The limiting surface temperature for spontaneous ingnition of fuel vapour/air mixtures in high speed aircraft

Abstract

Whereas in the past the temperature of aircraft tank walls or structures enclosing fuel or vapour have been well below the spontanecus ignition temperature, as aircraft speeds approach Mach 3 this is no langer the case, and it becomes essential to know with certainty what are the risks of ignition. In this Note the critical spontaneous ignition temperature as determined by several authorities for conditions of varying altitude and mixture movement are set out in an attempt to enable designers to estimate and minimise the ignition risks. Although there is considerable disagreement between certain authorities, it looks as if an increase in the permissible wall temperature (above 200°C) may be possible at high altitudes, because of the reduced pressure of the atmosphere. There seems to be a useful easement when mixture movement is present, and there is likely to be some due to partial heating of the surface, but more research on these aspects is required. Also there seems some prospects of developing fuel additives which will raise the temperature.