# Presentation: 423826

## Limiting Oxygen Concentration (LOC) Work Update

- International Aircraft Systems Fire Protection Working Group
- Atlantic City, NJ
- November 5 - 6, 2003

- Steve Summer
- Project Engineer
- Federal Aviation Administration
- Fire Safety Branch, AAR-440

## 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

## Facilities – Pressure Chamber

## 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.

## 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.
- 1⁄4-in. aluminum plate.
- Foil diaphragm.
- Spark gap.
- 2 tungsten electrodes with controllable gap alignment and spacing

## Apparatus – LOC Testing

## Apparatus – LOC Testing

## Ullage Vapor Sampling

## 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 second) 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

## 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
- 1⁄4-in. aluminum plate
-  Ignition = movement of plate
- Foil diaphragm
- Ignition = rupture of foil

## 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 s)
- Hot surface vapor ignition (HSVI)
- 400 cycle, 120 V hard short to ground

## Slide 12

## 400 Cycle Hard Short Tests

**400 Cycle Hard Short Tests**

## Spark Energy Measurements

**Energy ~ 2.2 J**
**Duration ~ .006 s**

**Energy ~ 2.8 J**
**Duration ~ .01 s**

**Energy ~ 1.75 J**
**Duration ~ .01 s**

## 400 Cycle Short Test Results

**400 Cycle Short Test Results**

## 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