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Ground and Flight Testing of a Boeing 737 Center Wing Fuel Tank Inerted With Nitrogen-Enriched Air
WILLIAM J HUGHES TECHNICAL CENTER ATLANTIC CITY NJ
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A series of aircraft flight and ground tests were performed by the Federal Aviation Administration FAA and the Boeing Company to evaluate the effectiveness of ground-based inerting GBI as a means of reducing the flammability of fuel tanks in the commercial transport fleet. Boeing made available a model 737-700 for modification and testing. A nitrogen-enriched air NEA distribution manifold, designed, built, and installed by Boeing, allowed for deposit of the ground-based NEA into the center wing tank CWT. The fuel tank was instrumented with gas sample tubing and thermocouples to allow for a measurement of fuel tank inerting and heating during the testing. The FAA developed an in-flight gas-sampling system, integrated with eight oxygen analyzers, to continuously monitor the ullage oxygen concentration at eight different locations. Other data such as fuel load, air speed, altitude, and similar flight parameters were made available from the aircraft data bus. A series of ten tests were performed five flight, five ground under different ground and flight conditions to demonstrate the ability of GBI to reduce fuel tank flammability. The CWT was inerted with NEA to approximately 8 oxygen concentration by volume for each test. The aircraft condition was then set fuel load, wind condition, and flight condition, and the oxygen concentration in the CWT was continuously monitored. Results showed that, under quiescent conditions, the oxygen concentration in the fuel tank remained somewhat constant, keeping the CWT inert below 10 to 12 oxygen by volume for relatively long periods of time. However, due to the cross venting configuration of Boeing aircraft, certain wind conditions created cross venting within the CWT which allowed for significant increases in the oxygen concentration. Some flight conditions also contributed to cross venting and created high oxygen concentrations within the fuel tank.
APPROVED FOR PUBLIC RELEASE