Turkish Airlines 1951

Image taken from here

You all know about the crash of Turkish Airlines 1951, a Boeing 737-800 on approach to Amsterdam’s Schipol Airport. The investigators have released a possible cause of the crash.

It seems that a malfunctioning radio altimeter, the one on the captain’s side, was causing the autothrottle system to prematurely retard the throttles. At 1950 feet, the radio altimeter instantly displayed a reading of -8 feet. The autothrottle system thought that the airplane had landed, and proceeded to retard the throttles. This happened twice, first at the 1950 feet, where the captain took over the controls at 40 knots below minimum speed, and again when the captain released the throttles (possibly while struggling with the pitch change). The airplane hit the ground in a stalled condition.

The autopilot and the autothrottle systems both use input from the radio altimeters, but they are separate independent systems. The autopilot is switchable between the captain and first officer sides, and was selected to the good copilot radio altimeter when this happened. However, the autothrottle system is not switchable, and always uses the captain’s radio altimeter as its source.

There is a debate among pilot circles as to whether to blame the crash on the pilots or Boeing. My thoughts are that the dead pilots will probably ultimately be blamed, possibly with the Turkish Airlines training being modified. In any case, I would certainly recommend that when close to the ground, always keep one hand on the throttles, and have the other pilot back you up with her/her hand ready to take over at any time.

And, if the automatic stuff isn’t working, switch it off and fly the airplane yourself!

Be a pilot — not a passenger!