Swissair 111, TWA 800, and Electromagnetic Interference

On the evening of July 17, 1996, TWA 800 fell into the ocean seven miles from the Long Island town of East Moriches. The plane had taken off from New York’s JFK Airport and had been bound for Paris, France. All 230 people on board died. The inquiry into the crash, the most expensive and (in its attention to the plane’s internal systems) the most rigorous inquiry in aviation history, has lasted for four years. A final hearing by the National Transportation Safety Board has been taking place on August 22 and 23, 2000, as this issue of The New York Review goes to press; neither the hearing nor the report that will follow it is expected (according to advance press reports) to “pinpoint” the cause of the crash. The full written report will become available to the public in several months.1

During the first year and a half of the inquiry, investigators from the National Transportation Safety Board and from the FBI concentrated on three matters: the possibility of a mechanical cause, the possibility of a bomb, and the possibility of a missile. In November of 1997, the FBI formally announced its conclusion that neither a bomb nor a missile had caused the accident (at this point, the FBI withdrew from the case). In December of 1997, the Safety Board—which had painstrakingly reconstructed most of the plane and scrutinized all of its internal systems—held a week-long public meeting reviewing the extensive, but inconclusive, evidence it had accumulated.

Investigators had long known that the plane’s central fuel tank exploded, but had at first been uncertain whether that explosion occurred early or late in the sequence of events that brought the plane down. By the time that the December 1997 public meeting took place, the Safety Board had long since concluded that the central fuel tank explosion was an early event in the catastrophe. What still remained was to find the source of the ignition, the cause of the explosion.

Between December of 1997 and August of 2000, the Safety Board continued its search for the ignition source. Included in its inquiry, and emphasized in the August hearings, was the possibility of a short-circuit or some other problem in the plane’s 150 miles of aging wiring. Also included in the inquiry was the possibility of an external ignition source, electromagnetic interference from one, or more than one, of the many military and civilian ships and planes that had been in the vicinity of TWA 800 and that, along with powerful civilian and military transmitters on land, might have produced an adverse electromagnetic environment. This second line of inquiry—electromagnetic interference from a source external to the plane’s own wiring (internal and external sources of ignition are not mutually exclusive:damaged wiring inside a plane can increase its vulnerability to external transmissions)—is the subject of the article that follows.

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In the past two years, the National Transportation Safety Board has taken steps to assess the severity of the electromagnetic environment that surrounded…


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