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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. LOC Testing – Work Update.

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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


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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


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Facilities – Pressure Chamber

IASFPWG – Atlantic City, NJ


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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


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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


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Apparatus – LOC Testing

IASFPWG – Atlantic City, NJ


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Apparatus – LOC Testing

IASFPWG – Atlantic City, NJ


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Ullage Vapor Sampling

IASFPWG – Atlantic City, NJ


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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


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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


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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



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400 Cycle Hard Short Tests

IASFPWG – Atlantic City, NJ


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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


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400 Cycle Short Test Results

IASFPWG – Atlantic City, NJ


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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


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