PANEL SUMMARY: Investigation of Recorded Data

According to the testimony of John Clark, deputy director of the NTSB’s Office of Research and Engineering, three types of recorded data were used in the investigation: radar, cockpit voice recorder (CVR) and flight data recorder (FDR). Taken together, these data show that TWA 800 was climbing, in wings-level flight when the explosion occurred. Aircraft parts in and around the center wing tank separated and fell first. The portion of the fuselage forward of the wings then detached and fell. The remainder of the aircraft rolled to the left and continued to climb. It then rolled inverted to the right, pointing down, and plunged toward the ocean.

Location of Flight 800 (72K)

TWA 800 was tracked by radar throughout its short flight, and Clark identified the radar installations that tracked it. These included airport surveillance radars (ASR) in and around the New York City and Long Island areas and air route traffic control centers (ARTCCs) at Boston, New York and Washington, DC. The NTSB received magnetic tapes from the FAA, collected from these sites, by the morning after the accident.

Radar Data (88K)
Primary radar returns show simply the reflection of the radar off the side of the aircraft. Secondary returns, transmitted by the aircraft’s transponder, are triggered by the action of the radar signal on the transponder. In addition to location, they show aircraft altitude and identification. A compilation of radar returns for TWA 800 shows primary and secondary data for the flight before the explosion and primary returns alone for the aircraft pieces and wreckage afterwards.

Clark showed how these data were correlated with the location of wreckage on the ocean floor. When each piece of wreckage was brought to the surface, its resting place had been recorded, using the satellite-based Global Positioning System (GPS) and other tools. NTSB investigators then conducted trajectory studies of numerous pieces of wreckage. They based these studies on the location each piece had held in the aircraft before the explosion, on wind data and on the known behavior of pieces of various weights and densities as they fall.

The result was demonstration of a three-stage sequence: First the explosion, releasing wreckage from in and around the center fuel tank, which came to rest in a debris field designated the red zone. Next the separation of the forward fuselage, whose wreckage was found in the zone known as yellow. Finally, the continuing flight and eventual breakup and descent of the remainder of the aircraft, in the green zone.

Clark said the FDR, which recorded 18 aspects of the flight, such as altitude and heading, indicated nothing out of the ordinary until it ceased recording, in a manner attributed to power loss at the time of the explosion. The CVR also showed no anomalies until the last fraction of a second before power loss terminated its operation as well. During that last moment, the device captured a high-energy signal that was consistent with an explosion in the fuel tank, whose sound was transmitted to the cockpit area microphone through the aircraft structure.