JAR-FAR 25

SECTION 1

SUBPART A -GENERAL

JAR 25.1 Applicability

(a) This Code prescribes airworthiness

JAR-25

standards for the issue of type certificates, and changes to those certificates, for Large Turbine- powered Aeroplanes.

(b) Each person who applies for such a certificate or change must show compliance with the applicable requirements in this Code.

JAR 25.2 Special retroactive requirements

(None applicable for JAR-25.)

INTENTIONALLY LEFT BLANK

INTENTIONALLY LEFT BLANK

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JAR-25

SUBPART D - DESIGN AND CONSTRUCTION

JAR 25.607(a) (continued)

GENERAL

JAR 25.601 General

(2) Its loss could result in reduction in pitch, roll or yaw control capability or response below that required by Subpart B of this The aeroplane may not have design features or

details that experience has shown to be hazardous or unreliable. The suitability of each (b) The fasteners specified in sub-paragraph questionable design detail and part must be (a) of this paragraph and their locking devices established by tests. may not be adversely affected by the

environmental conditions associated with the particular installation.

JAR-25.

JAR 25.603 Materials {For Composite Materials see ACJ 25.603.) (c) No self-locking nut may be used on any

bolt subject to rotation in operation unless a non- The suitability and durability of materials used

for parts, the failure of which could adversely friction -locking device is used in addition to the self-locking device.

affect safety, must - (a)

or tests; Be established on the basis of experience JAR 25.609 Protection of structure

0 Each part of the structure must (see ACJ (b) Conform to approved specifications

(such as industry or military specifications, or Technical Standard Orders) that ensure their (a) Be suitably protected against having the strength and other properties assumed deterioration or loss of strength in service due to in the design data; and any cause, including -

environmental conditions, such as temperature and humidity, expected in service.

25.609) -

(c) Take into account the effects of (1) Weathering;

(2) Corrosion; and

(3) Abrasion; and

JAR 25.605 Fabrication methods

The methods of fabrication employed in the Primary Structure must be such as to produce a consistently sound structure which must also be reliable with respect to maintenance of the original strength under reasonable service conditions. Processes and process control must ensure that it is unlikely that a major defect will remain in any primary structural component after manufacture (for example in complex forgings).

(b) Each new aircraft fabrication method must be substantiated by a test programme.

(a)

JAR 25.607 Fasteners

(b) Have provisions for ventilation and drainage where necessary for protection.

JAR 25.61 1 Accessibility provisions

Means must be provided to allow inspection (including inspection of principal structural elements and control systems), replacement of parts normally requiring replacement, adjustment, and lubrication as necessary for continued airworthiness. The inspection means for each item must be practicable for the inspection interval for the item. Non-destructive inspection aids may be used to inspect structural elements where it is impracticable to provide means for direct visual inspection if it is shown that the inspection is effective and the inspection procedures are specified in the maintenance manual required by JAR 25.1529.

(a) Each removable bolt, screw, nut, pin or other removable fastener (see ACJ 25.607 (a)) must incorporate two separate locking devices if -

Its loss could preclude continued flight and landing within the design limitations of the aeroplane using normal pilot skill and strength; or

(1)

Reissued by Change 15 1 -D-I Change 12

JAR-25 SECTION 1

JAR 25.61 9 (continued)

JAR 25.613 Material strength properties and design values

(a) Material strength properties must be based on enough tests of material meeting approved specifications to establish design values on a statistical basis.

(b) Design values must be chosen to minimise the probability of structural failures due to material variability. Except as provided in sub- paragraph (e) of this paragraph, compliance with this sub-paragraph must be shown by selecting design values which assure material strength with the following probability:

Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99% probability with 95% confidence.

For redundant structure, in which the failure of individual elements would result in applied loads being safely distributed to other load carrying members, 90% probability with 95% confidence.

(c) The effects of temperature on allowable stresses used for design in an essential component or structure must be considered where thermal effects are significant under normal operating conditions.

(d) The strength, detail design, and fabrication of the structure must minimise the probability of disastrous fatigue failure, particularly at points of stress concentration.

Greater design values may be used if a ‘premium selection’ of the material is made in which a specimen of each individual item is tested before use to determine that the actual strength properties of that particular item will equal or exceed those used in design.

