electronic transfer and a record kept in the design office.

2.39.7 The drawing originals will be filed in accordance with the drawing filing procedure (See Procedure 2.40).

References: 2.40 Drawing Filing & Retention Procedure. Design Manual ST21/DOA/HB3

Part 21.A.33(b), 21.A.443.



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2.40 Drawing Filing and Retention Procedure Purpose: To control the filing and retention of approved and unapproved drawings. Scope: From the issue of a drawing to its filing. Definitions: None. Procedure: 2.40.1 Digitally produced drawings are filed and stored on the Design Office server. The

server is backed up via a cloud based service..

2.40.2 Reserved.

2.40.3 Original drawings (historical (AED) “film” drawings) shall only leave the Design Office archive storage for multiple printing. Original drawings shall be listed by those removing them and shall be returned as soon as possible.

2.40.4 All original hard copy drawings are stored at an off-site archive storage facility in a metal cabinet filing system. Access to these drawings is readily available to provide the information necessary to ensure continued airworthiness of the product or change.

2.40.5 All drawings will be retained for as long as the product remains in service and until such time after as may be agreed with the Authority.

References: Part 21.A.105, 21.A.109(a), 21.A.118A(a), 21.A.447, 21.A.451(b)(1)



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2.41 Reserved



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2.42 Reserved



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2.43 Operational Suitability Data (OSD) Supplement Procedure

Purpose: To detail the procedure for the classification, creation and approval of an OSD

supplement. Scope: From the compilation of an OSD supplement, consisting of either a Master

Minimum Equipment List (MMEL), Cabin Crew Data (CCD) or Maintenance Certifying Staff Data (MCSD) to its issue.

27TDefinitions:27T Operational Suitability Data (OSD) – The following data can be classed as OSD:

a. The minimum syllabus of pilot type rating training, including determination of type rating.

b. The definition of scope of the aircraft validation source data to support the objective qualification of simulator(s) associated to the pilot type rating training or provisional data to support their interim qualification.

c. The minimum syllabus of maintenance certifying staff type rating, including determination of type rating.

d. Determination of type or variant for cabin crew and type specific data for cabin crew.

e. The master minimum equipment list. f. Other type-related operational suitability elements.

27TMinimum Equipment List - The MEL is a dispatch document developed by the Operator based on the approved MMEL. The MEL must be as restrictive as or more restrictive than the MMEL and must be approved by the Operator’s national airworthiness authority. The MEL permits the Operator to assess the impact on their operations (flight schedule, route, environmental conditions...) while operating an aircraft with systems, functions or components inoperative, thus, to optimise aircraft dispatch reliability and profitability without impairing safety. Master Minimum Equipment List (MMEL) – 27The MMEL is a dispatch document that is produced by STC Twenty One Limited and approved by the Authority. The MMEL is used as a reference by the Operators to create their own MEL, which will permit the dispatch and operation of an aircraft with one or more inoperative equipment or unavailable system function while maintaining an acceptable level of safety.

Cabin Crew Data (CCD) – Type specific data for cabin crew training. Applicable

when operation rules require cabin crew for the maximum approved passenger seating capacity (currently more than 19 passengers).



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Maintenance Certifying Staff Data (MCSD) – Data used by certifying staff to carry out maintenance on the specific aircraft type.

Procedure: OSD Preparation 2.43.1 Changes, or potential impact to, OSD may be outside of STC Twenty One Ltd terms

of approval. Therefore, this procedure must be reviewed and followed when there is the potential OSD could be affected.

2.43.2 Changes to OSD can be classified as either minor or major. This will be done in accordance with procedure 2.10 and this procedure.

2.43.3 STC Twenty One Ltd is approved to make classifications and approve minor changes affecting the following operational suitability data:

1. The Master Minimum Equipment Lists. 2. Cabin Crew Data. 3. Maintenance Certifying Staff Data.

Note: Any changes (minor or major) to MCSD must be authorised by the Authority prior to STC Twenty One Ltd classification endorsement.

2.43.4 Any change to other OSD cannot be approved by STC Twenty One Ltd without an

update to the procedures and terms of approval.

2.43.5 Where OSD has been classified as major, the overall classification of a change will be major.

2.43.6 For a major change to OSD, an application must be made to the Authority for approval.

2.43.7 Where OSD is affected, STC Twenty One Ltd need to further identify the individual

constituents. Refer to individual sections below for further details.



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MMEL Process NOTE: This procedure has been based on the requirements of CS-MMEL, however the

individual OSD certification basis should be used, and differences followed where appropriate.

2.43.8 All MMEL Supplements shall be recorded on STC Twenty One Ltd Form

S21.2.43.REP.027. The supplement will be numbered using S21.MMEL- followed by a sequential number, allocated using the database.

2.43.9 The Change to the MMEL must first be classified, in accordance with the criteria of 21.A.91, and the appropriate section of GM 21.A.91. Refer to Procedure 2.10 for details of how to conduct the Classification Process.

NOTE: The following guidance is provided for the author and is taken from

GM 21.A.91, paragraph 3.5.

Figure 2 - MMEL Appreciable Items



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Figure 3 - MMEL Non-Appreciable Items

2.43.10 The next step is to analyse each potential MMEL alleviation condition, per the below. The level of safety and the justification of MMEL items must be considered and documented for each item being addressed in the MMEL. The following factors should be considered when preparing MMEL items to ensure the level of safety intended by the requirements is maintained:

(i) reduction of aircraft functional capabilities and/or safety margins; (ii) change in crew workload and/or degradation in crew efficiency; (iii) consequence(s) to the aircraft and its occupants of the next failure(s) having

the worst safety-related impact on the aircraft’s take-off, continued flight and landing when dispatching in a known degraded configuration;

(iv) consequence(s) to the aircraft and its occupants of the next external event(s) for which the item was designed to protect against, if applicable.



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2.43.11 Justification will be provided for each MMEL item. The analysis will be documented in a Technical Report and will be performed in accordance with Procedure DP206. The method selected will be dependent upon the classification of the failure conditions per 2X.1309 One or more of the following methods will be used, as necessary: (i) Qualitative safety assessment which will;

(1) evaluate the consequences of the proposed MMEL dispatch

configuration on the aircraft functional capabilities, crew workload and discomfort to occupants and show compliance with applicable certification basis (e.g. CS MMEL.140);

(2) evaluate the consequences of the next worst safety-related failure and, if applicable for the item, separately evaluate the consequences of the external event for which the item was designed to protect against, and ensure the combination of the MMEL dispatch configuration with the next worst safety-related failure or event do not correspond to an hazardous or catastrophic failure condition; and

(3) notwithstanding paragraph (2) above, specific cases may be accepted when supported by quantitative safety assessment as per paragraph (ii) below.

(ii) The qualitative safety assessment is supplemented by a quantitative safety assessment when both of the following considerations are met: (1) relief is proposed for items, functions and/or systems involved in

catastrophic or hazardous failure conditions, and the severity of the failure condition under MMEL configuration is not mitigated by special operating conditions, limitations or procedures; and

(2) when the operation with the inoperative item leaves the aircraft one failure away from a hazardous failure condition, or one or two failures away from a catastrophic failure condition.

NOTE: Refer to GM1 & GM2 MMEL.140 and GM1 & GM2 MMEL.145 and the Guidance book contained in Appendix 1 to GM1 MMEL.145 for further guidance.



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2.43.12 Upon completion and successful independent verification of the System Safety Assessment, the MMEL itself may be authored in accordance with the guidance of Table 1 - MMEL Form Guidance.

2.43.13 In addition to the above, the following information must be added to the MMEL

form: Definitions: The MMEL should contain sufficient definitions and explanatory

notes to provide the user (this is primarily the operator when compiling the MEL) with a full and proper understanding of the intent and purpose of the items it contains.

Preamble: A standard preamble has been added to the form per CS

MMEL.120. The preamble must be reviewed on a case by case basis and be edited if necessary, for the specific project. As a minimum, the Aircraft Make and Model and the Change Number must be added to the preamble.

2.43.14 Non-safety-related items need not be included in the MMEL, unless so desired by

the applicant. In such circumstances, the process described by this procedure still applies.

NOTE: Non-safety related items include those items related to the

convenience, comfort, or entertainment of the passengers and equipment that is used only on ground for maintenance purpose. This may include items such as galley equipment, movie equipment, stereo equipment, overhead reading lamps. Additional guidance is provided in GM1 ORO.OPS.MLR.105(a).



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Table 1 - MMEL Form Guidance

MASTER MINIMUM EQUIPMENT LIST

AIRCRAFT: Insert Aircraft Make and Model REVISION NO. Insert Here DATE: Insert Here

PAGE: Insert Here

(1) System and Sequence Numbers

IITEM (2) Rectification Interval

(3) Number installed

(4) Number Required for Dispatch

(5) Remarks or Exceptions

(1) The ATA number and System Name should be prescribed in (1)

(2) Inoperative items or components, deferred in accordance with the MEL, must be rectified at or prior to the rectification intervals established by the following letter designators, which should be added to (2). The specified rectification interval must be derived through the Safety Assessment process. Category A No standard interval is specified. However, items in this category shall be rectified in accordance with the conditions stated in the MMEL. (i) Where a time period is specified in calendar days or flight days, the interval excludes the day of discovery. (ii) Where a time period is specified other than in calendar days or flight days, it shall start at the point when the defect is deferred in accordance with the operator’s approved MEL. Category B Items in this category shall be rectified within three (3) calendar days, excluding the day of discovery. Category C Items in this category shall be rectified within ten (10) calendar days, excluding the day of discovery. Category D Items in this category shall be rectified within one hundred and twenty (120) calendar days, excluding the day of discovery.

(3) This represents the number (quantity) of items installed in the aircraft. This number. Must represent the aircraft configuration considered when developing the MMEL and the associated safety assessment. Should the number be variable (i.e. passenger cabin items), or not applicable, a number is not required and a “-“ is to be inserted.

(4) This represents the actual number (quantity) of items required for dispatch of the aircraft, provided the conditions specified are met. Should the number be a variable, or not applicable, a “-“is to be inserted.

(5) include statements either prohibiting or allowing operation with a specific number of items inoperative, provisos (conditions and limitations), notes, (M) and/or (O) symbols, as appropriate for such operation. (M) indicates a requirement for a specific maintenance procedure which must be accomplished prior to operation with the listed item inoperative. Normally these procedures are accomplished by maintenance personnel, however other personnel may be qualified and authorised to perform certain functions. The satisfactory accomplishment of all maintenance procedures, regardless of who performs them, is the responsibility of the operator. (O) indicates a requirement for a specific operational procedure which must be accomplished in planning for and/or operating with the listed item inoperative. Typically, these procedures are accomplished by flight crew.



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MEL NOTES

The following is provided as Guidance Material for the compiler. An MEL falls outside of the DOA scope and is not part of a “Change”.

As per the Definitions at the beginning of this Procedure, the MEL is a document prepared by the Operator and is not a certification document prepared by STC Twenty One Limited in support of a Change to Type Design.

However, it may be that an operator wishes for STC Twenty One Limited to produce an MEL Supplement on their behalf. In this case, the following applies:

• The MEL MUST fall outside of the approved Change and must not be referenced anywhere

in the certification package, • The MMEL Form (S21.2.43.REP.027) MUST NOT be used as this contains the statement

obligated by 21.A.265(h) which CANNOT be used in this instance. In addition, a CVE check CANNOT be applied to a document falling outside of a Change. The MMEL Form may be used to produce an MEL template, however guidance must be sought from the HOOOA and/or HDO before continuing.

• The MMEL must be reviewed prior to compiling an MEL, as the MEL MUST BE as restrictive, or more so, than the MMEL,

• The MEL MUST BE approved by the Operator and their National Airworthiness Authority. STC Twenty One Limited CANNOT approve an MEL.



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CCD Process

Figure 2 - CCD Classification

OSD change related to change to the type design. 2.43.15 When classifying the OSD CCD change as minor or major, the method from CS-CCD,

Subpart B should be used. (i) An analysis should be performed to assess the change impact on the OSD

CCD through the identification of the difference and its impact on operation in the aircraft difference table (ADT) as per CS CCD.200. In this case, the base



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aircraft is the aircraft without the type design change, whereas the candidate aircraft is the aircraft which includes the type design change.

