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Dual Flow Inerting System: Enhancing Aviation Safety Through Reduced Flammability

Learn about FAA's development of the Dual Flow Inerting System to prevent tank explosions caused by high flammability, improving aircraft safety and fuel system design. Discover the benefits, applications, and ongoing progress of this innovative technology.

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Dual Flow Inerting System: Enhancing Aviation Safety Through Reduced Flammability

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  1. FAA R&D Dual Flow Inerting System Ivor Thomas Chief Scientific and Technical Advisor to the FAA, Fuel System Design Oct 30th, 2002 ivor.thomas@faa.gov

  2. Why Reduced Flammability? • Some tanks on some airplanes heated by nearby systems, • These tanks are the ones involved with last three accidents • FAA considers that tank safety level required needs both improved ignition prevention AND reduced flammability

  3. ARAC FTIHWG • Industry Study group established in 2000 • To examine inerting systems and make recommendations to FAA on future rule making • Examine various means of supplying inert gas • Develop cost and operational data

  4. ARAC FTIHWG Report • Inerting not practical because: • No Bleed Air Available • No Power to run needed compressor • Complicated distribution system in tank • Unreliable • Expensive • FAA should continue inerting studies

  5. FAA Work Since ARAC Report • Established Bleed Air was available in needed quantities but at lower pressures that thought needed for Air Separation Technology • Flow needed for Inerting System approximately 1 to 2 % of bleed flow available • Pressure adequate for most cases, descent still corner design point

  6. FAA Work Since ARAC Report • Testing to establish O2 level needed for inerting system • Adequate inerting obtained with approximately 12% O2 versus 9-10% previously thought needed

  7. FAA Work Since ARAC Report • Performance Analysis and subsequent testing showed Air Separation Technology would work at low pressures, 10 to 40 psig versus 50 to 100 psig used commercially

  8. ASM (Air Separation Module)

  9. Recent Significant Progress • 747 scale model and actual airplane test • Showed that complex distribution manifold in tank not needed • Simple single line into one bay was much more efficient than complex manifold

  10. Recent Significant Progress • Scale Model Testing • Tests using a ¼ scale model have been shown to be very cost effective and highly representative of the full scale airplane. • Scale model tests have confirmed simple distribution system efficacy • Scale model being used for climb/dive tests of system

  11. Variable flow inerting concepts • With the results of the bleed system and ASM performance, FAA developed several concepts of inerting all centered on sizing the system so the tank would be inert at touch down, but allowing the tank to breath in air in the early part of the descent

  12. Dual Flow Inerting System • Use of low flow high purity mode in climb and cruise coupled with a high flow, low purity mode for descent provides virtually full time inerting, without running on the ground. • Simple system eliminates compressor, cooling fan, only moving parts are shutoff valves and a temperature regulator

  13. Existing Cooling Inlet Check/Shutoff Valve Center Wing Tank Cooling Air, Flow reverses on Ground Shut Off Valve Temp control valve NEA Flow Heater Filter High and Low Flow Orifices (In common valve) ASM Heat Exchanger Waste Flow (O2 rich) Low flow, High Purity NEA for Ground, Climb and Cruise, High Flow, Low Purity NEA for Descent Existing Bleed Line Overboard Exit Simple Full-Time Inerting System

  14. Dual Orifice, Long flight- 200 minutes cruise duration Peak due to fuel burn on TO and early climb

  15. Initial Conclusions • Benefits of this approach: • Very Simple system, no compressor • No ground running needed • High reliability; Only moving parts are cooling flow modulating valve, plus shut off valves, plus flow controller (Regulator or two position orifice) • Low weight 50 lb + manifold to tank (737/A320 size Center Tank) • Minimum impact on airplane

  16. Descent Take-Off Climb Cruise

  17. Work In progress • Working with Boeing to develop flight test of the dual flow system in the winter of 2002/2003 • Working with Other OEM’s on application of concept to other airplanes. • New Spot Amendment to SFAR 88 allows the use of inerting as part of an alternate means of compliance

  18. Summary • Simple Dual Flow Inerting System shows great potential for use in commercial airplanes.

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