1. Presented by Phil Jones & Brian Greenawalt 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 Cooling air Filter Heater
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
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
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 Requirements Lessons learned Gasses used
Definition of inert
Requirements
Types of aircraft
Fuels
Environmental conditions

36. Industry Standards System Design Validation & Verification
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