(A) If the difference has no impact on the operation of an element of the ADT

for the candidate aircraft, the related OSD CCD change should be classified as minor.

(B) If the difference has an impact on the operation of an element of the ADT

for the candidate aircraft, the related OSD CCD change should be classified as major.

(ii) Notwithstanding the above, the change to OSD CCD should be classified as

major when an ADT analysis is found necessary by the applicant to confirm that the aircraft with the type design change is not a new type for cabin crew.

2.43.16 Stand-alone changes to OSD CCD are not related to any type design changes. They

may be triggered for example by in-service experience or by the introduction of data at the request of the applicant after type certification.

(i) Stand-alone changes to cabin aspects of special emphasis (CASE) should be

classified as major. Example: addition of further CASE, expansion of CASE. (ii) When classifying stand-alone changes to type-specific data for cabin crew

the method from CS-CCD, Subpart B should be used. An analysis should be performed to assess the change impact on the type-specific data through the identification of the difference and its impact on operation in the ADT as per CS CCD.200.

(A) If the change does not concern a determination element of CS CCD.205,

the stand-alone change should be classified as minor. (B) If the change has no impact on the operation of an element of the ADT,

the stand-alone change should be classified as minor. (C) If the change has an impact on the operation of an element of the ADT,

the stand-alone change should be classified as major. 2.43.17 CS-CCD should be used in the completion of all CCD.

2.43.18 CCD is applicable to;

a. aircraft with a passenger seating capacity of more than 19 seats; b. aircraft with a passenger seating capacity of 19 seats or less required to carry

cabin crew; and



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c. any other aircraft with a passenger seating capacity of 19 seats or less if voluntarily elected by the applicant.

2.43.19 The CCD classification process and completion of the Aircraft Differences Table

(ADT) will identify whether there is a new type or variant for cabin crew and also any type specific data required for cabin crew.

2.43.20 Changes including, but not limited to, the following areas could affect cabin crew operations and therefore CCD. Refer to CS-CCD ADT for full details:

a. Aircraft configuration change b. Changes to doors and exits c. Aircraft systems affecting but not limited to

(i) Emergency lighting (ii) Evacuation alarm signal (iii) Smoke detection (iv) Automatic fire extinguishing system (v) Drop down oxygen system (vi) Communication system (vii) Public address system (viii) Control panels (ix) Water system

d. Normal and emergency operations

2.43.21 All CCD Supplements shall be recorded on STC Twenty One Ltd Form S21.2.43.REP.028.

2.43.22 The front page shall bear the Aircraft Make and Model affected by the supplement.

2.43.23 All CCD Supplements should contain, cover page, revision history, detailed

summary of changes at last revision, list of effective pages and a table of contents.

2.43.24 Data should be clearly marked and segregated into sections marked Mandatory and Non-mandatory (recommendations).

MCSD Process 2.43.25 MCSD supplements may be required if there is an introduction of a new type of

task that is not currently part of the current aircraft MCSD. 2.43.26 The Authority should be contacted to ensure that any affected MCSD is within STC

Twenty One Ltd scope of work, and to classify MCSD change. After discussions with the CAA, MCSD is to be compiled following where possible the TC holders MCSD layout.



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Approval and issue of OSD 2.43.27 The completed OSD supplement will be signed by the relevant Compliance

Verification Engineer in accordance with the Approved Signatory Matrix (see appendix 2) and then for major changes submitted to the Authority for approval.

2.43.28 For major changes to OSD, once confirmation of Authority approval is obtained, the approved OSD supplement front page will be annotated accordingly.

2.43.29 Minor changes to OSD will be approved by the HoD (or deputies) on the OSD supplement front page.

2.43.30 The approved OSD supplement will be issued to the operator in accordance with procedure 2.18.

2.43.31 Amendments are to be made in accordance with this procedure and identified in the amendment record. The OSD supplement issue is to be raised to the next issue and for major amendments, approved by the Authority.

References: 2.10 Change or Repair Classification Procedure 2.18 Document Issue Procedure 2.26 Technical Report Procedure 2.45 Repairs Part 21.A.91, 21.A.101, 21.A.108, 21.A.109(a), 21.A.118A(a), 21.A.119, 21.A.120B. CS-MMEL, CS-GEN-MMEL, CS-CCD CAA OSD application Form SRG1726NR



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2.44 Airworthiness Monitoring Procedure Purpose: To ensure that any occurrences/incidents that may have an adverse effect on the

airworthiness of any company promulgated changes/repairs are monitored. Scope: From monitoring published data to instigation of corrective action when

applicable. Definitions: None. Procedure: 2.44.1 The Office of Airworthiness will be responsible for, on a weekly basis, monitoring

CAA, EASA and FAA web sites, including bi-weekly listing, for any incident/occurrence that may have an adverse effect on the continuing airworthiness of a company product.

2.44.2 Any incident/occurrence which may have an impact on a Company product is to

be notified to the office of airworthiness. 2.44.3 Where there is a resulting effect on a Company change/repair of such significance

that immediate remedial action is to be taken, it is to be reported in accordance with procedure 2.7 within 72 hours.

References: Part 21.A.3A(a)



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2.45 Repairs Purpose: To determine how STC Twenty One Limited classifies, evaluates and approves

damage and repairs. Scope: To provide guidance for the assessment of damage; to the evaluation and

subsequent approval of unrepaired damage or repair. Definitions: Repair – Elimination of damage and/or restoration to an airworthy condition. Unrepaired Damage – Damage that will not be repaired, addressing specific areas

not covered by previously approved data as defined by the approval holder. Procedure: 2.45.1 Damage to a product, part, or appliance, may either be considered to be left in an

unrepaired state or can be repaired. STC Twenty One Ltd will evaluate the airworthiness consequences and determine which is required.

2.45.2 Repairs and evaluations of unrepaired damage will be recorded in an STC Twenty

One Ltd Repair Document (S21.2.45.REP.001). 2.45.3 All damage and subsequent repair assessments are subject to classification using

guidance detailed in Procedure 2.10, however the classification will be recorded in an STC Twenty One Ltd Repair Document.

2.45.4 The Classification Checklist is included in the Repair Document. The intent of

Procedure 2.10 must be considered and followed whilst compiling the Repair Document. If a change to a Flight Manual is required, this shall be classified using a FAC (STC Twenty One Ltd Form S21.2.29.REP.036).

2.45.5 The Repair Document will include the minimum descriptive information normally

documented in procedure 2.12, Certification Programme, Establishment of Certification Basis and Compliance Checklist.

2.45.6 For all major repairs, the Repair Document will include within the certification and

compliance information the derivation of compliance demonstration items and associated information required for Level of Involvement (LOI) in procedure 2.12, Certification Programme, Establishment of Certification Basis and Compliance Checklist.

2.45.7 For repairs approved by the Authority , the Level of Involvement must be agreed

by the Authority.



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2.45.8 The Repair Document will include a Master Document List in lieu of a separate MDL

document. 2.45.9 All unrepaired damage and repair assessments will be included in the Repair

Document and a Technical Report (TREP) if required. The assessment will include all necessary instructions and limitations that will be issued to the operator within the Repair Document, S21.2.45.REP.001.

2.45.10 Temporary repairs: It is permissible to issue a repair approval for a limited time to

permit subsequent repair. In this case a limitation must be clearly stated within the Repair Document.

2.45.11 Fatigue and damage tolerance: It is permissible to issue a repair approval for a

limited time to permit fatigue/damage tolerance analysis to be performed. In this case a limitation must be clearly stated within the Repair Document to state when the damage tolerance data will be completed. This may be no later than 12 months from initial release to service (Refer to Annex 1 to Appendix 3 to AMC 20-20).

2.45.12 The assessment of unrepaired damage and repairs will be made considering the

scope of STC Twenty One Ltd approval and experience of the aircraft type or appliance. Any information, guidance or communication sought from the TC or STC holder shall be documented and included as part of the Repair Document. These assessments are to be recorded in the Approval Basis section of the Repair Document, which will also state the approval basis as below (2.45.16 through 2.45.18).

2.45.13 A repair to an ETSO article, other than an APU, installed on an aircraft may be

considered as a repair to the product in which the article is installed, not to the article taken in isolation. GM 21.A.431(d) provides further information. To ensure configuration control is maintained by the installer/operator, a statement to this effect must be made in the conditions and limitations section in the Repair Document and SADD.

2.45.14 A declaration of compliance and approval of the repair will be documented in the

Repair Document but will follow the intent of procedure 2.15 and 2.17. 2.45.15 Despite the apparent contradiction, unrepaired damage is approved as a repair

and this will be via the Repair Document approval. 2.45.16 Minor repairs will be approved under STC Twenty One Ltd privilege 21.A.263(c)2.



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2.45.17 Major repairs to an STC Twenty One Ltd STC may be approved under STC Twenty One Ltd privilege 21.A.263(c)5. If there is any doubt the Authority must be contacted.

2.45.18 Major repairs to a product, part or appliance that are not covered by an STC

Twenty One Ltd STC, will be approved by the Authority under a Major Repair Approval. Refer to Procedure 2.17 for the application and approval process.

References: 2.10 Change or Repair Classification Procedure

2.12 Certification Programme, Establish of Certification Basis and Compliance Checklist

2.18 Document Issue Procedure 2.26 Technical Report Procedure 2.29 Flight Manual Supplement Procedure 2.46 Statement of Approved Design Data Procedure Part 21.A.20(d), 21.A.263(c)2,5, 21.A.431A(c)(d)(e)(f), 21.A.432C, 21.A.433,

21.A.435, 21.A.443, 21.A.445, 21.A.449, 21.A.451(a)(1)(b)(1)



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2.46 Statement of Approved Design Data Procedure Purpose: To clearly define the use, and issue of, a Statement of Approved Design Data

(SADD). Scope: From the creation, issue and filing of a SADD. Definitions: Prototype Data – Drawings/reports that have not yet been approved by a

completed design change. Approved Design Data – Drawings/reports approved by the Authority or STC

Twenty One Limited under its DOA approval. Procedure: 2.46.1 A Statement of Approved Design Data is issued by STC Twenty One Limited on

Form S21.2.46.REP.035 to show that the design data being released is either prototype, approved by a minor change or approved by an STC.

2.46.2 A SADD may be issued under the following circumstances:

a) The data is classed as prototype when the design change has yet to be approved.

b) When the design change or repair is approved by either:

i) STC Twenty One Limited – Design changes/repairs classified as minor (See procedure 2.15)

ii) STC Twenty One Limited – Repairs classified as major to an STC Twenty One Ltd STC (See procedures 2.17 and 2.45)

iii) The Authority (CAA) – Design changes/repairs classified as major

(See procedure 2.17) 2.46.3 A SADD is released by STC Twenty One Limited:

a. To permit an appropriately authorised Part 21 approved Production Organisation (POA) to manufacture a part or parts in accordance with an STC Twenty One Limited drawing. (See procedure 2.9).

b. To permit an organisation to carry out test(s) to a part or material in accordance with a drawing or test plan.



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c. To permit the embodiment of an approved STC Twenty One Limited design change/repair by an appropriately authorised Part 145 approved Maintenance Organisation (MOA).

d.

2.46.4 Prototype data is only issued with a SADD for the purpose of testing or to permit manufacture by an approved Production Organisation (POA).

2.46.5 A SADD will identify the following: -

a. The design change / repair number. b. A unique identifier, numbered sequentially, and supplemented by an ‘M’

for SADDs issued for manufacture and ‘T’ for SADDs issued for testing (e.g 1, 2, 3M, 4, 5T, 6).

c. Whether the data is associated with a change or repair. d. The aircraft type or part number as applicable. e. The eligibility of the design data by aircraft or part serial number

effectivity. f. The type of data e.g. Drawing, Report, Change/Repair. g. The identification of the data e.g. drawing or report number(s). h. The Master Document List (MDL) or Repair Document reference (See

procedures 2.16 and 2.45). (optional for SADDs issued for manufacture). i. The purpose of the data (Refer to 2.46.6). The DOA-POA Arrangement

number must be listed for SADDs issued to a POA for manufacture. j. Any remarks/conditions or additional limitations affecting the design

change/repair as identified S21.2.12.REP.005 that are not listed in the following S21.2.34.REP.022 (ACC), S21.2.29.REP.018 (FMS) and S21.2.47.REP.043 (AMMS including MPDS) will be listed.

k. If issued, a reference to any Concession Application(s) or Design Query Note(s) not embodied into a document relating to a design change/repair or manufactured part (See procedures 2.31 and 2.32).

l. Declaration that the data is either approved under 21.A.263(c)2, approved by the Authority, or is prototype and not yet approved.

m. Head of Design approval signature.

