© COPYRIGHT, PROPRIETARY INFORMATION OF SMITHS AEROSPACE LTD AND SHAW AERO DEVICES A Practical Approach For Inerting Systems on Commercial Aircraft and.

© COPYRIGHT, PROPRIETARY INFORMATION OF SMITHS AEROSPACE LTD AND SHAW AERO DEVICES

A Practical Approach For Inerting Systems on Commercial Aircraft and the Development of Industry Standards

Presented by Phil Jones & Brian Greenawalt

Shaw Aero Devices

2


History of Recent Commercial Inerting

FAA proposed concepts for practical inerting of commercial aircraft fuel tanks

Storage of nitrogen enriched air in the ullage of the tank

Use of different flow modes in phases of flight

FAA proposed building of inerting system for 747SP

Team members from FTIHWG

Onboard ground inerting (OBGI) system

Designed for inerting fuel tank as well as cargo fire suppression

3


OBGI System Schematic

4


System Operation

Engine bleed air Pressurized air supply

Cooling air Reduce bleed air temperatures

Filter Remove contaminants found in bleed air

Heater Reheats air after run from heat exchanger to prevent condensation

Hollow fiber membrane Pressure device which reduces the oxygen level in air stream

Dual orifice valve Changes the back pressure on the hollow fiber membrane Different flow modes – high flow/low purity, low flow/high purity

Distribution system Injects nitrogen into tank

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747SP OBGI System (CATIA Model)

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Use of OBGI System

Converted to OBIGGS

Used as a flying test bed

Proved concepts Storage of nitrogen in fuel tank ullage Dual flow mode

Updating required for integration into commercial aircraft Pallet style design – space and weight restrictive


Installation

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Installation Location

FAA 747SP large installation area available

Installation location was central on the aircraft

Benign environment & easily accessible

Relatively few personnel involved and highly aware of program

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747SP OBGI System

View from forward looking aft and up

Items visible include OEA permeate bleed manifold, ASM inlets and

supporting structure

View from forward looking aft and up

Items visible include inlet door control cable, ASM outlets, supporting structure and NEA termination point

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Space availability is rare on smaller aircraft Large open bays not available

Proximity to the following systems: Pressurized air – bleed air Cooling air Fuel tank

Environmental conditions in location No all available locations are contained within bays and may be

exposed to elements or near high temperature components May be difficult for maintenance actions

Human safety NEA leakage into pressurized areas or adjacent bays

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System size must be minimized for use in most applications

Installation in close proximity to interface locations a benefit Less weight required for connections

Location should be chosen for installation environment and ease of maintenance should also be considered

Health and safety of passengers/crew and maintenance personnel must be considered Potential leak and accumulation of nitrogen gas


System Performance & Analysis

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Analysis Requirements

Flammability exposure model

Fuel tank thermal model

Inerting system performance model

Aircraft information required Configuration Systems performance Flight details

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System Performance

Aircraft configuration Ullage Volume Vent configuration Space availability Weight

Aircraft OBIGGS interface systems Bleed air pressure, temperature and flow profile Cooling air pressure, temperature and flow profile Maximum NEA flow Contaminants

Flight details Climb & descent rate Cruise altitude & duration

Other issues Allowable flammability exposure Reliability requirement Oxygen concentration

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Inerting Performance Model

Inerting performance model throughout flight profile Receives external aircraft inputs

Bleed air conditionsCooling air conditions

Uses performance of OBIGGSHeat exchangerFilterHollow fiber membraneDual orifice In-tank distribution

Calculates conditions within tankUllage spaceTemperaturePressure

Result of the model is O2% in the tankOxygen concentration in ullage space throughout flight profile

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Single Aisle Aircraft Performance Curve

Single Aisle Aircraft, Percentage of Oxygen in Ullage & Altitude

0

5

10

15

20

25

30

0 100

Time-Minutes

Par

tial

Pre

ssu

re-p

sia,

%O

2

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

Alt

itu

de

(ft)

CWT %O2( vol)

"12%"

Flight Profile

Case Details

Tank type

Init.Oxygen Level %

Fuel Oxygen Level % Initial Fuel Load %

CWT Landing Temp (F)

Tank Capacity(cu-ft)

Cruise Time (min)

ASM(s) Installed

12

21

CWT

0

-10

350

1

60

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Flammability Exposure Model

Reliability

Aircraft System Performance

(Bleed & cooling air, etc.)

OBIGGS Performance

(Ullage inert?)

Tank Conditions(Ullage & pressure)

Flight Details(Altitude,

temperature and flight profile)

Fuel tank thermal model

FlammabilityExposure

Model

Hollow Fiber Performance(NEA flow & purity)

Flammable

Conditions?

Inert?

