Limiting Oxygen Concentration LOC Work Update Steve Summer

Limiting Oxygen Concentration (LOC) Work Update Steve Summer Project Engineer Federal Aviation Administration Fire Safety Branch, AAR-440 IASFPWG – Ottawa, Canada International Aircraft Systems Fire Protection Working Group Ottawa, Canada July 8 - 9, 2003 07 -08 -03

LOC Testing – Work Update Ø Conducted sea level (SL) testing with a J-57 engine igniter Ø Conducted SL testing with a short duration arc from oil burner transformer Ø Measured voltage/current at spark gap and calculated energy for both spark/arc generator Ø Composed report of all data generated to date with the various ignition sources (AR-02/79)—due out shortly IASFPWG – Ottawa, Canada 07 -08 -03

Facilities – Pressure Chamber IASFPWG – Ottawa, Canada 07 -08 -03

Facilities – Pressure Chamber Ø 353 ft 3 pressure vessel • Working pressure of 650 psi. • Attached vacuum pump used to evacuate chamber to reduced pressures seen at altitude. • Not capable of simulating temperatures seen at altitude. IASFPWG – Ottawa, Canada 07 -08 -03

Facilities - LOC Test Article Ø 9 ft 3 simulated fuel tank placed inside of vessel equipped with: • Bottom surface heaters. • 12 thermocouples. • 2 piezoresistive pressure transducers mounted behind sintered porous metal discs. • Interchangeable pressure relief mechanism. F¼-in. aluminum plate. FFoil diaphragm. • Spark gap. F 2 tungsten electrodes with controllable gap alignment and spacing IASFPWG – Ottawa, Canada 07 -08 -03

Apparatus – LOC Testing IASFPWG – Ottawa, Canada 07 -08 -03

Apparatus – LOC Testing IASFPWG – Ottawa, Canada 07 -08 -03

Ullage Vapor Sampling IASFPWG – Ottawa, Canada 07 -08 -03

LOC Testing Apparatus Ø Ignition Sources • 10 k. V Oil burner transformer operating at ~30 m. A provided both long (~1 second) and short (~0. 1 second) arcs • J-57 Engine spark igniter provided a very short (~175 msecond) spark • 3" x 6" x 1" metal block heated by two cartridge heaters to temperature in excess of 1400°F Ø Energy Measurements • Voltage and current traces were taken using a HV and current probe at the spark gap connected to oscilloscope IASFPWG – Ottawa, Canada 07 -08 -03

Oil Burner Transformer Voltage & Current Traces IASFPWG – Ottawa, Canada 07 -08 -03

Test Program Ø JP-8 LOC Tests • Mass Loading ~ 4. 5 kg/m 3 • Ambient pressure corresponding to altitudes of 0, 10, 20, 30 and 38 kft • Ullage oxygen concentrations ranging from 21% to below the determined LOC • Tests conducted with two different pressure relief mechanisms F¼-in. aluminum plate – Ignition = movement of plate FFoil diaphragm – Ignition = rupture of foil IASFPWG – Ottawa, Canada 07 -08 -03

Test Program (cont. ) Ø Tests conducted initially at all altitudes with long duration oil burner transformer arc (~0. 5 J, 1 s) Ø Subsequent tests conducted with various ignition sources at sea level in effort to determine any variation of LOC with ignition source • Short duration oil burner transformer arc (~0. 08 J, 0. 1 s) • J-57 Engine igniter spark (~0. 5 J, 175 ms) • Hot surface vapor ignition (HSVI) IASFPWG – Ottawa, Canada 07 -08 -03

LONG DURATION OIL BURNER TRANSFORMER ARC TEST RESULTS IASFPWG – Ottawa, Canada 07 -08 -03

Aluminum Plate Relief Mechanism IASFPWG – Ottawa, Canada 07 -08 -03

Foil Diaphragm Relief Mechanism IASFPWG – Ottawa, Canada 07 -08 -03

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J-57 ENGINE SPARK IGNITER TEST RESULTS IASFPWG – Ottawa, Canada 07 -08 -03

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SHORT DURATION OIL BURNER TRANSFORMER ARC TEST RESULTS IASFPWG – Ottawa, Canada 07 -08 -03

Short Duration Test Results IASFPWG – Ottawa, Canada 07 -08 -03

HOT SURFACE VAPOR IGNITION TESTING (HSVI) IASFPWG – Ottawa, Canada 07 -08 -03

HSVI Testing Ø Test Setup • Setup was identical to the spark/arc ignition testing. • In place of spark, a 3" x 6" x 1" metal block was heated by two cartridge heaters for use as the ignition source. • Conducted only at sea level conditions. IASFPWG – Ottawa, Canada 07 -08 -03

HSVI Test Results Ø At 21% O 2, ignition was achieved at a hot surface temperature (HST) of approximately 1350ºF. Ø A half-dozen other tests were conducted at O 2 concentrations ranging from ~11. 5 – 14%. • Though some “puffs” of smoke could be seen as the HST approached ~1200º F, no ignitions occurred. Ø Therefore, HSI within the fuel tank provides no more of a threat than spark ignition. IASFPWG – Ottawa, Canada 07 -08 -03

Conclusions Ø LOC at SL through 10 kft is ~12%, increasing linearly through 40 kft to ~14. 5% Ø Little effect seen on SL LOC due to ignition source • • Long duration arc: 12% High powered spark: 12. 3% Short duration arc: 12. 9% HSVI: ? ? IASFPWG – Ottawa, Canada 07 -08 -03

Future LOC Work Ø Currently working with a very high energy spark (>20 J) • 120 Vac, 400 cycle hard short to ground • Will be placing in the tank within the next week. • To commence testing shortly thereafter. Ø Technote AR-02/79 due out shortly IASFPWG – Ottawa, Canada 07 -08 -03