2.46.6 A new SADD will be issued if the eligibility is changed. 2.46.7 The SADD electronic file is named as the design change followed by the unique

identifier, e.g. S21.25-13-1234_2M for design changes, or as S21.SADD-REP-XXXX_2M for repairs, and is filed in the applicable design change/repair folder (See procedure 2.11).



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References: 2.9 Liaison Between STC Twenty One Ltd and the Selected Contractor 2.10 Change or Repair Classification Procedure

2.11 Civil Change/Repair Record Procedure 2.15 Minor Change/Repair Approval Procedure 2.16 Master Document List Procedure 2.17 Major Change/Repair Approval Procedure 2.18 Document Issue Procedure 2.39 Drawing Issue Procedure 2.45 Repairs Part 21.A.4, 21.A.31, 21.A.33(b), 21.A.109(a), 21.A.118A(a), 21.A.443,

21.A.451(a)1(b)1.



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2.47 Supplement Manual Procedure Purpose: To clearly define the definition of a Supplement Manual, its preparation and issue. Scope: From the creation to the issue of a Supplement Manual. Definitions:

27TATA – Air Transport Association standardised chaptering (ATA 100) AWL / ALI– Airworthiness Limitations ICA – Instructions for Continued Airworthiness LRU – Line Replicable Unit Supplement Manual Types: AMMS – Aircraft Maintenance Manual Supplement, includes the

MPDS and ALI sections IPCS – Illustrated Parts Catalogue Supplement MPDS – Maintenance Planning Document Supplement TEC – Other Supplement Manual not specifically covered elsewhere WDMS – Wiring Diagram Manual Supplement Procedure: 2.47.1 At revision 18 of this handbook, the supplement manual and procedure were

extensively changed. Supplement Manuals issued prior to revision 18, can remain on a S21.TEC-XXXX. If there are extensive changes needed to be made to S21.TEC-XXXX then HoD (or deputies) will determine if this manual is to be transposed into the new format (AMMS/IPC/WDMS).

2.47.2 A Supplement Manual will be numbered using either S21.AMMS-XXXX, S21.IPCS-

XXXX, S21.WDMS-XXXX or S21.TEC-XXXX. A 4 digit sequential number will be allocated by the database and a register will be kept on the database.

2.47.3 Each page of the Supplement Manual shall be identified with the supplement

manual number, section and page number, aircraft effectivity and the date of issue. Except the title page which will not include aircraft effectivity or section and page number.

2.47.4 The following will be included in the front matter of the supplements:

a. Transmittal Notice information b. Maintenance Reporting Form



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c. Approval sheet d. Revision record e. Table of contents for the whole supplement

2.47.5 2.47.5 For supplements that use ATA chapters (such as AMMS, IPCS, WDMS), chapter 00 will include the following as a minimum:

a. Purpose of the supplement, including specifics on its use. b. Applicability, details of the aircraft effectivities. c. STC Twenty One Limited contact details. d. Definitions and Abbreviations. e. Any other details that will assist the reader in the use of the manual,

such as descriptions of part numbers, how to read tables.

2.47.6 Each approved Supplement Manual shall contain a transmittal notice instructing the recipient to file the supplied Supplement Manual together with the affected manual(s) IAW the operator’s approved procedures for technical publication filing and retention.

2.47.7 Each approved Supplement Manual shall contain a feedback statement to enable

the operator to contact STC Twenty One Limited if there are any findings during maintenance that are considered to affect continued airworthiness. Refer to procedure 2.33.3(c).

2.47.8 Each approved Supplement Manual shall be produced in electronic format,

suitably indexed, and issued to the customer. Reference procedure 2.18. 2.47.9 A PDF copy of each Supplement Manual shall be kept.

Aircraft Maintenance Manual Supplement (AMMS) - ICA 2.47.10 The AMMS details the way in which all maintenance tasks carried out shall be

accomplished. This includes items such as lubrication, system functional checks and servicing, but usually excludes structural repairs and modifications. The AMMS is classed as the ICA.

2.47.11 Where a design change includes multiple ATA chapters the information must be

allocated into the correct chapter. These headings will be repeated as necessary in each ATA style chapter.

2.47.12 The approval sheet of the ICA shall be formatted to allow for STC Twenty One Ltd

approval & CVE Signature. 2.47.13 All AMMS shall contain the following sections of main text, included as

appropriate:



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SECTION TITLE PAGE RANGE Description, Operation and Location 1-99 Troubleshooting 101-199 Maintenance Practices 201-299 Servicing 301-399 Removal / Installation 401-499 Adjustment / Test 501-599 Inspection Check 601-699 Cleaning / Painting 701-799 Repairs 801-899 Maintenance Procedures 901-999

2.47.14 The AMMS should give suitable instructions, illustrated where possible, to

maintain an installed design change. It should provide instructions, when viable, for the installation, removal and testing of all items, including LRU’s (Line Replaceable Units) and associated installation hardware.

2.47.15 The AMMS will include an ALI section. The following statement will be added,

regardless of whether ALIs are affected or introduced as part of the design change: The Airworthiness Limitations section is approved and variations must also be

approved. 2.47.16 If ALIs are introduced, they will be included within the MPDS section. 2.47.17 The MPDS section, if required, is contained as an appendix to the AMMS it will

contain the maintenance requirements/tasks that need to be carried out on an aircraft in order to ensure its continuing airworthiness.

Illustrated Parts Catalogue Supplement (IPCS) 2.47.18 A key ancillary reference document specific to aircraft type which describes in

comprehensive detail every component. It is an essential supplement for users of the AMMS but does not have the equivalent approved status and must be used only as supporting reference with the AMMS as authoritative reference in case of any differences.

2.47.19 The IPCS will list the LRU’s with installation equipment and items installed by a

design change. It will be broken into ATA 100 style chapters to support the maintenance of an installed design change. Where a design change includes multiple ATA 100 chapters the diagrams must be allocated into their correct chapter.

https://www.skybrary.aero/index.php/Continuing_Airworthiness

https://www.skybrary.aero/index.php/AMM

https://www.skybrary.aero/index.php/AMM



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2.47.20 Items will be listed in table form showing the given part number, quantity,

description and effected aircraft. 2.47.21 Where possible illustrations will be included to identify the location of the installed

part(s) and the construction/interaction of the installed part(s). Wiring Diagram Manual Supplement (WDMS) 2.47.22 The WDMS provides a physical view of systems, sub/systems and reflects the

definition of the wiring installation allowing for understanding of the electrical, electronic, electro-mechanical systems and physical connections.

2.47.23 The WDMS will be broken into ATA 100 style chapters including the post

installation wiring diagrams to support the maintenance of an installed design change. Where a design change includes multiple ATA 100 chapters the diagrams must be allocated into their correct chapter.

2.47.24 Electrical wiring connections, components and other items not appearing in the

basic WDM should be included in ATA Chapter 20, to provide the necessary maintenance information.

TEC 2.47.25 For Supplement Manuals not specifically listed above, S21.TEC-XXX will be used.

Examples of times a TEC manual may be considered are: CMM updates, times where the data supplied is not suited to being placed into separate AMMS, IPCS & WDMS manuals & FCOMS. Note this is not an exhaustive list, and it is at the discretion of the HoD or HOOOA (or deputies) if a TEC manual may be used.

2.47.26 Where applicable it will be broken into ATA 100 style chapters to support the

maintenance of an installed design change. Where a design change includes multiple ATA 100 chapters the diagrams must be allocated into their correct chapter.

2.47.27 It will be determined by the HoD or HOOOA (or deputies), what sign off is required

for the type of TEC manual being raised. 2.47.28 An example of the TEC Manual is for a Flight Crew Operating Manual Supplement

(FCOMS). An FCOMS may be required when an additional non-required supplementary function/control is introduced to the flight deck and there is not a requirement to produce a Flight Manual Supplement, for limitation or operational procedures, for example: an optional switch for the control of a non-required system is introduced to the flight deck. The switch does not need be operated in



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relation to any certification requirements or airworthiness limitations and there is not sufficient guidance at the flight deck switch for its purpose. The FCOMS shall detail the purpose and the function of the switch and the associated system, as required. The FCOMS shall be completed on the TEC Manual template, but it should follow the format of the Flight Crew Operating Manual.

References: Procedure 2.33 Part 21.A.31(a), 21.A.107, 21.A.109(a), 21.A.118A(a), 21.A.119, 21.A.120A,

21.A.265(h), 21.A.443, 21.A.449, 21.A.451(b)1



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2.48 Electrical Wiring Interconnection Systems (EWIS) Procedure

Purpose: To provide a means of assessing new or modified EWIS to determine whether

existing EWIS ICA is appropriate. Scope: From the determination of the new or modified EWIS components and their

impact on existing EWIS ICA (if applicable) through to the determination of compliance with the appropriate requirements.

Definitions: AMC – Acceptable Means of Compliance

EWIS – Electrical Wiring Interconnection System EZAP – Enhanced Zonal Analysis Procedure ICA – Instructions for Continued Airworthiness Procedure:

2.48.1 CS 25.1701 and the associated AMC provides a definition of what constitutes EWIS.

This procedure is only applicable to those Design Changes that install or modify EWIS as defined by CS 25.1701 and those that introduce the possibility of new contaminants or combustibles in the zone (for example, adding or revising hydraulic or fuel components by a purely structural design change).

2.48.2 Design Changes / Repairs that do not introduce or modify those items discussed

by 2.48.1 need not follow this procedure and need not comply with the EWIS requirements defined by the Type Certificate Data Sheet.

2.48.3 Certification Memorandum, CM-ES-002, clarifies the certification position

regarding EWIS. 2.48.4 Except for Design Changes defined by 2.48.2, an analysis of newly installed or

modified EWIS components is necessary for any Design Change, to a product certified to the CS/JAR/FAR Part 25 requirements.

2.48.5 The Certification Programme should, as a minimum, describe the following:

2.48.5.1 Provide an identification of the newly installed or modified EWIS components,

2.48.5.2 Identification of the affected zones.



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2.48.6 Depending upon the scale of the EWIS modification, it may be acceptable to provide a justification within the Certification Programme, stating that there is no appreciable affect to the new / modified EWIS and hence allow for agreement that the existing EWIS ICA maintenance tasks remain applicable and appropriate. The justification must be clearly documented and agreed by the Head of the Office of Airworthiness.

2.48.7 The following statement should accompany the justification “The proposed Design Change, in terms of EWIS has been reviewed as per Procedure 2.48. It has been determined that no revision to existing EWIS ICA is necessary and hence no further assessment is required”.

2.48.8 Examples of Design Changes which would have no appreciable effect include, but

are not limited to:

2.48.8.1 Local Pin Strapping where the modification is local to the LRU,

2.48.8.2 Termination/activation of existing wiring (assuming the

addition was analysed in the first place),

2.48.8.3 LRU replacement with minor wiring changes, that are local to the LRU,

2.48.8.4 Relocation of EWIS within the same zone,

2.48.8.5 Removal Design Changes – removal of EWIS components.

Note: In some cases, the relocation and/or removal of EWIS may result in a necessary amendment to the EWIS ICA, i.e. if the components are installed in non-standard locations with limited or very explicit existing EWIS ICA. This must be considered when making any justification. Note: In order to qualify as not-appreciable, the EWIS components and their installation / revision must be selected and conducted in accordance with the TC-Holder standard practices. This must be clearly defined within the justification in the Certification Programme and be documented on the installation drawings, parts lists, accomplishment instructions (as necessary).



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2.48.9 If the introduction / relocation of EWIS is considered appreciable, an EWIS analysis must be conducted within a Technical Report.

