The engines then cut out because a faulty altimeter prompted the plane to cut power to its engines, causing it to crash into farmland just short of Amsterdam’s Schiphol airport, killing nine people, including the three pilots, and injuring a further 50.The Dutch Safety Board has issued a warning to Boeing to prevent faulty radio altimeters influencing the autopilot.
However the role of the pilots has also been called into question. Pieter van Vollenhoven, chairman of the safety board, said the use of autopilot when landing was common practice at Turkish Airlines although policies varied between carriers.
“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.”
Black box flight data showed the altimeters 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 then triggered an automatic warning telling the pilots to deploy the plane’s undercarriage. The plane also lost speed. However the crew ignored both the warning and the loss of airspeed, according to Mr van Vollenhoven.
Only once the plane had slowed to stalling speed did the pilots react by applying full power, by which time it was to late for the plane to regain flight.
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.