Altimeter fault behind Turkish Airlines crash in Amsterdam

A faulty altimeter caused the crash last week of a Turkish Airlines plane as it approached Amsterdam's Schiphol airport, killing nine people and injuring more than 80, investigators said yesterday.

The instrument relayed the wrong data to the automatic pilot, causing it to throttle back the engines as if the plane was just about to touch down, when it was really well short of the runway and still descending.

The pilots, who were among those killed in the February 25 crash, reacted too late to a stall warning and failed to pull the aircraft up in time, Dutch Safety Board president Peter van Vollenhoeven told journalists. Mr Van Vollenhoeven said bad weather, producing low cloud and fog, probably prevented the crew seeing the ground and realising they were too low. They apparently discounted the altimeter fault, which had occurred twice before in the same aircraft, he said.

"The voice recorder and the black box, both of which are in the hands of the Safety Board, show that an irregularity occurred during the descent, at 1,950 feet" (around 700 metres), he said.

"At a height of 1,950 feet the left radio altimeter suddenly showed a change in altitude - from 1,950 feet to minus eight feet - and passed this on to the automatic pilot.

"This change had a particular impact upon the automatic throttle system which provides more or less engine power" during the descent.

"The voice recorder has shown that the crew were notified that the left radio altimeter was not working correctly. Provisional data indicates that this signal was not regarded to be a problem," Mr van Vollenhoeven added.

"In practice, the plane responded to this sudden change as though it was at an altitude of just a few metres above the Polderbaan and engine power was reduced. "It seems that the automatic system assumed that it was in the final stages of the flight."