Flight-Testing of the FAA Onboard Inert Gas Generation System on ...

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LIST OF ACRONYMS ASM Air separation module CWT Center wing tank <strong>FAA</strong> Federal Aviation Administration HFM Hollow-fiber membrane NEA Nitrogen-enriched air OBIGGS <strong>Onboard</strong> inert gas generation system OBOAS <strong>Onboard</strong> oxygen analysis system OEA Oxygen-enriched air SCFM Standard cubic feet per minute SOV Shut<strong>of</strong>f valve t Metric ton viii
EXECUTIVE SUMMARY Significant emphasis has been placed on fuel tank safety since <strong>the</strong> TWA flight 800 accident in July 1996. Extensive development and analysis has illustrated that fuel tank inerting could potentially be cost-effective if air separation modules (ASM), based on hollow-fiber membrane technology, could be used in an efficient way. To illustrate this, <strong>the</strong> Federal Aviation Administration (<strong>FAA</strong>), with <strong>the</strong> assistance <strong>of</strong> several aviation-oriented companies, developed an onboard inert gas generation system with ASMs that uses aircraft bleed air to generate nitrogenenriched air at varying flow and purity (oxygen concentration) during a commercial airplane flight cycle. The <strong>FAA</strong> performed a series <strong>of</strong> ground and flight tests designed to prove <strong>the</strong> simplified inerting concept that is being proposed by <strong>the</strong> <strong>FAA</strong>. The <strong>FAA</strong>-developed system was mounted in <strong>the</strong> cargo bay <strong>of</strong> an A320 operated by Airbus for <strong>the</strong> purposes <strong>of</strong> research and development and used to inert <strong>the</strong> aircraft center wing fuel tank during testing. The system and center wing fuel tank were instrumented to allow for <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> system performance as well as inerting capability. The <strong>FAA</strong> onboard oxygen analysis system was used to measure <strong>the</strong> oxygen concentration in <strong>the</strong> center wing tank continuously during operation <strong>of</strong> <strong>the</strong> inerting system. The results <strong>of</strong> <strong>the</strong> tests indicated that <strong>the</strong> concept <strong>of</strong> <strong>the</strong> simplified inerting system is valid and that <strong>the</strong> air separation module dynamic characteristics were as expected for <strong>the</strong> limited test plan performed. Both one- and two-ASM configuration tests gave <strong>the</strong> expected performance with ASM pressure having <strong>the</strong> expected effect on flow rate and <strong>the</strong> duel-flow performance being predictable. Bleed air consumption was greater than expected during <strong>the</strong> cruise phase <strong>of</strong> flight. Additional research is needed to determine what changes in system design or operational methodology would best reduce <strong>the</strong> bleed airflow and <strong>the</strong> associated cost. The fuel tank inerting results illustrated that, as expected, no stratification or heterogeneous oxygen concentrations occurred in <strong>the</strong> tank for <strong>the</strong> inerting tests performed, in part due to <strong>the</strong> essentially rectangular box configuration <strong>of</strong> <strong>the</strong> tank, allowing easy distribution <strong>of</strong> <strong>the</strong> inert gas. A simple analytical model <strong>of</strong> <strong>the</strong> inerting process illustrated good agreement with <strong>the</strong> measured data. The measured effect <strong>of</strong> <strong>the</strong> high-flow mode was significant, allowing <strong>the</strong> single-membrane configuration to maintain an inert ullage (less <strong>the</strong>n 12%) during <strong>the</strong> entire flight cycle, even with <strong>the</strong> very high rate <strong>of</strong> descent employed for <strong>the</strong> flight-tests. When <strong>the</strong> high-flow mode was not used, <strong>the</strong> ullage reached a peak <strong>of</strong> 15% oxygen by volume. Fuel had virtually no effect on <strong>the</strong> resulting oxygen concentrations observed in all <strong>the</strong> tests. ix/x
Page 1 and 2: DOT/FAA/AR-03/58 O
Page 3 and 4: 1. Report No. DOT/FAA</stro
Page 5 and 6: TABLE OF CONTENTS EXECUTIVE SUMMARY
Page 7: 10 Correlation of
Page 11 and 12: Other previous stu
Page 13 and 14: 2.1.2.1 Center Wing Tank. The CWT <
Page 15 and 16: 2.2 TEST PROCEDURES. All tests were
Page 17 and 18: After passing through the</
Page 19 and 20: amount of flow (10
Page 21 and 22: 5. DISCUSSION OF RESULTS. The resul
Page 23 and 24: of the</st
Page 25 and 26: Figure 12 gives the</strong
Page 27 and 28: 5.2 FUEL TANK INERTING. The fuel ta
Page 29 and 30: the ullage would b
Page 31 and 32: Oxygen Concentration (% vol) 25 20
Page 33 and 34: 6. “A Review of
Page 35 and 36: Interface Description: Interface 1:
Page 37 and 38: APPENDIX C—THE FAA</stron
Page 39: APPENDIX D—CALCULATION OF BLEED A

Flight-Testing of the FAA Onboard Inert Gas Generation System on ...

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