2.48.10 The Technical Report should document the following:

2.48.10.1 Purpose of the assessment,

2.48.10.2 Description of the Design Change in relation to the effect on EWIS,

2.48.10.3 Aircraft zones affected by the Design Change,

2.48.10.4 Identification of the applicable EWIS (EZAP) Maintenance Tasks for the affected zone,

2.48.10.5 A completed EWIS flowchart, with appropriate justifications, as per the Certification Memorandum CM-ES-002. The result of the flowchart will determine if the Design Change requires further analysis, or that the Design Change does not require a revision to the EWIS ICA.

2.48.10.6 Conclusion. 2.48.11 If a revision to existing EWIS ICA or new ICA is required, an analysis must be

conducted as per AMC 20-21. This analysis is to be conducted on a separate Technical Report and will assist in the determination of the content of the new / revised ICA material.

2.48.12 The ICA is to be produced as per CS-25 Book 2, AMC to Appendix H25.5 and

contained within STC Twenty One Ltd Technical Publications in accordance with Procedure 2.47.

2.48.13 Any new or revised ICA is to be transmitted as per Procedure 2.18. 27TReferences:27T Procedure 2.18,

Procedure 2.47, Design Procedure DP210, CS25 (incl AMC), FAA AC 25-27A, CM-ES-002.



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2.49 Instructions for Continued Airworthiness Purpose: This procedure sets out the requirements for the preparation of Instructions for

Continued Airworthiness as required under Part 21.A.120A. Scope: Evaluation, drafting and issue of Instructions for Continued Airworthiness (ICA) Definitions: None Procedure: 2.49.1 Instructions for Continued Airworthiness (ICA) can be split into two categories;

Maintenance Instructions and Airworthiness Limitations. ICA are required to communicate inspections / test procedures / part replacement(s) in support of a design change/repair after embodiment. They must be made available to the aircraft/rotorcraft operator during the operational life of the product whilst the design change/repair remains embodied.

2.49.2 Maintenance Instructions are tasks that ensure that the design change remains

serviceable and remains within the original design parameters during its operational lifetime.

2.49.3 Airworthiness Limitations are instructions that must be carried out by the operator

to ensure continued safe flight. As such Airworthiness Limitations are mandatory. Airworthiness limitations are segregated from Maintenance Instructions.

2.49.4 The periodicity of inspections, test procedures or component replacement can be

based on flight cycles, flight hours or calendar intervals. ICA tasks can further classified into inspections, (non-destructive, visual, detailed visual etc.), component replacement, restoration and servicing (e.g. lubrication) STC Twenty One Limited uses the following to generate ICA:-

a. Type Certificate Holder’s existing Maintenance Planning Data b. Certification Specifications – Appendix H c. Maintenance Steering Group (MSG) logic d. System Safety Assessments e. EWIS Procedure – See procedure 2.48

2.49.5 The necessity to generate ICA shall be determined at the change/repair

classification stage as this can affect the classification. Airworthiness Limitations will result in a major design change/repair classification. Airworthiness Limitation instructions that are similar to and included in the Type Certificate Holder’s maintenance programme (based on the maintenance review board report) may



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allow for a re-classification to minor at the discretion of the Head of the Office of Airworthiness.

2.49.6 Maintenance instructions do not normally result in a major change/repair

classification. Where doubt exists advice shall be sought form the Head of the Office of Airworthiness.

2.49.7 As the design change / repair develops, it may be necessary to re-classify the design change IAW procedure 2.10.

2.49.8 The requirement for ICA is recorded in the Certification Programme (see procedure 2.12) against the certification basis for the design change/repair and identifies what existing manuals are affected. In the case of repairs the affected manuals are documented on form S21.45.REP.001 (repair document).

2.49.9 ICA are communicated to the operator via a Supplement manual (See procedure

2.47) and promulgated IAW procedure 2.18. 2.49.10 The effectiveness of the ICA is monitored by STC Twenty One Limited IAW

procedure 2.33. Reportable defects affecting airworthiness that may affect ICA are notified to the Authority IAW procedure 2.7.

2.49.11 The ICA should be written and checked to ensure that all technical and practical

aspects have been considered and addressed. References: 2.7 Occurrence Investigation and Reporting 2.10 Change or Repair Classification Procedure

2.12 Certification Programme, Establish of Certification Basis and Compliance Checklist Procedure 2.18 Document Issue Procedure 2.33 Hazard, Safety, Maintenance Analysis & Continued Airworthiness 2.45 Repairs

2.47 Supplement Manual Procedure 2.48 Electrical Wiring Interconnection Systems (EWIS) Procedure Part 21.A.31(a), 21.A.107, 21.A.109(a), 21.A.118A(a), 21.A.119, 21.A.120A, 21.A.265(h), 21.A.443, 21.A.449, 21.A.451(b)1



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2.50 Permit to Fly & Flight Conditions Approval Purpose: This procedure describes the actions required for STC Twenty One limited to issue

and approve Flight Conditions (FC) and a Permit to Fly (PtF). Scope: From the identification of a requirement for a PtF and FC approval to the issue. Definitions: ‘Safe flight’ means the capability of the aircraft to guarantee, both in flight and on

ground, the safety of the third parties and of their pertinences, of the crew and any other possible occupants, when present [See also GM No.1 to 21.A.708(c)].

Procedure:

PERMIT TO FLY (PtF) & FLIGHT CONDITIONS (FC) ISSUANCE AND APPROVAL 2.50.1 A temporary Permit to Fly is issued when an aircraft is temporarily unable to

comply with the regulations set for the issue of a Certificate of Airworthiness but is still capable of safe flight under defined conditions. The PtF is the responsibility of the State of Registry, so STC Twenty One Limited may only issue FC and PtF in accordance with this procedure (2.50) for G-registered aircraft. For non EU Member State registered aircraft, application for approval of FC may be made to EASA, and for PtF to the State of Registry. As the PtF is a ‘domestic’ document, permission of local NAA(s) is required for performing flight(s) outside the State of Registry airspace.

2.50.2 Flights carried out under a PtF are required for aircraft that do not meet, or have

been shown not to meet, applicable airworthiness requirements but are capable of safe flight under defined conditions (Flight Conditions). Under the scope of approval STC Twenty One Limited are permitted to issue a PtF for the following purposes:-

1. Development; 2. Showing compliance with regulations or certification specifications; 3. Design organisations or production organisations crew training; 4. Flying the aircraft for customer acceptance; 5. Delivering or exporting the aircraft; 6. Flying the aircraft for Authority acceptance; 7. Flying the aircraft to a location where maintenance or airworthiness review

are to be performed, or to a place of storage; 8. Flying an aircraft for trouble-shooting purposes or to check the functioning

of one or more systems, parts, or appliances after maintenance.



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2.50.3 Approval of FC is necessary for the issuance of the PtF.

2.50.4 An application is made for the approval of FC, in the first instance, on form S21.2.50.REP-040 (Flight Conditions – Record of Application). Depending upon the nature of the intended flight, it might not be possible for STC Twenty One Limited to approve FC due to a limitation in the scope of approval. In such cases a further application will be made to the Authority in accordance with 21.A.709.

2.50.5 The Head of Office of Airworthiness (HOOOA) or deputies, has the responsibility

for the issue and approval of FC and PtF.

2.50.6 Approval is granted using the following forms:- 1. Form 18A ‘Flight conditions for a permit to fly’ 2. Form 20b ‘Permit to Fly’.

IMPORTANT NOTES:

3. A form 18A may not be issued by STC Twenty One Limited in respect of an issue of a PtF required for flights as defined in Part 21.A.701(a)15.

4. The approval of FC is related to the safety of the design, when:

a. the aircraft does not conform to an approved design; or b. an Airworthiness Limitation, a Certification Maintenance Requirement or

an Airworthiness Directive has not been complied with; or c. the intended flight(s) are outside the approved envelope; d. the PtF is issued for the purpose of 21.A.701(a)15 [Not Applicable for STC

Twenty One Limited]

5. A copy of Forms 18A and 20b shall be provided to the Authority (defined in 21.A.705) no later than 3 working days following issue from STC Twenty One Limited.

6. The Authority may make or require additional inspections or tests for the

purpose of ensuring that the aircraft is capable of safe flight under the specified conditions and restrictions over and above those specified already by STC Twenty One Limited.

2.50.7 Information in support of a FC approval shall be made using one of the following methods:



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1. For all flights except flight testing, the following details shall be recorded in a

Design Report (See ST21/DOA/HB2 procedure 2.20):-

a. General information on aircraft;

i. Aircraft Manufacturer; ii. Type of Aircraft, Serial Number, Registration marks;

iii. The purpose of the flight;

b. Determination of Conditions/Limitations.

2. When determining conditions and limitations the following areas shall be addressed:-

a. The configuration(s) for which the permit to fly is requested; b. Any condition or restriction necessary for safe operation of the aircraft,

including: c. The conditions or restrictions put on itineraries or airspace, or both,

required for the flight(s); d. The conditions and restrictions put on the flight crew to fly the aircraft; e. The restrictions regarding carriage of persons other than flight crew; f. The operating limitations, specific procedures or technical conditions

to be met; g. The specific continuing airworthiness arrangements including

maintenance instructions and regime under which they will be performed;

h. The substantiation that the aircraft is capable of safe flight under the conditions or restrictions above;

i. The methodology used for the control of the aircraft configuration, in order to remain within the established conditions;

3. Documentation in Support of Proposed Conditions/Limitations;

a. When the limitations and/or the specific conditions for the flight are determined on the basis of analysis and/or tests and/or calculations and other methods, they must be referenced in the Design Report. Each referenced document must also carry, the date of its creation, the signature of the author and of the CVE that approved its content. In cases where documents originating from Type Certificate holder are



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used, they are not required to be submitted to the CVE for their approval.

4. Declaration of Safe Flight

a. The report shall contain a declaration that the aircraft is capable of safe flight under the conditions or restrictions defined therein.

b. A typical example can be found in Appendix 3 to this procedures handbook.

5. For flight testing, a Flight Test Programme shall be developed and documented

using Form S21.2.36.REP.038 (Flight Test Programme) In addition, and prior to each flight, a Flight Test Order (Form S21.2.36.REP.039) shall be completed. Refer to ST21/DOA/HB4 FTOM for details. The Flight Test Programme and Order take into account the foregoing FC considerations.

FLIGHT CREW

2.50.8 Flight crew shall be selected/approved according to the type of flight being undertaken. For flights other than test flights conducted by STC Twenty One Limited (see below) i.e. an operator, STC Twenty One Limited will state any flight crew limitations.

2.50.9 For test flights, including crew training, the crew will be selected according to the

category of test flight. Refer to ST21/DOA/HB4 (Flight Test Operations Manual).

ITINERARIES-AIRSPACE

2.50.10 The flight conditions must state any limitations on the itineraries or Airspace required for safe flight.

2.50.11 The PtF should state its validity - typically, that the PtF is accepted for flights in UK airspace, but that permission of local NAA(s) is required for performing flights outside the State of Registry airspace.

APPROVAL OF FLIGHT CONDITIONS (21.A.710)

2.50.12 Upon determination of applicable conditions/limitations, the HOOOA (or

deputies), when satisfied with the conditions that allow the aircraft to perform a safe flight, will sign Form 18A.



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2.50.13 If the approval of FC is associated with a flight test (excluding flights relating to the showing of compliance where the safety of the design is being demonstrated), the Flight Test Programme (Form S21.2.36.REP.038) is verified and signed by the relevant CVE staff, and is then forwarded, along with the Form 18A, to the Flight Test Manager who, after having approved its contents asks the HOOOA (or deputies), to sign Form 18A.

2.50.14 The HOOOA (or deputies), in collaboration with the Flight Test Manager, if applicable, are responsible for checking approval of FC is obtained.

2.50.15 The approved FC, and all the related documentation, must be filed and must be available to the Authority for the necessary verifications; so that all the information needed to guarantee the aircraft continuing airworthiness is provided.

2.50.16 Changes to the aircraft configuration are managed through the Concession (procedure 2.31), Design Query Note (procedure 2.32) and Master Document List (procedure 2.16) procedures, or any accepted sub-contractor procedures in accordance with an interface arrangement (procedure 2.9). Any change affecting the validity of the FC approval (e.g. changes to a limitation) will result in the invalidation of the Form 18A and will require a new Form 18A to be completed and approved as described previously.

