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This paper describes research performed to determine the ignition hazard presented by small fragments of superfine steel wool that may contact energized direct current wires in aircraft fuel tanks. Several different methods of shorting a circuit with steel wool were explored. An ignitable mixture of hydrogen, oxygen, and argon, calibrated to have a minimum ignition energy of 200 microjoules, was used as an ignition detection technique. The electrical currents at the ignition threshold were recorded to determine safe maximum allowable current limits for fuel tank electronics. The lowest current found to ignite the flammable mixture was 99 milliamps (mA); the lowest current found to ignite a steel wool wad in air only was 45 mA.

This study has been performed to aid in the effort to minimize the possibility of a fuel tank explosion in a commercial aircraft. An understanding of the mechanisms behind fuel vaporization processes in an aircraft fuel tank is essential to developing accident prevention techniques. An experiment was designed to measure the conditions existing within a heated aluminum fuel tank, partially filled with JP-8 jet fuel, under varying ambient conditions similar to those encountered by an in-flight aircraft. Comprehensive fuel tank data, including all temperatures, pressure, and ullage hydrocarbon concentration, was obtained during testing, and is available for use to validate heat and mass transfer calculations.