Tests to Determine the Ullage Explosion Tolerance of Helicopter Fuel Tanks
ARMY RESEARCH AND TECHNOLOGY LABS FORT EUSTIS VA APPLIED TECHNOLOGY LAB
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Twenty-one ballistic tests were conducted on fuel tanks similar to those on US Army helicopters to determine their ability to withstand pressures generated during an ullage explosion. The tanks were filled with known JP-4air gas mixtures and impacted with caliber .30 M1 incendiary projectiles at approximately 2000 feet per second. The pressure rise was measured with transducers and the tank reponse was recorded with high-speed photography. The results indicated that noncrashworthy bladder tanks in honeycomb structure have an overpressure threshold of about 20 psig, while crashworthy tanks in Z-bar reinforced aluminum structure can tolerate explosive pressure to about 60 psig. The results can be useful in the design of optimum ullage protection schemes for the armor piercing incendiary API combat threat.