2.50.17 Changes to the conditions or associated substantiations that are approved but do not affect the text on the PtF do not require issuance of a new PtF.

2.50.18 In case a new application is necessary, the substantiation for approval of the FC

only needs to address the change.

PERMIT TO FLY

2.50.19 The process of preparing, managing and filing the issuance of the PtF is carried out by the HOOOA (or deputies), who starts the process by obtaining the approval of FC and associated release of form 18A.

2.50.20 Upon receipt of the finally approved FC the HoOoA (or deputies), must, as applicable:

1. Reserved. 2. In all non-flight-test cases confirmation that the FC require that the CAMO

coordinates with the MOA to ensure that the aircraft is in an approved configuration as stated in the Design Report applicable to the FC;

3. Check, with the possible collaboration of the Head of Design and/or CVEs, the compliance of the flight conditions with all the applicable rules, at the time of



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issuance of the PtF, by submitting the aircraft to all verifications considered as necessary, this including relevant document checks and inspections.

2.50.21 Once the previous actions have been carried out, an Form 20b (PtF) is to be completed. It shall be filled in specifying all the purposes for which the PtF is to be issued, as well as referring to the approved Flight Conditions and restrictions. A copy of the approved FC shall be enclosed with the PtF.

2.50.22 The HoOoA (or deputies), is responsible for the checking and signing of the PtF.

2.50.23 Upon approval of the PtF and FC, the original documents are retained by the DOA, while copies are delivered directly to the crew operating the aircraft.

2.50.24 A copy of the PtF, together with the approved FC, shall be sent for information purposes to the competent authority of the State of Registry, within three days. Evidence must be retained and filed.

2.50.25 A signed PtF cannot be transferred to third parties and therefore, in case of a

change of the DOA having issued this PtF or change of aircraft owner and/or the registration marks, the PtF must be issued again.

2.50.26 In accordance with 21.A.723, the PtF has a maximum validity period of 12 months and is kept valid as long as: 1. The approved FC remain valid; 2. The PtF has not been revoked or returned; 3. The aircraft is registered in the same state; 4. The aircraft is in conformance with the approved FC; 5. No condition affecting the safety of the flight had been detected or

determined. 2.50.27 If, after the issue of the PtF, a failure to follow the above mentioned conditions is

detected, the DOA will immediately revoke the PtF and notify the Authority in a timely manner.

2.50.28 Upon expiration of the period of validity of the PtF, it can be re-issued by carrying out again the whole procedure for the approval of the FC and for the issue of the PtF. The renewal of the permit is never automatic.

2.50.29 STC Twenty One Limited, as the holder of a PtF, shall ensure access to the aircraft to the Authoritie, whenever they request it.



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2.50.30 In order to ensure that all conditions and/or restrictions associated with the PtF are complied with and maintained at the date of issue, whenever deemed necessary, the DOA must carry out the appropriate checks in order to ascertain that the FC and the established limitations are observed. Note that on the FC form, in condition/remarks, it shall be stated that the aircraft operator is responsible for advising the DOA about any modification that is intended to be implemented, post the issue of FC, so that the DOA can take all the necessary actions.

2.50.31 The original copy of the Form 20b (Permit to Fly), together with all the documentation associated with it, shall be filed by the Head of Office of Airworthiness and be available to the Authority for their necessary verifications; so that all information needed to guarantee the aircrafts continuing airworthiness status is provided.

2.50.32 The documents must be kept in the official files for the entire period that the

aircraft to which the official files relate remains in service in order to maintain continued airworthiness.



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Figure 1 – Flight Conditions Approval

References: Handbook 4 FTOM Flight Testing

2.45 Repairs DP104 – Design Change/Repair Job Card Process Part 21.A.35(a)(b), 21.A.243(a)(i), 21.A.263(c)6,7, 21.A.265(f)(g), 21.A.701(a), 21.A.707, 21.A.708, 21.A.710, 21.A.711(b)(e)(f)(g), 21.A.713, 21.A.719(a), 21.A.721, 21.A.723(a)(c), 21.A.725, 21.A.727, 21.A.729.



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2.51 Environmental Protection Purpose: Procedure 2.10 (Change or Repair Classification Procedure Part 21) includes a

definition of change/repair classification i.e. Major and Minor. The classification process requires the DOA to assess potential effects on the airworthiness of the product and environmental protection requirements. In the case of the latter, this procedure describes how STC Twenty One Limited makes such assessments.

Scope: From the identification of a change/repair potentially affecting environmental

protection requirements to the classification and subsequent inclusion into the certification programme.

Definitions: Refer to procedure 2.10 for change classification definitions. Environmental Characteristics: Noise – A change to noise that introduces either;

1. an increase in the noise certification level(s); or 2. a reduction in the noise certification level(s) for which the applicant

wishes to take credit. Emissions – A change that introduces an increase or decrease in the

emissions certification levels. Appreciable Effect - is considered to be one which exceeds the ICAO

criteria for a no-acoustical change or a no-emissions change. 27TProcedure: 2.51.1 All changes and repairs shall be classified in accordance with procedure 2.10. The

following procedure gives specific additional guidance on changes that might affect the environmental characteristics of the product being modified.

2.51.2 Certification Specifications (CS) for aircraft noise are defined in CS-36. Acceptable

means of compliance with the CS are contained within ICAO Annex 16 Volume I. 2.51.3 Certification Specifications for aircraft emissions and fuel venting are defined in

CS-34. Acceptable means of compliance with the CS are contained within ICAO Annex 16 Volume II.

2.51.4 Changes affecting the environmental characteristics of the product, and hence compliance with the applicable CS, shall be documented in the Certification Programme (see procedure 2.12). The certification basis shall include changes to



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environmental protection requirements together with a means of compliance as required.

2.51.5 Paragraph 8 of Appendix A to GM 21.A.91 considers changes and how they might

affect the environmental characteristics of the product. For changes that could appreciably affect noise leading to a major change classification are as follows:

• Changes to take-off mass • Changes to landing mass • Change to centre of gravity limits • Changes to aircraft drag

2.51.6 Paragraph 8 of Appendix A to GM 21.A.91 provides guidance on both small and

large aeroplane and rotorcraft types and should be read in conjunction with this procedure.

2.51.7 Modifications to engines that could affect emission certification are not considered

in this procedure as changes to engines/power-plants are not within the DOA’s scope of approval.

2.51.8 External modifications to an aircraft that change airflow can result in additional

drag, reduce aircraft performance and additional airframe noise. ICAO Annex 16 defines a “derived version” of an aircraft as one which “incorporates changes in type design which may affect its noise characteristics adversely”. Such a change in type design is sometimes referred to as an “acoustical change”. A change in type design that has no appreciable effect on the product’s noise characteristics is a “no-acoustical change” (NAC).

2.51.9 In accordance with Paragraph 8 of Appendix A to GM 21.A.91 generally, installation

of small/low profile antennas do not represent an acoustical change. 2.51.10 Installation of flush or nearly flush repairs do not represent an acoustical change. 2.51.11 Installation of winglets will typically reduce drag and improve aircraft

performance. As such introduction of winglets can be considered as introducing a no acoustical change.

2.51.12 Larger external changes e.g. belly pods will require a deeper analysis into the

effects on aircraft performance e.g. CFD or proposed flight test programme designed to compare an unmodified aircraft (baseline) with a modified aircraft. In the case where aircraft performance is reduced by an appreciable amount, a “write” down will be agreed with the Authority to cover variances in fleet performance and variability in test results. Performance decrements will be normally converted to an equivalent payload weight decrement and promulgated



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to the operator via a supplement to the aircraft flight manual (see procedure 2.29). Employing this method ensures that compliance with environmental protections requirements are maintained.

2.51.13 In determining whether or not an external change will constitute an acoustical

change, a comparison should be made with similar previously approved STCs taking into account aerodynamic profile, position and size. If similarity can be justified, then the change may be considered as being a no-acoustical change.

2.51.14 Where a comparison method is not possible, STC Twenty One Limited shall

contract a DOA having the required terms of approval to assess and approve acoustical changes. This selection shall be made in accordance with procedure 2.8.

2.51.15 If there is any doubt as to the classification of an acoustical change, advice of the

Authority will be sought. 2.51.16 Any acoustical change leading to a major change classification will require STC

Twenty One Limited to apply to the Authority for a Supplemental Type Certificate (See Procedure 2.17) and support from a DOA with the required terms of approval to assess and approve acoustical changes. STC Twenty One Limited may wish to compile compliance documents however compliance verification cannot be made under the STC Twenty One Limited design assurance system unless a major change to the DOA approval is granted requiring a CVE discipline for Environmental Protection.

2.51.17 The foregoing decision process is summarised on a flow chart in Figure 2.51-1. 2.51.18 Any acoustical change not increasing aircraft noise beyond the noise margins

detailed in approved noise levels database will not require aircraft testing.



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Figure 2.51-1



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References: 2.8 Contractor and Sub-Contractor Selection Procedure 2.10 Change or Repair Classification Procedure

2.12 Certification Programme, Establish of Certification Basis and Compliance Checklist Procedure

2.29 Flight Manual Supplement Procedure 2.15 Minor change/repair Approval Procedure

2.17 Major change/repair Approval Procedure 2.45 Repairs Part 21.A.19, 21.A.91, & GM 21.A.91, 21.A.95(b), 21.A.97(b), 21.A.101(a)(b),

21.A.117(a), 21.A.239(c), 21.A.263(c)(1), 21.A.435(a) ICAO Environmental Technical Manual, CS-34, CS-36 ICAO Annex 16 Volumes I & II



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2.52 Wireless LAN Classification Procedure Purpose: To detail the processes that may be undertaken and to provide guidance on the

classification of a Design Change that involves the activation of an on-board wireless local area network (WLAN).

Scope: To assist in the determination of a possible minor classification of a Design Change

that introduces an on-board wireless network (WLAN).

This procedure may be used to assist the Design Change classification in accordance with Procedure 2.10. This procedure and corresponding flowchart provide a set of guidance, that if followed may allow the classification of the Design Change to be “Minor”. The flowchart included in this procedure provides a method with which STC Twenty One Limited will address concerns relating to RF interference of a system or Portable Electronic Device that radiates RF energy.

Limitations: The compliance methods in this procedure have been approved by the Authority.

Any changes to the documented methods of compliance shall be Authority approved. See handbook 1 section 1.3 for the amendment process.

Definitions: Adverse Effect

HIRF effect that results in system failure, malfunction, or misleading information to a degree that is unacceptable for the specific aircraft function or system addressed in the HIRF regulations. A determination of whether a system or function is adversely affected should consider the HIRF effect in relation to the overall aircraft and its operation.

Back-Door Coupling RF energy radiates from the PED and couples directly into the aircraft electrical and electronic equipment, or in to the interconnect wiring. Back door coupling can affect any aircraft electrical and electronic equipment. Back door coupling also includes directly conducted RF energy from the PED, where there is a direct wired connection from the PED to aircraft power, data or control system. This conducted back door coupling can occur with in-seat power supplies or aircraft wires local area networks. Certification Review Item (CRI) A Certification Review Item (CRI) refers to a document which is used to document the certification of an object which requires additional clarification above those considered by the basic airworthiness regulations, i.e. CS 25, or has an outstanding technical or administrative significance.



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Development Assurance Level (DAL) Development Assurance Level, also referred to as DAL or IDAL is a designation that is assigned to a component (hardware or software) as determined by the OEM during the development phase. The DAL establishes the rigour necessary to demonstrate compliance. At the aircraft level, it must be ensured that the defined DAL (hardware or software) correlates to the analysed failure effect and hence will allow for compliance demonstration. Front-Door Coupling RF energy radiates from the PED and couples directly in to the aircraft radio receiver antennas. Front door coupling applies only to aircraft radio receivers.

High Intensity Radiated Frequency (HIRF) High Intensity Radiated Frequency or HIRF refers to radio frequency possessing sufficient energy to adversely affect either a living organism or the performance of a device subjected to it.