Options:

Non-flammable & not inert

Non-flammable & inert

Flammable & inert

Flammable &not inert

Contributes to fleet wide flammability

No

No

No

Yes

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Flammability Exposure Model

Determines fleet average flammability exposure Total flammable time divided by the total operating time including

ground operations Flight profile randomly selected

Monitor inputs throughout flight profileTemperature & pressure conditions in tank – flammable?Tank ullage oxygen concentration – inert?

OBIGGS performance Producing required purity and flow of NEA Reliability – operating?

Flammable time during flight profile adds to fleet wide exposure Time flammable conditions exist and tank is not inert

Process is restarted until number of flights representative of fleet usage is reached

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System Performance & Analysis

Flammability exposure analysis

Fuel tank conditionsTemperaturePressureFuel vapor contentOxygen concentration

Inerting system performancePurity & flow rate of NEAReliability of inerting system

Total flammable time (when flammable and not inert) divided by the total operating time including ground operations


Modular Inerting System

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Current system Pallet system requires large installation area

Extra weightPallet-airframe mounting & component-pallet mountingPallet structure & component housingDucting runs between components Interstitial heater

Approach not acceptable for narrow body aircraft Space availabilityWeight penalty

New configuration required for each aircraft

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Modular inerting system Package all major components in one housing

Hollow fiber membraneFilterHeat exchanger

Individual housings & mountings not required

Modular housing replaces need for tubing runs between components

Close communication between heat exchanger and hollow fiber membrane removes need for interstitial heater

Same Shaw Aero patented “Module” interchangeable across aircraftSingle aisle requires 1 module, twin aisle requires 3 modulesSingle & twin aisle module interchangeable - Stock 1 module part number

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24



25



Reduced weight over distributed components

Removal of interstitial heater

Fits within space availability of smaller aircraft

One common designed component that is used across many aircraft


Health Monitoring

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Health Monitoring

System required to measure the health of the inerting system

Options include:

Measurement of O2 in-tank

Measurement of O2 from inerting system

Measurement of flow of NEA from inerting system

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Health Monitoring

Current oxygen sensors Test bed measurement of O2% in tank accomplished with FAA system

Sensors have a short lifeEquipment requires large space availability

Commercially available oxygen sensors cannot be placed in tankSensing elements superheat sample, that may contain fuel vapors

Measurement of O2% of NEA stream prior to tank infers tank O2%

Purity of NEA produced by inerting system

Should be used in conjunction with flow sensor

Tight measurement tolerances required

Failures in the following systems will not be detected

NEA distribution

Tank vent system

Previous flight assumed inert

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Health Monitoring

Non-oxygen sensing methods

Measure pressure or flow downstream of inerting systemLatent hollow fiber membrane failures not detected

Measure O2% of inerting system with GSE at lengthy intervals

Tank O2% should be measured

Tank O2 level measured directly by sampling a few times during the flight at critical tank location

Not inferred – total loop closure

Can we reduce the life cycle costs of the inerting system?

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Health Monitoring

Current sensing methods are:

Too large

Not compatible with environment

Flawed

Currently working on developing system that will measure the O2% in-tank


Industry Standards

32


Industry Standards

Industry standards are needed to define

System performance

System design

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Industry Standards

AIA Document Defines problem tanks Methods of defining flammability Sets flammability exposure limits

Fleet wide average levelsSpecial case of 80°F days

Methods of reducing flammabilityManaging heat transferDisplacing the flammable zoneUllage sweeping InertingFoam

Monte Carlo Analysis

Document submitted to FAA

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Industry Standards

SAE

Group made up of cross-section from two SAE groupsAE-5 Aerospace Fuel, Oil and Oxidizer SystemsAC-9 Aircraft Environmental Systems

Document encompases commercial and military aircraftBackground

Requirements

System Design

Validation & Verification

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Industry Standards

Background Lessons learned Gasses used Definition of inert

Requirements Types of aircraft Fuels Environmental conditions

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Industry Standards

System Design Architectures Air sources Distribution methods Tank types Performance Impact to and from other systems System Control and monitoring Analysis methods Installation RMTS

Validation & Verification

37


Industry Standards

AIA document submitted to FAA

SAE document currently in progress

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The Fourth Triennial The Fourth Triennial International Aircraft Fire and Cabin Safety International Aircraft Fire and Cabin Safety Research ConferenceResearch Conference

The Fourth Triennial The Fourth Triennial International Aircraft Fire and Cabin Safety International Aircraft Fire and Cabin Safety Research ConferenceResearch Conference

© COPYRIGHT, PROPRIETARY INFORMATION OF SMITHS AEROSPACE LTD AND SHAW AERO DEVICES A Practical Approach For Inerting Systems on Commercial Aircraft and.

Documents

tank slide

obgi system schematic

suppression slide

inerting fuel tank

bleed air heater

use of obgi system

inerting systems

weight restrictive slide