Crashed 707 stalled as it attempted return to Sharjah

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Investigators have determined that a Sudanese Boeing 707-330C freighter stalled and crashed on departure from Sharjah after the crew overbanked the jet following a perceived engine failure.

Operated by Azza Air Transport the aircraft lifted off from runway 30 for a service to Khartoum but reached only about 300ft in height when the cowls of the starboard outboard engine detached.

Their separation severed a flex line supplying the engine pressure ratio indicators for the Pratt & Whitney JT3D powerplant.

With no insight into the true nature of the damage, the inquiry states, the crew would "most likely" have interpreted the cockpit indications, incorrectly, as an engine failure.

Flight 2241's first officer contacted Sharjah control tower and said the aircraft would return to the airport, after "losing number four engine".

It began to bank to the right. With the 707's flaps set at take-off position, the procedure required the bank angle to be limited to 15° until the aircraft reached an airspeed 10kt above climb-out velocity.

But the inquiry states that the pilots initiated a "sharp turn" that took the aircraft beyond this bank limit, despite its not reaching the airspeed threshold.

"It appears that engine thrust was not added simultaneously to compensate for the increased drag," says the United Arab Emirates General Civil Aviation Authority in its report into the 21 October 2009 crash. The aircraft, as a result, began to lose height.

While the pilot appears to have tried recovering - by a sudden increase in thrust - a nose-up command "probably pulled the aircraft into an accelerated stall", says the inquiry. This caused the right wing to drop further, and the 707 rolled steeply into a 90° right bank, diving into the ground.

Neither flight recorder provided any useful data, and the inquiry could not determine the precise performance of the aircraft. Limited radar data indicated that the 707 reached only 380ft, travelling at 149kt ground speed, before the fatal descent, which was captured by an airport surveillance camera. None of the six occupants survived.

Wreckage analysis ruled out accidental thrust-reverser deployment and investigators found no evidence that the engine involved had lost power.

But the inquiry discovered that the 40-year old jet (ST-AKW) had been poorly maintained. The cowls on the affected engine exhibited repairs that were "not to the quality of aviation standards", it says, and these poor repairs were "not unique" to the cowls. It concludes that the cowls were not properly latched before take-off, with the result that they were twisted and torn off as the 707 climbed away.