What happened
Turkish Airlines Flight 1951, a Boeing 737-800, was performing a descent toward Amsterdam-Schiphol International Airport after departing from Istanbul. During the approach, the aircraft was vectored to intercept the glidepath for runway 18R at an altitude of approximately 2000 feet. While descending, the left-hand radio altimeter experienced a sudden error, displaying an incorrect altitude of -8 feet. Because the aircraft's systems relied on this faulty data, the autothrottle incorrectly entered the 'retard flare' mode, which is typically reserved for the final moments of landing below 27 feet. This caused the engine thrust to drop to approach idle.
While the autothrottle reduced power, the autopilot continued to attempt to maintain the glidepath based on the correct altitude readings from the right-hand system. This led to a significant increase in the aircraft's angle of attack to compensate for the loss of airspeed. The crew did not immediately recognize the deteriorating flight conditions despite visual indicators on the primary flight displays, including a flashing airspeed indicator and a high nose attitude.
At 460 feet, the approach to stall warning (stick shaker) activated. The pilot flying attempted to recover by pushing the control column and throttles forward; however, the captain took control during this process, which interrupted the thrust application. The autothrottle subsequently pulled the levers back to idle once disconnected. By the time full thrust was applied, the aircraft had already entered a stall. At an altitude of roughly 350 feet, the Boeing 737-800 impacted farmland, resulting in the destruction of the airframe and the separation of the engines and landing gear.
Findings
- The primary cause was a faulty radio altimeter reading on the left-hand system that triggered an inappropriate autothrottle mode.
- The flight crew did not identify the airspeed decay and high pitch attitude until the stick shaker activated.
- Conflicting control inputs between the crew members during the stall recovery prevented the timely application of necessary thrust.