Crashed Turkish airline was on autopilot

The Turkish Airlines Boeing 737 that crashed at Amsterdam’s Schiphol airport last week, killing nine, was running on autopilot and stalled because a faulty altimeter prompted the plane to cut power to its engines, Dutch safety officials said on Wednesday.

The initial findings have prompted the Dutch Safety Board to issue a warning to Boeing to prevent faulty radio altimeters influencing the autopilot. But they also raised questions about the role of the pilots, who were among those killed.

Pieter van Vollenhoven, chairman of the safety board, said the use of autopilot when descending to land was common practice at Turkish Airlines although policies varied between carriers.

Data from the black box flight recorder showed that the left-hand of two radio altimeters that are used for precise altitude measurements when landing gave an erroneous reading of the plane’s height, telling the autopilot the plane was 8ft below sea level rather than 1,950ft above.

“This sudden change in altitude had a direct effect on the automatic throttle which controls engine power during the descent,” Mr van Vollenhoven told a news conference. “The aircraft reacted as if it was at a height of just a few metres above the runway by fully cutting engine power.”

The erroneous altitude reading triggered an automatic warning telling the pilots to deploy the plane’s undercarriage. The plane also lost speed. But the crew ignored both the warning and the loss of airspeed, Mr van Vollenhoven said.

Only when the control stick started to vibrate to signal that the plane had slowed to stalling speed did the pilots react by applying full power, by which time the plane was at 450ft.

“However this was too late for the plane to regain flight,” Mr van Vollenhoven said.

The black box, which had data from eight previous flights recorded on it, showed that the same error with the altimeter had occurred at least twice already.

Boeing has been asked to change the manual for Boeing 737s to forbid the use of autopilot and the automatic throttle during descent and landing if there is an error in the radio altimeters, Mr van Vollenhoven said. Boeing was also urged to investigate whether the same should apply during normal flight.

The safety board had found no other evidence of problems with the aircraft or irregularities during the flight, he said.

As well as the three pilots in the cockpit, one other crew member and five passengers were killed when the plane crashed one kilometre from the runway.

Turkish Airlines’ last fatal crash was in January 2003, when a domestic flight came down in fog when attempting to land at Diyarbakir, a city in the south-east of Turkey. It was the first fatal air accident at Schiphol since 1994.