because the lower air pressure makes the mixture richer. During a climb, the fuel will become more flammable. Also, oxygen dissolved in the fuel comes out of solution before other gases, causing oxygen enrichment of the ullage, which increases ignitability.3.1.2 FUEL FLAMMABILITY IN TWA 800NTSB researchers briefed investigators on preliminary test results that Jet A (the fuel type used by TWA800) fuel is far more flammable than aircraft manufacturers and operators had previously believed particularly when it is heated to high temperatures (McKenna, 15/12/97,P32). A spokesman from California Institute of Technology (CalTech) said his tests indicated that roughly 50F increase in the temperature of Jet A can drop the minimum temperature required to ignite its vapors by a factor of three.NTSB officials said flight tests conducted in July 1997 indicated that the temperature inside the center fuel tank of TWA 800 may have been as high as 128F. Earlier, safety board research had indicated that the temperature in the tank was less then 96F. The data collected from the flight test combined with the CalTech research, would seem to indicate that the risk of explosion in the tank was substantially higher than conventional industry thinking would indicate.Before the disastrous flight of TWA 800, all three air conditioning packs were operated on the ground for about 2 hours to generate heat beneath the CWT (Daschle, 1996, p4). In the flight tests, the fuel-air mixture in the CWT ullage was stabilised at a temperature below the LEL on the ground. However, as the aircraft climbed, the atmospheric pressure decreased (the LEL decreases with decreasing atmospheric pressure) reducing the LEL temperature and allowing an explosive fuel-air mixture to exist in the tank ullage. 3.2 ELECTRICAL COMPONENT FAILURESNTSB research has uncovered minor failures and degradations of electrical hardware that has led some participants in the accident investigation t...
