Investigation of Aircraft Void Space Fuel Fire Phenomena

This program was conducted to determine the effects of various system and environmental parameters on the ignition and sustainment of 0.50 cal API projectile induced void space fires. The void space consisted of a 4-inch thick area adjacent to a 20 gallon JP-4 filled fuel tank. In-flight aircraft simulation was accomplished by discharging compressed air over the test specimen moldline skin. Simulated sea level aircraft velocities of 100, 240, and 400 knots were provided. Sustained void space fires were successfully obtained in approximately one fifth of the gun fire tests, however, because of the limited number of repeat tests at any given sustained fire condition, statistical data for repeatability was not generated. The parameters that were tested which influence the combustion in aircraft void spaces include: void space width, skin material types, fuel tank pressure, fuel tank damage configuration, fuel temperature, threat size/attitude/velocity, The environmental parameters are: external airflow velocity/temperature, external airflow boundary condition (laminar or turbulent), internal airflow rate/temperature. The results indicated that the specimen configuration, and test conditions before and after the projectile impact must be integrated in order to define and quantify the variables and their degree of importance to sustaining void space fires under aircraft inflight conditions and small arms threats. (Author)