Practical Approach to Aircraft Inerting Systems Development

1. 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

5. 747SP OBGI System (CATIA Model)

6. 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

7. Installation

8. 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

9. 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

10. Installation Location • 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

11. Installation Location • 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

12. System Performance & Analysis

13. Analysis Requirements • Flammability exposure model • Fuel tank thermal model • Inerting system performance model • Aircraft information required • Configuration • Systems performance • Flight details

14. 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

15. Inerting Performance Model • Inerting performance model throughout flight profile • Receives external aircraft inputs • Bleed air conditions • Cooling air conditions • Uses performance of OBIGGS • Heat exchanger • Filter • Hollow fiber membrane • Dual orifice • In-tank distribution • Calculates conditions within tank • Ullage space • Temperature • Pressure • Result of the model is O2% in the tank • Oxygen concentration in ullage space throughout flight profile

16. Single Aisle Aircraft Performance Curve

17. Flammability Exposure Model Flammable Conditions? Inert? Contributes to fleet wide flammability No No No Yes Options: Non-flammable & not inert Non-flammable & inert Flammable & inert Flammable &not inert

18. 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 profile • Temperature & 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

19. System Performance & Analysis • Flammability exposure analysis • Fuel tank conditions • Temperature • Pressure • Fuel vapor content • Oxygen concentration • Inerting system performance • Purity & flow rate of NEA • Reliability of inerting system • Total flammable time (when flammable and not inert) divided by the total operating time including ground operations

20. Modular Inerting System

21. Modular Inerting System • Current system • Pallet system requires large installation area • Extra weight • Pallet-airframe mounting & component-pallet mounting • Pallet structure & component housing • Ducting runs between components • Interstitial heater • Approach not acceptable for narrow body aircraft • Space availability • Weight penalty • New configuration required for each aircraft

22. Modular Inerting System • Modular inerting system • Package all major components in one housing • Hollow fiber membrane • Filter • Heat 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 aircraft • Single aisle requires 1 module, twin aisle requires 3 modules • Single & twin aisle module interchangeable - Stock 1 module part number

23. Modular Inerting System

24. Modular Inerting System

25. Modular Inerting System • 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

26. Health Monitoring

27. 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

28. Health Monitoring • Current oxygen sensors • Test bed measurement of O2% in tank accomplished with FAA system • Sensors have a short life • Equipment requires large space availability • Commercially available oxygen sensors cannot be placed in tank • Sensing 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

29. Health Monitoring • Non-oxygen sensing methods • Measure pressure or flow downstream of inerting system • Latent 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?

30. 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

31. Industry Standards

32. Industry Standards • Industry standards are needed to define • System performance • System design

33. Industry Standards • AIA Document • Defines problem tanks • Methods of defining flammability • Sets flammability exposure limits • Fleet wide average levels • Special case of 80°F days • Methods of reducing flammability • Managing heat transfer • Displacing the flammable zone • Ullage sweeping • Inerting • Foam • Monte Carlo Analysis • Document submitted to FAA

34. Industry Standards • SAE • Group made up of cross-section from two SAE groups • AE-5 Aerospace Fuel, Oil and Oxidizer Systems • AC-9 Aircraft Environmental Systems • Document encompases commercial and military aircraft • Background • Requirements • System Design • Validation & Verification

35. Industry Standards • Background • Lessons learned • Gasses used • Definition of inert • Requirements • Types of aircraft • Fuels • Environmental conditions

36. 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

38. The Fourth Triennial International Aircraft Fire and Cabin Safety Research Conference The Fourth Triennial International Aircraft Fire and Cabin Safety Research Conference