Portable Electronic Device (PED) A PED is any piece of lightweight, electrically-powered equipment. These devices are typically consumer electronic devices capable of communications, data processing and/or utility. Examples range from handheld, lightweight electronic devices such as tablets, e-readers, and smartphones to small devices such as MP3 players and electronic toys.

Required System System containing any instrument, equipment, mechanism, part, apparatus, appurtenance, software or accessory, including communications equipment, that is used or intended to be used in operating or controlling an aircraft in flight including parts of an airframe, engine or propeller, or equipment used to manoeuvre the aircraft on the ground. Wireless Local Area Network (WLAN) A Wireless Local Area Network (WLAN) is a wireless computer network that links two or more devices using wireless communication within a limited area, i.e. an aircraft fuselage.

Preamble: The analysis must be documented using STC Twenty One Limited Form

S21.2.26.REP.015 “Technical Report Form” in accordance with Procedure 2.26 to ensure a consistent documentation approach.

Note: The use of a Technical Report Form will, if desired by the author, allow the analysis to aid in the later demonstration of compliance against various airworthiness requirements, i.e. 25.1309.

https://en.wikipedia.org/wiki/Wireless_communication



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Item numbers within the below procedure relate directly to the corresponding items in the flowchart, i.e. 2.52.1 relates to box 1 in the flowchart. 2.52.1 through 2.52.3 are pre-cursors to the analysis and are intended to gather information to be used during the analysis. The technical report must provide detailed justification (including evidence where necessary) to support the decision criterion within each step.

Procedure: 2.52.1 The first step in addressing a classification is to define the required usage of the

installed system and / or PED devices. The aircraft operator must inform STC Twenty One Limited of their intended usage as this will shape the approval and analysis later in the programme. For example:

a) Is the system intended to operate (with representative PED’s) during all flight phases?

b) Is usage required during low-visibility approach operations?

c) Is the system intended to fulfil mandatory requirements (either by regulation or operating rules)?

2.52.2 The HIRF compliance of the aircraft must next be defined. Guidance can be sought

from RTCA DO-307A and EASA Certification Memorandum CS-ES-003. Aircraft that meet the FAA or EASA HIRF regulations or EASA/JAA HIRF Special Conditions are considered PED tolerant for back-door effects. Aircraft that meet with the FAA HIRF Special Condition are not considered PED tolerant as the testing only included systems whose failure or anomalous behaviour would result in a catastrophic failure effect. Should a doubt exist as to the HIRF certification of a product, a Major classification should be sought.

2.52.3 The essential aircraft systems, including those required by the operating rules, must be identified and a core Preliminary Functional Hazard Assessment (PFHA) raised to identify their failure effect (due to failure or anomalous behaviour) as a result of potential RF interference from the installed system or associated PEDs. The analysis must take items 2.52.1 and 2.52.2 in to consideration. The analysis should address individual equipment qualification i.e. RTCA DO-160D Change 1 / Eurocae ED-14D Change 1, Section 20 as defined by Table 3.1 of RTCA DO-307A. Table included below for clarity. If the equipment was tested to the categories defined within this table, the equipment can be considered PED tolerant for the



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effects of back-door coupling. If not, testing at the aircraft level will be required to determine immunity during the identified scenarios. Note: A Certification Review Item (CRI) exists for WLAN projects. The CRI to be referenced is stored electronically in the backup to the procedures and is titled ‘WLAN and interfacing (T-)PEDs Issue 3 Oct 2014’. Should the flowchart result in a ‘Minor’ classification, the appropriate CRI is to be prescribed in to the ‘Additional Requirements’ section of the Certification Programme. The content and compliance will be declared accordingly within the compliance checklist. This ensures a harmonisation with the requirements without enforcing a ‘Major’ classification where one is considered unnecessary.

2.52.4 If the system to be installed is part of a “required system”, either due to analysed

failure effect (per 2.52.3) or by the operating rules, a Major change classification should be sought in line with 21.A.91. If not, proceed to step 2.52.5.



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2.52.5 Certification Memorandum CM-ES-003 states that analysis of “Front-door” coupling effects is only required for a design change that introduces a wireless communication system to be used in all flight phases, including low visibility approach operation. If system usage during low visibility approach operations is not required, analysis of “Front-door” coupling effects is not required and no further action is necessary.

2.52.6 If analysis is required per 2.52.5, testing will be necessary in order to demonstrate

compliance. Applicable means of demonstrating compliance is contained within RTCA DO-307A. If testing for immunity to “Front-door” coupling is required the Design Change must be classified Major due to a potentially “Major”, “Hazardous” or “Catastrophic” failure effect for which mitigation will not be possible until the latter stages of the Design Change.

Note: An assessment against the effects of “Back-door” coupling must also be completed under this scenario.

2.52.7 Aircraft HIRF Qualification Acceptable? As per section 2.52.2, there are two possible scenarios for section 2.52.7. Either: Aircraft that meet the FAA or EASA HIRF regulations or EASA/JAA HIRF Special Conditions are considered PED tolerant for back-door effects, or: Aircraft that meet with the FAA HIRF Special Condition are not considered PED tolerant as the testing only included systems whose failure or anomalous behaviour would result in a catastrophic failure effect.

2.52.7.1 If the aircraft is considered PED tolerant as per the FAA or

EASA HIRF regulations or EASA/JAA HIRF Special Conditions, proceed to step 2.52.8.

2.52.7.2 If the aircraft is not considered PED tolerant, or meets with

the FAA HIRF Special Condition, proceed to step 2.52.9. 2.52.8 If 2.52.7.1 above is met, the next step is to identify and review all equipment,

required for safe flight that has been introduced to the aircraft post TC issuance (hence not addressed by the TC-Holder derived HIRF certification) and declare a failure effect due to the failure and / or anomalous behaviour. The review should address individual equipment qualification i.e. RTCA DO-160D Change 1 / Eurocae ED-14D Change 1, Section 20 as defined by Table 3.1 of RTCA DO-307A. Table included above for clarity. If the analysed failure effect (or no third-party equipment has been introduced) is one of “Minor” or less severe, a “Minor” classification should be sought (in line with GM 21.A.91). If however, the analysed failure effect is one of a potentially “Major”, “Hazardous” or “Catastrophic” event as a result of RF interference, a “Major” classification must be sought (in line with GM 21.A.91) and appropriate aircraft level testing must be performed.



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Note: Particular attention must be given to the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) as per Table 3-1 of RTCA DO-307A.

2.52.9 If 2.52.7.1 above is not met and 2.52.7.2 is followed, the next step is to review

equipment identified as having a failure classification of “Major” or more severe and equipment that is required by the operating rules, i.e. CVR and FDR. The review should address the individual equipment qualification i.e. RTCA DO-160D Change 1 / Eurocae ED-14D Change 1, Section 20 as defined by Table 3.1 of RTCA DO-307A. Table included above for clarity. If the analysed failure effect, taking in to consideration the above review is one of “Minor” or less severe, a “Minor” classification should be sought (in line with GM 21.A.91). If however, the analysed failure effect remains one of a potentially “Major”, “Hazardous” or “Catastrophic” event as a result of RF interference, a “Major” classification must be sought (in line with GM 21.A.91) and aircraft level testing must be completed in order to demonstrate compliance to 2X.1309. Note: If MoC 6 testing is necessary to determine the immunity of a system analysed as having a potentially “Major”, “Hazardous” or “Catastrophic” failure event, a “Major” classification must be sought as the mitigation would not be forthcoming until the latter stages of the Design Change.

2.52.10 Means of Compliance CRI ‘WLAN and interfacing (T-)PEDs Issue 3 Oct 2014’ must

always be included in the certification basis for the design change (see Procedure 2.12 Certification Programme Procedure).

2.52.11 Any condition met to derive a minor design change classification at the equipment

level, for example a pre-requisite configuration, must be listed as a concurrent requirement for the embodiment of the change in the Accomplishment Instructions.

Note: If an AFM supplement is required to provide operating limitations, non-normal and/or emergency procedures, this shall be classified in accordance with Procedure 2.10, and compiled and issued in accordance with procedure 2.29.



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Flowchart:

2. Determine the HIRF compliance of the aircraft

3. Identify Systems (DO-307A, Table 3.1)

Yes

1. Define the operators required usage

5. Low-Visibility Approach

Operations?

4. Is the System Required?

6. Front Door Coupling Assessment Req'd

Back Door Coupling Assessment Req'd

MAJOR CLASSIFICATION


Design Change classified as Major per 21.A.91 and Procedure 2.10

A

No

Yes

No



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Flowchart: Cont.

7. Aircraft HIRF

Qualification Acceptable?

8. Review Third-Party Equipment

9. Analysis of Essential Equipment

Acceptable Qualification?

Acceptable Qualification?


A

No

Yes

Yes

No

MINOR CLASSIFICATION


No

Yes

MINOR CLASSIFICATION



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References: Procedure 2.10 - Change or Repair Classification Procedure

Procedure 2.21 - Test Plan Procedure. Procedure 2.22 - Test Report Procedure. Procedure 2.24 - Equipment Qualification Procedure. Procedure 2.29 - Flight Manual Supplement Procedure. Procedure 2.33 - Hazard, Safety, Maintenance Analysis and Continued Airworthiness Procedure. CS 23.1309(b)(1), 25.1309(a)(1), 27.1309(a), 29.1309(a), 25.1353(a), 23.1431(a), 25.1431(a), 29.1431(a), 23.1529, 25.1529, 27.1529, 29.1529. RTCA/DO-307A December 15, 2016 - Guidance to Certify an Aircraft as PED tolerant. Certification Memorandum - CM-ES-003 - Guidance to Certify an Aircraft as PED tolerant. Part 21.A.91, 21.A.95, 21.A.97



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2.53 Approved Model List (AML) Design Changes Purpose: To explain the use and provide guidance for Approved Model List STCs or Minor

Changes. There are certain design changes that do not have to be type specific. For example, an aircraft part that meets a specification (e.g. ARINC) that could be form, fit and functionally interchangeable with existing parts that performs the same function could be used on various aircraft types having the same mechanical and electrical interface with no impact on the aircraft operation. An AML design change approval is particularly suited to this type of scenario.

Scope: To determine if a design change is suitable to be approved as an AML, define the

application process and the necessary configuration control through to approval and subsequent changes.

Definitions: Approved Model List (AML) – An AML change is a multi-model and multi-type

change that allows a set of compliance data to become applicable to various aircraft TCs under a single STC Major Change or Minor Change approval.

Procedure: General Considerations 2.53.1 An AML approval may only be issued for aircraft that are type-certificated against

the same product category of the selected airworthiness code (e.g., an AML STC for an aircraft certificated under CS-23 cannot include aircraft certificated under CS-25, 27 or 29).

2.53.2 The AML approval will not be suitable in cases where type or model specific

compliance demonstration is required, for example:

a. Those for systems that can directly control the aircraft and are dependent on aircraft feedback for design like most autopilot installations or similar systems that involve control inputs.

b. When each installation needs to have a separate compliance demonstration as e.g. for electromagnetic compatibility, HIRF or lightning effects.

2.53.3 When seeking an AML change it is important to co-ordinate early with the Head of

Office of Airworthiness to determine any issues that may have an impact on a multi-model/type installation approval.



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2.53.4 An AML design change must follow 21.A.101, in that a harmonised Certification Basis must be selected for all applicable aircraft models.

2.53.5 Data used for compliance demonstration for the approval of a design, irrespective

of classification, shall be valid for every model on the AML (i.e. covering all differences between the applicable models). The AML change process is only valid where it can be shown that the design, function, installation and operation are identical or similar (i.e. changes to interfaces based on type differences) across types whilst sharing the same certification baseline data and that compliance demonstration is identical for all aircraft models included within an AML change. If commonality cannot be established, an AML approval is not the proper method of approval.

Qualification / Applicability 2.53.6 The below checklist taken from EASA Certification Memorandum CM-21.A-E001

Issue 01 outlines if an AML is a suitable approval.

1. Aircraft models/types on the AML share the same certification baseline data.

2. The purpose of the modification (i.e. functionality) is the same for all impacted aircraft models/types.

3. Installation similarities that exist between the proposed models and those areas of the modification that are different from the rest of the models are properly documented.