(1)

(2)

(e)

JAR 25.615 Reserved

JAR 25.619 Special factors

The factor of safety prescribed in JAR 25.303 must be multiplied by the highest pertinent special factor of safety prescribed in JAR 25.621 through JAR 25.625 for each part of the structure whose strength is -

(a) Uncertain.

(b) Likely to deteriorate in service before normal replacement; or

(c) Subject to appreciable variability because of uncertainties in manufacturing processes or inspection methods.

Where the Authority is not satisfied in a specific case that a special factor is the correct approach to ensuring the necessary integrity of the parts of the structure under service conditions, other appropriate measures must be taken.

JAR 25.621 Casting factors

The approved national standards of the participants are accepted by the Authorities as alternatives to FAR 25.62 I. 0 JAR 25.623 Bearing factors

Except as provided in sub-paragraph (b) of this paragraph, each part that has clearance (free fit), and that is subject to pounding or vibration, must have a bearing factor large enough to provide for the effects of normal relative motion.

No bearing factor need be used for a part for which any larger special factor is prescribed.

(a)

(b)

JAR 25.625 Fitting factors

For each fitting (a part or terminal used to join one structural member to another), the following

For each fitting whose strength is not proven by limit and ultimate load tests in which actual stress conditions are simulated in the fitting and surrounding structures, a fitting factor of at least 1-15 must be applied to each part of -

apply:

0 (a)

(1) The fitting;

(2)

(3)

(b) No fitting factor need be used - ( I ) For joints made under approved

practices and based on comprehensive test data (such as continuous joints in metal plating, welded joints, and scarf joints in wood); or

With respect to any bearing surface for which a larger special factor is used.

The means of attachment; and

The bearing on the joined members.

(2)

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SECTION 1

JAR 25.625 (continued)

JAR-25

JAR 25.629(b)(2) (continued)

(c) For each integral fitting, the part must be treated as a fitting up to the point at which the section properties become typical of the member.

(d) For each seat, berth, safety belt, and harness, the fitting factor specified in JAR 25.785(f)(3) applies.

JAR 25.629 Flutter, deformation, and failsafe criteria

(a) General. Compliance with this paragraph must be shown by calculations, resonance tests, or other tests found necessary by the Authority. Full scale flight flutter tests at speeds up to Vi&, for the critical aeroplane flutter modes must be conducted when -

Mo is equal to or greater than (1) 0.8 M;

(2) The adequacy of flutter analysis and wind tunnel tests have not been established by previous experience with aircraft having similar design features; or

(3) The conditions specified in sub- paragraph (a)(l) or (2) of this paragraph exist, and modifications to the type design have a significant effect on the critical flutter modes.

(b) Flutter and divergence prevention. The dynamic evaluation of the aeroplane must include an investigation of the significant elastic, inertia, and aerodynamic forces associated with the rotations and displacements of the plane of the propeller. In addition, the following apply:

The aeroplane must be designed to be free from flutter and divergence (unstable structural distortion due to aerodynamic loading) for all combinations of altitude and speed encompassed by the V&- versus altitude envelope enlarged at all points by an increase of 20% in equivalent air-speed at both constant Mach number and constant altitude, except that the envelope may be limited to a maximum Mach number of 1.0 when M D is less than 1.0 at all design altitudes a n d - s following is established:

(i) A proper margin of damping exists at all-speeds up to M,; and

(ii) There is no large and rapid reduction in damping as MD is approached.

(2) If concentrated balance weights are used on control surfaces, their effectiveness

(1)

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and strength, including supporting structure, must be substantiated.

(c) Loss of control due to structural deformation. The aeroplane must be designed to be free from control reversal and from undue loss of longitudinal, lateral, and directional stability and control, as a result of structural deformation (including that of the control surface covering) at speeds up to the speed prescribed in sub- paragraph (b) of this paragraph for flutter prevention.

safe criteria must be met: (d) Fail-safe criteria. The following fail-

It must be shown, by analysis or tests, that the aeroplane is free from such flutter or divergence that would preclude safe flight, at any speed up to VD, after each of the following:

si) Each of the failures, malfunctions, or adverse conditions listed in sub-paragraph (d)(4) of this paragraph.

