Analysis of a boeing 747 aircraft fuel tank vent system

This monograph presents an analysis of a 747 aircraft fuel vent system. The system is comprised of several fuel tanks feeding into a single vent tube. The analysis consisted of formulating equations that govern the venting an d heating of the center tank. Flow losses along each section of the vent sy stem were applied to correct the ideal flow from the center fuel tank. Thes e equations were programmed for solution on a digital computer. Results wer e computed for a flight from Athens, Greece, to New York with a 5-hour dela y on the ground before taking off again from New York. The heating caused b y air conditioning and bleed air from the engines on the ground during the long delay caused vaporization of fuel and increased the density of the air -fuel vapor. The result was very sluggish venting and "choked" flow produci ng a significant overpressure, at 13,000 ft altitude, sufficient to fail so me component of the center tank. This was a precursor event leading to seri ous consequences. The analysis supports a hypothesis of overpressure as the cause of the Trans World Airlines Flight 800 accident and shows that heati ng caused by air conditioning contributed to the sequence of events.