Analysis of Aircraft Fuel Tank Fire and Explosion Hazards

Under simulated flight environments, fuel/air ratios at various locations of the ullage space were determined using in-line gas chromatograph measurement. Using the shallow tank experimental data showed that during ascent and cruise portion of the flight profile, uniform fuel/air mixtures were found to exist within the entire ullage volume. Significant fuel/air gradients existed during the descent portion of the flight profile, with mainly air near the vent inlet. Evaporation lag was observed during ascent and level flight when liquid Jet A fuel was maintained at 80 degree F. When the liquid fuel temperature was increased to 120F, evaporation rate was found to be rapid enough that the evaporative lag phenomena was no longer observed. By vibrating the fuel tank, it greatly increased the rate of off-gassing of dissolved air in the liquid fuel. This in turn significantly changed the fuel/air ratio in the ullage space. Two separate and complementary models were developed to predict fuel/air concentrations within the ullage.