Preliminary clues from the flight data recorder (FDR) recovered on 9 November from the Atlantic Ocean confirm US Air Force radar analysis of EgyptAir Flight 990's final seconds, including the Boeing 767-300ER's plunge from 33,000ft (10,000m).

More data will be required before investigators can explain the crash on 31 October off Nantucket Island which killed 217 passengers and crew.

Data from the 55-parameter FDR will be confirmed by a panel of FDR experts from the NTSB, US Federal Aviation Administration, Egypt, Boeing and Pratt & Whitney, says Jim Hall, chairman of the US National Transportation Safety Board (NTSB). At press time, the cockpit voice recorder (CVR) had not been recovered, but investigators hoped to trace it through locator signals. Flight 990's last routine communications were almost seven minutes before the aircraft's sudden dive.

USAF radar returns show that the aircraft dived at high speed in a straight line for around 40s until reaching 16,700ft, when it turned right and climbed back to 24,000ft before resuming its dive 37s later.

Preliminary data from the FDR initially shows an uneventful flight, cruising at 33,000ft, followed by the autopilot disconnecting. About 8s later the aircraft begins what appears to be a controlled high-speed descent to about 19,000ft. NTSB accident investigators "are still in the process of recovering data from the remaining 5s to 10s [of the flight]," says Hall. "The altitude profiles portrayed by the radar data and the FDR appear to be consistent," he adds.

Early FDR readouts do not provide any evidence that the thrust reverser system played a role in the accident. Further analysis of the FDR could indicate whether the dive was initiated by the crew or a result of a mechanical failure.

Source: Flight International