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Turkish Airlines Crash

Faulty altimeter caused airliner crash  Mar 04, 2009

The Turkish airliner that crashed at Schiphol last week had a faulty altimeter. That's the conclusion of the preliminary findings of the investigation team that has been working to establish the cause of the accident. The altimeter wrongly indicated that the Boeing was already almost on the ground. Because the airplane was flying on automatic pilot, the thrust was reduced according to the faulty reading. The pilots realised the problem, but had insufficient time to correct it.

The investigators have been examining the aircraft and the black boxes for the past week. Nine people lost their lives and approximately 80 were injured. 28 of the passengers remain in hospital. Pieter van Vollenhoven, head of the investigation board, told journalists that the preliminary findings reveal serious shortcomings in safety protocol, of which the board wants to warn the manufacturer, Boeing, and all airlines. For that reason, the preliminary findings have been published while further investigations continue:

"The voice recordings and black boxes in the possession of the Dutch Safety Board indicate that irregularities occurred during the plane's descent. At a height of 1,950 feet, around 700 metres, the left altimeter suddenly showed a change in altitude, which it transmitted to the automatic pilot, that had been engaged for the landing."

Pilot error

It transpires from listening to black box voice recorders that the altimeter had been giving false readings on two previous occasions, but apparently this was not fixed by Turkish Airlines. On this particular flight, one pilot was receiving training in making a landing by automatic pilot. The investigators say that too much time was spent exchanging information between the instructor and the trainee, and not enough was spent checking the actual readings which would have alerted the crew to the problem in time to override the automatic pilot. Low cloud may also have played a part in their failure to realise their actual height. The flying instructions for the aircraft should specifically have warned that the automatic pilot should not be used if the altimeter is not functioning correctly. And there is no failsafe system on this type of aircraft to prevent the automatic pilot from being used despite a faulty altimeter. This is regarded by the investigators as a serious shortcoming in the design of the aircraft.

Maintenance conflict

Another somewhat alarming fact has also come to light. Two weeks ago, a serious conflict arose between the union representing maintenance workers and the management of Turkish Airlines. The union warned the management of serious shortcomings in the maintenance system which could lead to safety risks in the air. The background to this conflict is that the number of maintenance staff has not kept pace with the rapid growth of the airline, which currently has about 130 aircraft. There is now talk of a reorganisation of the maintenance staff.

The investigators have therefore concluded that that blame for the accident must be shared between Turkish Airlines, the pilots and the manufacturer. The fact that human error was clearly involved means that it's likely that there will be legal repercussions, such as charges of negligence or even manslaughter.

Meanwhile, ongoing investigations will focus on the functioning of altimeters in relation to the automatic pilot. There will also be a closer investigation into the way Turkish Airlines trains its pilots.

Immediately after the publication of the results, Boeing alerted companies using the 737 to instruct their pilots to keep a close eye on their plane's instruments during crucial phases of the flight, such as take-off and landing.

Faulty altimeter caused airliner crash
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