AMSTERDAM — A false reading from a faulty altimeter caused an autopilot to sharply slow a Turkish Airlines jet short of the runway last month, sending it plunging into a muddy field and killing nine people, Dutch investigators said Wednesday.
The flight carrying 135 passengers and crew crashed less than a mile from Amsterdam’s Schiphol Airport as it was landing Feb. 25. The pilots were among the dead.
One of the plane’s altimeters, a device that measures altitude, had registered that the plane was flying below sea level and caused the autopilot to rapidly reduce power before the crash, officials said.
The Boeing 737-800’s flight recorders showed false readings from the same altimeter on two flights before the crash, chief investigator Pieter van Vollenhoven said. He did not say whether pilots had noticed the previous incorrect readings.
The Dutch Safety Authority said it had issued a warning to Boeing as a result of its investigation, asking the company to alert customers that when altimeters are not functioning properly, “the automatic pilot and the gas system coupled to them may not be used for approach and landing,” van Vollenhoven said.
Boeing said it was reminding all operators of its 737s to carefully monitor primary flight instruments during critical phases, adding that it was carefully monitoring the fleet.
Van Vollenhoven said landing the plane on autopilot was not unusual and the pilots could not see the runway as the plane began its descent because of clouds and a light rain.
Those killed in the crash included five Turks and four Americans. The American dead included three Boeing employees. As of Wednesday, 28 survivors were still hospitalized.
