Limiting Oxygen Concentration (LOC) Work Update

1. Limiting Oxygen Concentration (LOC) Work Update Steve Summer Project Engineer Federal Aviation Administration Fire Safety Branch, AAR-440 International Aircraft Systems Fire Protection Working Group Atlantic City, NJ November 5 - 6, 2003 IASFPWG – Atlantic City, NJ

2. LOC Testing – Work Update • Technical Note consisting of all data except 400 cycle short tests published and placed on website (AR-02/79) • 400 cycle short spark energy has been measured and testing has been completed • Final report currently being put together IASFPWG – Atlantic City, NJ

3. Facilities – Pressure Chamber IASFPWG – Atlantic City, NJ

4. Facilities – Pressure Chamber • 353 ft3 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 – Atlantic City, NJ

5. Facilities - LOC Test Article • 9 ft3 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. • ¼-in. aluminum plate. • Foil diaphragm. • Spark gap. • 2 tungsten electrodes with controllable gap alignment and spacing IASFPWG – Atlantic City, NJ

6. Apparatus – LOC Testing IASFPWG – Atlantic City, NJ

7. Apparatus – LOC Testing IASFPWG – Atlantic City, NJ

8. Ullage Vapor Sampling IASFPWG – Atlantic City, NJ

9. LOC Testing Apparatus • Ignition Sources • 10 kV Oil burner transformer operating at ~30 mA 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 • 400 cycle, 120 V hard short to ground provided high energy/current, short duration spark • Energy Measurements • Voltage and current traces were taken using a HV and current probe at the spark gap connected to oscilloscope IASFPWG – Atlantic City, NJ

10. Test Program • JP-8 LOC Tests • Mass Loading ~ 4.5 kg/m3 • 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 • ¼-in. aluminum plate • Ignition = movement of plate • Foil diaphragm • Ignition = rupture of foil IASFPWG – Atlantic City, NJ

11. Test Program (cont.) • Tests conducted initially at all altitudes with long duration oil burner transformer arc (~0.5 J, 1 s) • 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) • 400 cycle, 120 V hard short to ground IASFPWG – Atlantic City, NJ

12. IASFPWG – Atlantic City, NJ

13. 400 Cycle Hard Short Tests IASFPWG – Atlantic City, NJ

14. Spark Energy Measurements Energy ~ 2.8 J Duration ~ .01 s Energy ~ 2.2 J Duration ~ .006 s Energy ~ 1.75 J Duration ~ .01 s IASFPWG – Atlantic City, NJ

15. 400 Cycle Short Test Results IASFPWG – Atlantic City, NJ

16. Summary • ~2 J spark from 400 cycle short did not cause a change in the LOC at sea level • Of all ignition sources used (oil burner arc, engine ignitor spark, hot surface, 400 cycle short), none have caused an ignition with ullage above 12% O2 • Testing is complete and final report will be published and available on website ASAP IASFPWG – Atlantic City, NJ