Study of the Flammability of Commercial Transport Airplane Wing Fuel Tanks

摘要

The Fire Safety Team of the Airport and Aircraft Safety Research and Development Division performed tests at the Federal Aviation Administration (FAA) William J. Hughes Technical Center using the environmental chamber and the air induction facility (wind tunnel) to examine individual effects that contribute to commercial transport wing fuel tank flammability. Additionally, previously acquired wing tank flammability measurements taken during flight tests were compared with the results from the FAA Fuel Air Ratio Calculator in an effort to see if the calculations agreed with existing flight test data. The results of the scale fuel tank testing in the environmental chamber showed that (1) fuel height in the tank had little or no effect on the flammability, (2) increasing the amount of heat on the top surface and a higher ambient temperature caused increased flammability, and (3) lower fuel flash point increased flammability greatly. Wind tunnel tests conducted with a section of a Boeing 727 wing tank showed that, under dynamic airflow conditions, change in ullage temperature was the primary mechanism affecting ullage flammability, not fuel temperature, as observed in environmental chamber tests. Other wind tunnel tests showed that the angle of attack of the fuel tank played little role in reducing fuel tank flammability, but that a cross-venting condition of the fuel tank would lead to a very rapid decrease in hydrocarbon concentration. An input temperature algorithm could be used with the FAA Fuel Air Ratio Calculator to significantly improve predictions of wing tank ullage flammability, based on tests that showed in-flight changes of ullage flammability in a wing tank are driven largely by the ullage temperature. This is very different from what had been shown with a center wing fuel tank, in which fuel temperature continues to be the main driver of flammability even during flight.