(ii) Any other combination of failures, malfunctions, or adverse conditions not shown to be extremely improbable.

(2) If a failure, malfunction, or adverse condition described in sub-paragraph (d)(4) of this paragraph is simulated during a flight test in showing compliance with this paragraph, the maximum speed investigated need not exceed V if it is shown, by correlation of the flight -FFc test data with other test data or analyses, that hazardous flutter or divergence will not occur at any speed up to V,.

The structural failures described in sub-paragraphs (d)(4)(i) and (ii) of this paragraph need not be considered in showing compliance with this paragraph if engineering data substantiate that the probability of their occurrence is negligible by showing that the structural element is designed with -

(i) Conservative static strength margins for each ground and flight loading conditions specified in this JAR-25; or

(ii) Sufficient fatigue strength for the loading spectrum expected in operation.

(4) The failures, malfunctions, or adverse conditions used to show compliance with this paragraph are as follows:

(1)

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-- (3)

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JAR-25 SECTION 1

JAR 25.629(d) (continued)

(i) Failure of any single element of the structure supporting any engine, independently mounted propeller shaft, large auxiliary power unit, or large externally mounted aerodynamic body (such as an external fuel tank).

(ii) Any single failure of the engine structure, on turbo-propeller aeroplanes, that would reduce the yaw or pitch rigidity of the propeller rotational axis.

(iii) Absence of propeller aerodynamic forces resulting fiom the feathering of any single propeller, and, for aeroplanes with four or more engines, the feathering of the critical combination of two propellers. In addition, a n y single feathered propeller must be paired with the failures, specified in (d)(4)(i) of this sub-paragraph, involving failure of any single element of the structure supporting any engine or independently mounted propeller shaft, and the failures specified in (d)(4)(ii) of this sub-paragraph.

(iv) Any single propeller rotating at the highest likely overspeed.

(v) Failure of each principal structural element selected for compliance with JAR 25.571 (b). Safety following a failure may be substantiated by showing that losses in rigidity or changes in frequency, mode shape, or damping are within the parameter variations shown to be satisfactory in the flutter and divergence investigations.

(vi) Any single failure or mal- function, or combinations thereof, in the

-

flight control system considered under JAR 25.671, 25.672 and 25.1309, and any single failure in any flutter damper system. Investigation of forced structural vibration other than flutter, resulting from failures, malfunctions, or adverse conditions in the automatic flight control system may be limited to airspeed up to &: V

JAR 26.631 Bird strike damage

the velocity of the aeroplane (relative to the bird ~-

along the aeroplane’s flight path) is equal to V, at sea-level or 0.85 Vc at 8000 ft, whichever i s i G more critical. Compliance may be shown by analysis only when based on tests carried out on sufficiently representative structures of similar design. (See ACJ 25.631.)

CONTROL SURFACES

JAR 25.651 Proof of strength

(a) Limit load tests of control surfaces are required. These tests must include the horn or fitting to which the control system is attached.

(b) Compliance with the special factors requirements of JAR 25.619 to 25.625 and 25.657 for control surface hinges must be shown by analysis or individual load tests.

JAR 25.655 Installation

Movable tail surfaces must be installed so that there is no interference between any surfaces when one is held in its extreme position and the others are operated through their full angular movement.

If an adjustable stabiliser is used, it must have stops that will limit its range of travel to the maximum for which the aeroplane is shown to meet the trim requirements of JAR 25.161.

(a)

(b)

JAR 25.657 Hinges

(a) For control surface hinges, including ball, roller, and self-lubricated bearing hinges, the approved rating of the bearing may not be exceeded. For non-standard bearing hinge configurations, the rating must be established on the basis of experience or tests and, in the absence of a rational investigation, a factor of safety of not less than 6-67 must be used with respect to the ultimate bearing strength of the softest material used as a bearing.

Hinges must have enough strength and rigidity for loads parallel to the hinge line.

(b)

The aeroplane must be designed to assure capability of continued safe flight and landing of the aeroplane after impact with a 4 lb bird when

Change 8 143-4 Reissued by Change 15