THE HAGUE (Reuters) - A faulty altimeter shut down the engine of the Turkish Airlines flight before it crashed last week near Amsterdam airport killing nine people, Dutch authorities said.
They said similar shutdowns had occurred twice before on the same plane and were overruled by the pilots, and warned its maker Boeing and any airlines using 737 models to be vigilant.
When flying at about 1,950 feet the plane’s left radio altimeter indicated the Boeing 737-800 was flying at minus 8 feet, prompting the automatic pilot to shut down the engines, the Dutch Safety Board said on Wednesday.
“The crew initially did not react to these events,” Dutch Safety Board head Pieter van Vollenhoven told reporters.
When an alarm went off that the plane’s speed would drop below the minimum, the pilots reacted and reignited the engines.
“But the plane was too low at 150 meters. As a consequence the plane crashed 1 kilometer before the runway,” said Van Vollenhoven.
“The reason to go public now already is to warn Boeing and all users of this plane type that vigilance is required with regards to the altimeter,” he said.
Boeing said in an statement it was “issuing a reminder to all 737 operators to carefully monitor primary flight instruments during critical phases of flight.”
The plane’s black box — which can register 25 hours of flying time and in this case had covered 8 flights— showed the problem had occurred twice previously during landings.
In the first instances the pilot had overruled the automatic pilot and restarted the engines, a spokesman for the Safety Board said. Investigations were underway as to why more action had not been taken after the problem was detected.
Five Turks and four Americans were killed when the plane plunged into a boggy field while trying to land last week at Amsterdam’s Schiphol, Europe’s fifth-largest airport by passenger numbers and third largest by freight volume.
Passengers said the plane suddenly dropped to the ground during landing.
Braking caused when the plane hit the ground meant that the aircraft broke into two pieces and the tail broke off.
Most of the fatally wounded were near the rupture, in business class, and the three crew members in the cockpit died as a result of the enormous braking forces.
The section that remained most intact was situated around the plane’s wings.
Among the dead were three pilots and a flight attendant. The plane carried 127 passengers and 7 crew, of whom 28 are still in hospital.
“We are focusing the investigation on the malfunctioning radio altimeter and its consequences. Whether there could have been a different reaction will take more time to find out,” Van Vollenhoven said.
A trainee pilot was flying the plane before the crash took place, Van Vollenhoven said, and he declined to say whether this had any impact on the events.
Misty weather and low clouds meant the runway was not yet visible at the height at which the descent started.
“The plane was in heavy fog. I think the pilots did not see that a problem was occurring,” Van Vollenhoven said.
The Safety Board had not detected any other malfunctions of the plane, and did not have indications that the airport’s instructions or air turbulence played a role in the crash, Van Vollenhoven said.
The aircraft initially hit the ground in a field with its tail followed by its undercarriage, with a forward speed of 175 km per hour on impact. An aircraft should normally have a speed of 260 km per hour for landing, the safety board said.
Additional reporting by Gilbert Kreijger in Amsterdam, and Bill Rigby in Seattle; editing by Philippa Fletcher