SYMPOSIA PAPER Published: 01 January 1966

Spontaneous Ignition Testing for High Speed Aircraft


The hydraulic systems of supersonic aircraft which are designed to cruise at altitudes of approximately 70,000 ft must operate under conditions which impose severe physical and chemical stresses on the fluid. Appraisals of the thermal stability, the oxidative stability, the lubricity, the effect of close-tolerance moving parts, and the flammability of the fluid should be made before its pumpability is determined. Performance tests have been selected which permit a practical estimation of the five prerequisite factors, but the most complex and difficult evaluation is that of flammability.

Under precisely defined conditions, spontaneous ignition of a flammable fluid occurs in the presence of an oxidant only when the temperature is at or above that required to generate heat by oxidation at a rate which is greater than the rate of the dissipation of this heat to the surroundings. This temperature may or may not be the “spontaneous ignition temperature” as preflame of combustion usually occurs by reaction mechanisms which differ from those encountered in the flames themselves. However, ignition will not occur below this temperature, so in order to evaluate the hazard of a hydraulic fluid fire in high speed aircraft, measurements must be made in surroundings which closely approximate the actual environment and conditions in the airplane. Essentially, for aircraft now being developed, this entailed the fabrication of a small hot compartment of titanium alloy, using milled skins with typical stiffeners and fastenings, means for introducing precisely variable quantities of hot, atomized test fluids, controlling and measuring temperatures and pressures (“altitudes”), and also measuring pressure transients and ignition delays. The resulting apparatus, measurements and techniques are described and discussed.

Author Information

Hamilton, W.
Lockheed-California Company, Burbank, California
Holloway, R.
Lockheed-California Company, Burbank, California
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Developed by Committee: D02
Pages: 150–168
DOI: 10.1520/STP44660S
ISBN-EB: 978-0-8031-6018-7
ISBN-13: 978-0-8031-6172-6