Understanding the Crash of Turkish Airlines Flight 1951
On February 25, 2009, Turkish Airlines Flight 1951 crashed just short of the runway while attempting to land at Amsterdam Schiphol Airport. Operating as a scheduled international passenger flight from Istanbul, the Boeing 737-800 carried 135 people on board, including 127 passengers and 8 crew members. Tragically, nine people lost their lives, and over eighty others sustained injuries. The disaster stunned the aviation community because the aircraft was modern, the weather conditions were calm, and the flight crew possessed extensive collective experience.
The official investigation into the accident revealed a complex chain of events centered on a faulty radio altimeter and a lack of crew awareness regarding automated flight systems. Rather than a single catastrophic failure, the tragedy highlighted vulnerabilities in automation dependency, crew resource management, and altimeter maintenance protocols.
The Sequence of Events on Approach
Flight 1951 departed Istanbul Atatürk Airport without incident. The journey across Europe was entirely routine. As the aircraft approached Amsterdam Schiphol Airport, air traffic control cleared the flight for an ILS (Instrument Landing System) approach to Runway 18R.
The first officer was flying the aircraft under the supervision of the captain. During the descent, the left radio altimeter—a device that measures the aircraft's exact height above the ground—malfunctioned. It suddenly indicated that the airplane was at minus eight feet (-8 ft), even though the jet was still hundreds of feet in the air.
This glitch triggered a severe cascading effect within the Boeing 737's automated flight systems. Because the left radio altimeter reported the plane was already on or near the ground, the auto-throttle system assumed the landing phase was complete. Consequently, the throttles automatically pulled back to idle to decrease engine power.
The Failure of Cockpit Awareness
As the auto-throttle reduced thrust to idle, the aircraft's speed began to bleed off. The flight crew failed to notice that the airspeed was dropping dangerously low.
Modern commercial airliners feature multiple safety alerts, including stick shakers that violently vibrate the control column to warn pilots of an impending aerodynamic stall. In this specific incident, the stall warning system activated briefly, but the crew did not recognize the warning signs or correlate the falling airspeed with the throttles resting at idle.
By the time the captain realized the aircraft was losing altitude and speed too rapidly, it was too late. The plane entered a full aerodynamic stall at a low altitude, leaving zero room for recovery. The aircraft slammed into a muddy field roughly one kilometer short of the runway threshold, breaking apart into three sections. Remarkably, the absence of post-crash fire prevented an even higher death toll.
Findings by the Dutch Safety Board
The Dutch Safety Board (Ovv) led the official investigation and published its comprehensive final report. Investigators pinpointed several critical factors that contributed to the accident:
- Radio Altimeter Failure: A known, intermittent fault in the left radio altimeter provided false height data to the flight management computers.
- Automation Design: The auto-throttle system's response to the erroneous altimeter reading lacked adequate safeguard redundancies.
- Crew Monitoring Deficiencies: The flight crew failed to monitor flight parameters, specifically airspeed and engine power output, during the final approach phase.
- Training Gaps: Airline training programs at the time did not adequately emphasize manual flight skills and monitoring automated systems during abnormal indications.
Following the crash, safety recommendations were issued globally. Boeing issued service bulletins regarding radio altimeter maintenance, and aviation authorities urged airlines to retrain pilots on monitoring airspeed indicators vigilantly during automated approaches.
Frequently Asked Questions
What caused Turkish Airlines Flight 1951 to crash?
The crash was caused by a faulty radio altimeter that tricked the auto-throttle system into reducing engine power to idle during final approach. The flight crew did not notice the decreasing airspeed until the aircraft entered an aerodynamic stall.
How many people survived the accident?
Out of the 135 people on board, 126 survived, though many sustained severe injuries. Nine occupants—four passengers and five crew members, including both pilots—tragically lost their lives.
Did Boeing make design changes after the accident?
Yes. The investigation prompted safety recommendations for Boeing 737 aircraft regarding altimeter systems and reinforced the importance of clear pilot alerts when flight parameters deviate unexpectedly.
What is a radio altimeter and why was it important?
A radio altimeter measures height above the terrain directly below the aircraft using radio waves. It differs from a standard barometric altimeter, which measures altitude based on atmospheric pressure. In modern jets, automated systems rely on radio altimeter data to execute automated landings and manage flare maneuvers.