4. A common set of CS, SC, ESF, etc. corresponding to the most stringent certification basis of all the model/types included in the AML is established that is covering all affected certification bases, or a common unique certification basis corresponding to the most stringent certification basis of all the model/types included in the AML or according to later effective amendments is established.

5. Complete compliance is demonstrated for the modification to the affected areas for each aircraft model/type listed in the AML.

6. Aircraft Flight Manual Supplement (AFMS), if applicable, are pertinent to each specific model.

7. Installation instructions are adequate to allow for a consistent and compliant installation on each model in the AML. Clear boundaries are established and documented.

8. ICA, if needed, are applicable to each model in the AML.

9. OSD impact is assessed against each impacted model in the AML. When an impact is identified, OSD is made available as required.



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Classification 2.53.7 AMLs may be suitable for either Minor or Major changes. All changes will be

classified in accordance with procedure 2.10. Aircraft Flight Manual 2.53.8 The Aircraft Flight Manual Supplement, if issued, must be made applicable to each

model of the AML Change as per section 21.A.119 or 21.A.57 as applicable. The Flight Manual Supplement shall be completed as per procedure 2.29

Note: If a particular change installation introduces unique operational

characteristics in a particular aircraft model/type with respect to the others in the AML (thus requiring a highly customized FMS per aircraft model/type), it will be necessary to seek a separate STC, Major Change or Minor Change approval.

Installation Instructions and Instructions for Continued Airworthiness 2.53.9 The installation instructions must describe the installation in adequate detail such

that follow-on installations are repeatable and result in a consistent and compliant installation for every model when properly followed.

2.53.10 It is permissible to have ‘different’ installation instructions, drawings etc, however

it must be explicit as to which model they apply. Accomplishment Instructions, as per procedure 2.34 will be used and can include a general section with specific model appendices to address individual installation requirements. The key is to provide these instructions and alternatives during the Certification Programme, as part of the AML Change approval.

2.53.11 Instructions for Continued Airworthiness will be created in accordance with

procedure 2.49. Operational Suitability Data (OSD) 2.53.12 OSD, if issued, must be made applicable to each model of the AML Change and

completed in accordance with procedure 2.43. 2.53.13 If a particular change installation introduces unique operational characteristics in

a particular aircraft model/type with respect to the others in the AML (thus requiring highly customized OSD per aircraft model/type), it will be necessary to seek a separate STC, Major Change or Minor Change approval.



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Changes to an AML Change 2.53.14 Changes to an AML Change are classified and managed as per procedure 2.10. 2.53.15 The addition of the aircraft models to an AML STC is considered a Major Change. 2.53.16 If there are instances where an upgrade to existing hardware or components

approved by the AML (such as a software revision), consideration should be given to ensure that the new revision does not have unintended consequences that affect a prior approval of any of the affected models.

2.53.17 When adding new model(s) or amending an existing model, an AML Change

approval allows the use of previously submitted compliance data that are applicable without the need for further review. If adding a new model that has differences from the previously approved models, then further substantiation may be required to address those differences. The AML Change is not a means to approve additional models without further substantiation. Nevertheless, the technical re-investigation needed should be limited in scope; if an extensive re-investigation is necessary, the modification does not meet the condition for the AML Change. Coordination with the Authority will be necessary to assess the suitability of the technical investigation scope increase.

2.53.18 The aircraft configuration shall be tabulated using STC Twenty One Ltd Form

Number S21.2.53.REP.001 to accurately maintain the configuration control of an AML.

References: 2.10 Change/Repair Classification Procedure 2.15 Minor change/repair Approval Procedure 2.17 Major change/repair Approval Procedure 2.29 Flight Manual Supplement Procedure 2.34 Accomplishment Instructions Procedure

2.43 Operational Suitability Data (OSD) Supplement Procedure 2.49 Instructions for Continued Airworthiness 2.51 Environmental Protection 2.52 Wireless LAN Classification Procedure Part 21.A.91, & GM 21.A.91, 21.A.95, 21.A.97, 21.A.101, 21.A.117, 21.A.119,

21.A.120A, 21.A.239(c), 21.A.263(c)(1)(2), EASA Certification Memorandum CM-21.A-E-001 Issue 01



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SECTION 3 – APPENDICES



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Appendix 1 - Master Form List Form No. Title

Form 18A Flight Conditions for a Permit to Fly – Approval Form Form 20b Permit to Fly S21.FRC.REP Flight Release Certificate S21.FTS.REP Application for Issue of Permit to Fly S21.2.5.REP.001 CVE Checklist S21.2.6.REP.000 Certifying Staff Record Form S21.2.9.REP.001 POA – DOA Arrangement Form S21.2.9.REP.002 DOA – DOA Arrangement Form S21.2.9.REP.003 DOA – Individual Arrangement Form S21.2.9.REP.004 DOA – MOA Arrangement Form S21.2.9.REP.005 DOA-DO-MOA Arrangement Form S21.2.9.REP.006 DOA – DO Arrangement Form S21.2.9.REP.007 DOA – Test House Arrangement Form S21.2.10.REP.003 Classification Checklist S21.2.12.REP.005– MAJ Certification Programme - Major Changes S21.2.12.REP.005– Major Matrix S21.2.12.REP.006– MIN Certification Programme - Minor Changes S21.2.12.REP.006– Minor Matrix S21.2.16.REP.008 Master Document List S21.2.20.REP.009 Design Report S21.2.21.REP.010 Test Plan S21.2.21.REP.037 Conformity Inspection S21.2.22.REP.011 Test Report S21.2.23.REP.012 Service Bulletin S21.2.24.REP.013 Equipment Approval Form S21.2.25.REP.014 Declaration of Design and Performance S21.2.26.REP.015 Technical Report S21.2.28.REP.017 Design Office Instruction S21.2.29.REP.018 Flight Manual Supplement S21.2.29.REP.036 FMS Amendment Classification S21.2.30.REP.019 Electrical Load Analysis Report S21.2.31.REP.020 Concession Application S21.2.32.REP.021 Design Query Note S21.2.33.REP.024 Occurrence Assessment Report S21.2.33.REP.025 Occurrence Assessment Report Action Item S21.2.34.REP.022 Accomplishment Instructions S21.2.34.REP.045 Work Instruction S21.2.36.REP.038 Flight Test Programme S21.2.36.REP.039 Flight Test Order S21.2.36.REP.044 Flight Test Crew Competency Record S21.2.39.REP.043 Master Form Change S21.2.43.REP.027 Master Minimum Equipment List



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Form No. Title

S21.2.43.REP.028 Cabin Crew Data Manual S21.2.45.REP.001 Repair Document S21.2.46.REP.035 Statement of Approved Design Data S21.2.47.REP.042 Tec Manual S21.2.47.REP.043 Instructions for Continued Airworthiness S21.2.47.REP.044 Illustrated Parts Catalogue Supplement S21.2.47.REP.045 Maintenance Planning Document Supplement S21.2.47.REP.046 Wiring Diagram Manual Supplement S21.2.48.REP.036 Enhanced Zonal Analysis S21.2.50.REP.040 Flight Conditions Application S21.2.50.REP.041 DOA-CAMO Arrangement Form S21.2.53.REP.001 AML S21.AUD.REP.029 Audit Response Form S21.AUD.REP.030 Audit Summary Form S21.AUD.REP.032 Vendor / Sub Contractor Audit Form S21.AUD.REP.033 Sub-Contract Audit Response Form S21.AUD.REP.034 Audit Review



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© STC Twenty One Limited own the copyright of this document which is supplied on the express condition that it is not reproduced or used for any purpose other than that for which it is supplied and it is not communicated to any other person without the prior permission of STC Twenty One Limited

Appendix 2 - Approved Signatory Matrix The following Table defines the Approved Signatories for the various disciplines/tasks that may be performed under DOA nr. UK.21J.0198:

Person Discipline: Areas of Expertise Aircraft Type Activity Limitations CSR

Number Initial Name CVE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 CS 23 CS25 CS27 CS29 Test Wit ICA

1 PG Peter Gaughan ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

May not act as a Signatory for Performance or Flight Handling (Panel 1).

May not act as Signatory for Rotorcraft human external cargo restraint for Cabin Safety (Panel 11).

2 JD John Dent ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

May not act and Approver or CVE for Avionic element (Panel 6) for Major Changes.


3 MH Matt Hubbard ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

May not act as Approver or CVE for any Discipline.

Limited to drawing check for Electrical Systems (Panel 5) and Avionics Systems (Panel 6).

4 PC Paul Culley ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ None

5 AE Alastair Erskine ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ May only act as a Signatory for Flight Manual Supplements

(Panel 1)

6 PS Paul Salt ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ May only act as CVE for Air Conditioning Systems.

7 AJ Alex James ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ May not act as Approver or CVE for any Discipline.

8 AK Anastasios Kokkalis (Prof.)

✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ May only act as a Signatory for Flight Test, Handling Qualities and Performance (Panel 1)

9 LB Les Bent ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ None

10 JH Jerrod Hartley ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ None

11 DG Daniel Griffith ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ None

12 SH Sean Hinds ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ May not act as a Signatory for Performance or Flight Handling (Panel 1).

13 SG Simon Gaughan ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

May not act as CVE or Approver for any discipline.

May act as test witness for Flammability only.

14 TM Taylor Muncy ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘


15 DW Daniel Walder ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘

May not act as Approver or CVE for primary composite structure element of Changes.

May not act as CVE for CS 25.562 (or equivalent)

16 DH Derek Harper ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ ✘ May not act as Approver or CVE for any discipline.

17 RSV 18 RSV 19 RSV 20 RSV



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Discipline Matrix

Category Approval Category

Discipline: Areas of Expertise

Flight and Human Factors 1

Flight test (for all relevant CS Subparts) - Handling qualities- Performance - Human factors- Human machine interface and cockpit integration- Flight manual

OSD-FC 2 - Operational Suitability Data- Flight Crew

Structures 3

Loads, weight and balance - Static Strength - Fatigue and damage tolerance- Materials & manufacturing- Aeroelasticity, vibration and buffeting - Crashworthiness - Decompression - Impact conditions

Hydromechanical Systems 4

Flight Control System (FCS) [ATA 270 on aeroplane / 670 on rotorcraft] - High lift system [ATA 275]- Hydraulics [ATA 290]- Landing gear systems and wheels, tyres & brakes [ATA 320]- Fuselage doors [ATA 520]- Helicopter hoist installation - RAM Air Turbine (RAT) mechanical systems

Electrical Systems* 5

Electrical generation and distribution - Electromagnetic Compatibility (EMC)- High Intensity Radiated Field (HIRF) and lightning indirect effects- Lightning direct effects - Electrical Wiring Interconnection System (EWIS)- Lights - In-Flight Entertainment (IFE) and power outlets (for passengers or crew)- Wireless transmission capabilities (for passengers or crew).

Avionics Systems** 6

Autoflight systems Includes auto-pilot, auto-throttle, flight guidance, flight envelope, stability, etc. - Communications, navigation & surveillance Includes air data systems, datalink,transponder, radio, environment surveillance systems (TCAS, TAWS, Weather Radar …), etc.- Flight Management System (FMS)- Indicating, alerting & recording systems, diagnostic and maintenance systems Includesdisplay systems, instrument and control panel, recorders, vibration/vehicle monitoring system, general computers, central warning systems, maintenance systems, etc.- Integrated Modular Avionics (IMA) Includes IMA resources, databuses - Cybersecurity

Powerplant Installation and Fuel Systems

7

- Engine, propeller and APU installation - Fuel systems- Fuel tank inerting - Extended Diversion Time Operation (EDTO) / Extended Twin Engine Operations (ETOPS)- Fire protection (unpressurised areas)- Volcanic ash

Environmental Control Systems (ECS)

8

- Air conditioning and pressuration - Ice protection - Oxygen systems- Bleed air- Water and waste

Noise, Fuel Venting and Emissions

9 - Noise - Emissions & Fuel venting



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Discipline Matrix

Category Approval Category

Discipline: Areas of Expertise

Software, Airborne Electronic Hardware (AEH), Development Assurance (DA)

10 - Development Assurance (DA), system/aircraft level- Software - Airborne Electronic Hardware (AEH)

Cabin Safety 11

Cabin Installation (including Emergency Medical Systems, VIP interiors, Crew Rest Compartments, Courier Compartments, etc.) - Flight Deck installation - Cargo compartments (installation & restraint)- Occupant crashworthiness/restraint- Fire Protection - pressurised areas (active and passive)- Occupant evacuation - Internal and external placards and markings.- Rotorcraft human external cargo restraint- Security aspects

Safety Assessment (SA) 12 Safety Assessment

Transmission 13 - Rotorcraft transmission

ICA 14 - Instructions for Continued Airworthiness- Maintenance Review Board (MRB) process

OSD-MMEL 15 - Operational Suitability Data– Master Minimum Equipment List

OSD-SIM 16 - Operational Suitability Data- Simulator

OSD-CC 17 - Operational Suitability Data- Cabin Crew

OSD-MCS 18 - Operational Suitability Data- Maintenance Certifying Staff

Propulsion 19

Engine certification - APU qualification - Propeller qualification - Electrical propulsion

Notes: *excludes primary generation systems **excludes non-(E)TSO’d with Software failures considered Major or more severe.

