SUMMARY OF HEARING: Wednesday, December 10, 1997

An NTSB Board of Inquiry investigating what touched off the explosion that downed TWA flight 800 heard testimony from a geologist, an investigator into the use of explosives against aircraft and experts on aircraft systems. Their testimony indicated that a meteorite strike was highly improbable and there was no evidence of the use of explosives. Further, of the many possible internal sources of the ignition in the center fuel tank, four were now being given close attention.

Dr. William Cassidy, professor of Geology and Planetary Science at the University of Pittsburgh, said his mathematical calculations, based on past recorded hits on dwellings and cars, indicated that the chance of a meteorite striking an aircraft is roughly once in every 59,000 to 77,000 years. And, he said, an impact of the force needed to destroy a jumbo jet was even more unlikely.

Bob Swaim, an NTSB aircraft systems investigator, said many possible internal ignition sources have been set aside for the time being, and that four were now being given close scrutiny. These included short circuits and damaged wiring for the system used to monitor the fuel in the plane’s center fuel tank.

The hearing resumes Thursday with a panel devoted to the issues of aging aircraft.