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 on 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 if 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.
The deputy chairman of the Turkish pilots’ association, Ahmet Izgi, told Turkey’s NTV news channel that the preliminary Dutch findings were “not satisfactory” and said it would be odd for the pilots to not react to a false altimeter reading in time to save the plane.
The Turkish Civil Aviation Directorate said the “announcements and given answers are far from clarifying the reasons behind the accident and bringing about a conclusion.”
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.
At 1950 feet the airplane’s left altimeter suddenly and mistakenly registered an altitude of 8 feet below sea level and passed the reading on to the automatic control system, Van Vollenhoven said.
According to conversation recorded between the plane’s captain, first officer and an extra first officer on the flight, the pilots noticed the faulty altimeter but didn’t consider it a problem and didn’t react, Van Vollenhoven said.
But the autopilot reduced gas to the engines and the plane lost speed, decelerating until, at a height of 450 feet it was about to stall. Warning systems alerted the pilots.
“It appears that then the pilots immediately gave gas, full gas, however it was too late to recover,” Van Vollenhoven said. He said it would be for courts to apportion blame.
The plane fell into a freshly plowed field, striking the ground tail first and breaking into three pieces.
Eyewitnesses said it seemed to fall from the sky. Passengers who survived had noticed the pilot gunning the engines at the last minute.
Those killed in the crash included five Turks and four Americans.
Turkish Airlines said the dead included the three pilots. It described the captain, Hasan Tahsin Arisan, as an experienced pilot and air force veteran.
The American dead included three Boeing employees on a business trip unrelated to the flight.
As of Wednesday, 28 survivors are still hospitalized.
Talk to us
> Give us your news tips.
> Send us a letter to the editor.
> More Herald contact information.
