Ground-Based Inerting of a Boeing 737 Center Wing Fuel Tank

Abstract

A series of aircraft flight and ground tests were performed by the Federal Aviation Administration and the Boeing Company to evaluate the effectiveness of ground-based inerting (GBI) as a means of reducing the flammability of center wing fuel tanks (CWTs) in the commercial transport fleet. Boeing made available a Boeing 737-800 for modification and testing. The fuel tank was instrumented with gas sample tubing and thermocouples and tests were performed inerting the CWT to 8 percent oxygen to allow for a measurement of fuel tank inerting and heating. Results showed that under quiescent conditions the oxygen concentration in the fuel tank remained somewhat constant, keeping the CWT inert (below 10- to 12-percent oxygen by volume) for relatively long periods of time. Certain wind conditions and flight conditions created cross venting within the CWT that allowed for significant increases in the oxygen. A modification to the vent system created a significant increase in the benefit of the GBI even at low to moderate fuel loads.