APPROVAL SIGNATORIES The following table defines the approved signatories eligible to sign for final release of documents:

Documents released under the privilege 21.A.263c(2);

Function Signatory

Minor Design Change / Repair Approval HoD

Statement of Approved Design Data (minor) HoD

Documents released under the obligation of 21.A.265(h) “The technical content of this document is approved under the authority of the DOA ref. UK.21J.0198”;

Function Signatory



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Drawing Office Instruction HoD

Accomplishment Instructions HoD

Supplement Manual, inc. FMS, AMMS, IPCS, WDMS, TEC HoD

Service Bulletin HoD

Deputies can sign in place of the main signatory in accordance with Handbook 1, section 1.7.5.2



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APPROVED SIGNATORIES

NAME SAMPLE SIGNATURE

Mr Alastair Erskine

Prof. Anastasios Kokkalis

Mr Daniel Griffith

Mr John Dent

Mr Jerrod Hartley

Mr Les Bent

Mr Paul Culley

Mr Peter Gaughan

Mr Simon Gaughan

Mr Sean Hinds

Mr Taylor Muncy

Mr Paul Salt

Mr Daniel Walder



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Mr Matthew Hubbard

Mr Alex James

Mr Derek Harper



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Appendix 3 - EXAMPLE DESIGN REPORT FOR THE SUBSTANTIATION OF FLIGHT CONDITIONS APPROVAL NOT RELATED TO FLIGHT TEST

Important Note: This appendix is to be used for guidance only for the compilation of a design report as per procedure 2.50. This is NOT a template as the reasons for a FC/PtF approval are varied. Advice should be sought from the Head of the Office of Airworthiness where doubt exists.

1. Purpose

1.1. The purpose of this Design Report is to establish and substantiate the conditions for safe flight for a customer requested flight for the following purpose:

1.1.1. Obtain the reason from the Flight Conditions Application Form

1.2. The Flight Conditions established by this Design Report, when approved, will be transcribed to a Flight Conditions Approval to facilitate the issuance of a Permit to Fly, issued by STC Twenty One Limited under the privilege of 21.A.263(c)(7)*.

1.3. The Flight Conditions Approval and Permit to Fly* will be issued to the aircraft operator.

* Note: When applicable

1.4. This Design Report will define and establish the following:

1.4.1. The configuration of the aircraft on which the Flight Conditions and associated Permit to Fly will be approved;

1.4.2. Any condition or restriction necessary for safe operation of the aircraft which may include:

a) The conditions or restrictions put on itineraries or airspace, or both,required for the flight(s);

b) The conditions and restrictions put on the flight crew to fly the aircraft;c) The restrictions regarding carriage of persons other than flight crew;d) The operating limitations, specific procedures or technical conditions to

be met;e) The specific continuing airworthiness arrangements including

maintenance instructions and regime under which they will beperformed.



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1.4.3. The substantiation that the aircraft is capable of safe flight under the conditions or restrictions above.

1.4.4. The methodology used for the control of the aircraft configuration, in order to remain within the established conditions.

2. Introduction

Explain the reason for the permit request i.e. why the aircraft certificate of airworthiness ceases to be in force.

2.1. On the subject aircraft, the left hand Main Landing Gear support trunnion bearing holes were discovered to have corrosion beyond acceptable limits. This was both on the face and within the bore of the trunnion. The corrosion was discovered during landing gear replacement.

2.2. The operator has requested approval for a ferry flight to permit the transit of the

aircraft to an appropriate, approved maintenance facility to complete the rectification.

2.3. In support of this ferry flight, the aircraft operator has made a request for support, and obtained a “No Technical Objection” (NTO) from the TC-Holder, (per Appendix XX). The NTO permits one (1) ferry flight, with a possible intermediate stop (two flight cycles maximum) provided a visual inspection of the LH MLG trunnion support is accomplished after each landing.

2.4. STC Twenty One Limited will review the suggested limitations, and include as necessary within the defined Flight Conditions.

2.5. In addition, STC Twenty One Limited will add any additional, pertinent limitations within the defined Flight Conditions.

3. Aircraft Details

3.1. The aircraft for which the Flight Conditions and Permit to Fly is requested for is detailed below:

3.1.1. Aircraft Type: Large Aeroplane. 3.1.2. Aircraft manufacturer: 3.1.3. Aircraft model: 3.1.4. Aircraft registration: 3.1.5. Aircraft MSN: 3.1.6. Aircraft Flight Hours: 3.1.7. Aircraft Flight Cycles: 3.1.8. Purpose of the flight: Flying the aircraft to a location where maintenance



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or airworthiness review are to be performed, or to a place of storage (see note below). Note: Refer to the Flight Conditions Application Form for the specified purpose of flight.

4. Aircraft Configuration

This section only needs to define the aircraft configuration as much as required for this FC approval i.e. since the C of A ceased to be in force.

4.1. The aircraft had a valid C of A and ARC prior to the maintenance findings (per 0) and hence was in an airworthy configuration.

4.2. The operator has also confirmed, via formal declaration (Appendix XX) the following:

4.2.1. All applicable Airworthiness Directives have been identified and complied

with. 4.2.2. All life limited and hard time components are within the specified MPD life

limitations. 4.2.3. The aircraft has been maintained to an approved maintenance programme

(XXXXX, Revision YY, dated DD/MM/YYYY) and that there is no outstanding maintenance.

4.2.4. There are no unapproved Changes. 4.2.5. There are no unapproved repairs. 4.2.6. Except for the subject items described in the Introduction, the aircraft is free

from any defects (including MMEL items). 4.2.7. There are no missing items as per the configurations deviations list (CDL).

4.3. There is no identified requirement to re-configure, or further define the aircraft

configuration for the purposes of this flight, with the exception that, in order to avoid any possible alleviation under MEL or other means, all flight crew emergency equipment must be present.

5. Aircraft Non-conformity assessment.

The intention of this section is to document the assessment of the aircraft non-conformance to the type design e.g. damage, exceeded AD interval etc.

5.1. The operator has confirmed that the aircraft has been fully maintained in accordance

with their approved maintenance programme. During landing gear replacement, (required as a life-limited part and due to be replaced by 1st May 2020), the subject corrosion at the LH MLG trunnion support was discovered. The landing gear



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replacement has been completed. 5.2. The corrosion is hence the only non-conformity requiring assessment.

5.3. The Type Certificate Holder, has assessed the corrosion and provided their statement

of No Technical Objection (NTO) for a single ferry flight, with a possible intermediate stop (two (2) flight cycles maximum) provided a visual inspection of the LH MLG trunnion support is accomplished after each landing.

5.4. The effect of the corrosion will not cause significant strength degradation, will not

substantially worsen during the time required for the ferry flight, and is not likely to cause cracking provided landings are limited per the NTO.

5.5. To alleviate risk of developing cracking at the corrosion site, the landings are to be

made under as low a weight as possible, by flying with no cargo. 6. Assessment of other flight conditions:

The section describes an assessment against the specified chapters in Part 21 and handbook 2 procedure 2.50. These headings should not be changed.

6.1. Itinerary/airspace:

6.1.1. The ferry flight is to be from Leipzig Airport, Germany (LEJ) to Budapest

Airport, Hungary (BUD); 6.1.2. The operator shall be responsible for filing a flight plan prior to the ferry flight.

6.2. Flight crew conditions/restrictions:

6.2.1. The flight shall only be conducted by pilots complying with the requirements

of Commission regulation (EU) No. 1178/2001, holding a valid licence appropriate to the category of aircraft, issued in accordance with Part-FCL and be duly authorised by the aircraft owner/operator to conduct the flight.

6.2.2. Flight crew shall be limited to those essential for safe operation of the aircraft.

6.3. Carriage of other persons:

6.3.1. Passengers shall not be carried.

6.4. Operating limitations:

6.4.1. The flight is to be non-revenue. 6.4.2. No cargo shall be carried.



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7. Continued Airworthiness Arrangements

In order for safe flight, continuing airworthiness arrangements must be in place. This section is used to describe these arrangements.

7.1. The aircraft is being maintained as described and declared in Appendix XX.

7.2. Continued airworthiness falls under the responsibility of the CAMO.

7.3. Operator and TCH mandated daily and pre-flight inspections must be performed prior

to flight. 7.4. If an intermediate landing is made, a visual inspection of the LH MLG trunnion support

is to be made prior to onward flight. 8. Substantiations for safe flight

This section must substantiate those flight conditions required specifically for the deviation from the type design and derivation of said flight conditions. Reference to other sections of the report is acceptable but if separate substantiation is made e.g. structural report / DTA etc. then reference must be documented here. As documented elsewhere in this report:

8.1. A letter of No Technical Objection has been received from the TCH, permitting one (1)

ferry flight.

8.2. The aircraft had a valid Certificate of Airworthiness prior to the issue being found.

8.3. The aircraft is maintained in accordance with an approved maintenance programme.

8.4. The CAMO has declared there are no overdue Airworthiness Directives or Life Limited Parts (critical) - ref. Appendix B.

The following conditions are therefore derived.

9. Flight Conditions

This list must contain the flight safety derived conditions and should include those limitations issued by the TC holder and any other as required by the DOA. 9.1 must be included as revenue flights are not permitted under a PtF. Serious consideration should be given to allocating responsibility for complying with the flight conditions (e.g. CAMO for 9.6, Captain for all other conditions in the example that follows). Such definition of responsibilities can focus the obligation of various parties to adequately support the proposed flight, and provide the



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assurance/evidence that conditions are met such that a PtF may be issued.

9.1. The flight must be non-revenue.

9.2. The carriage of passengers is not permitted. 9.3. The carriage of cargo is not permitted.

9.4. Flight crew shall be limited to the minimum necessary for safe flight.

9.5. All flight crew emergency equipment must be present and fully serviceable.

9.6. The aircraft shall be maintained per the approved maintenance programme, with all

maintenance up to date prior to flight including all Airworthiness Limitations.

9.7. Operator and TC-Holder mandated daily and pre-flight inspections must be conducted prior to flight.

9.8. In the event of an intermediate landing being made, a visual inspection of the LH MLG

trunnion support is to be made (in addition to the requirements of 9.6 and 9.7) prior to onward flight.

9.9. The aircraft shall not be flown outside of TCDS/AFM limitations.

9.10. The aircraft shall only be operated for one (1) flight from Leipzig Airport, Germany (LEJ) to Budapest Airport, Hungary (BUD) with a suitable diversionary airfield taking into consideration Flight Condition 9.8, as required by the operator’s standard operational procedures and the AFM. The operator shall file a flight plan prior to the ferry flight.

9.11. The flight shall only be conducted by pilots complying with the requirements of EU Commission Regulation (EU) No. 1178/2001, holding a valid licence appropriate to the category of aircraft issued in accordance with Part-FCL.

9.12. The Captain must brief the First Officer of all Flight Conditions prior to flight to ensure a thorough understanding.

9.13. The Captain is responsible for ensuring that these Flight Conditions are complied with. 10. Declaration of Safe Flight

10.1. This report establishes flight conditions under which the subject aircraft detailed in this report may be safely flown.