2009 aviation accident
Turkish Airlines Flight 1951 (also known as the Poldercrash or the Schiphol Polderbaan incident) was a passenger flight that crashed during landing at Amsterdam Schiphol Airport, the Netherlands, on 25 February 2009, resulting in the deaths of nine passengers and crew, including all three pilots.
The aircraft, a Turkish Airlines Boeing 737-800, crashed into a field about north of the Polderbaan runway (18R), prior to crossing the A9 motorway inbound, at 09:26 UTC (10:26 CET), having flown from Istanbul, Turkey. The aircraft broke into three pieces on impact. The wreckage did not catch fire.
The crash was caused primarily by the aircraft's automated reaction, which was triggered by a faulty radio altimeter. This caused the autothrottle to decrease the engine power to idle during approach. The crew noticed this too late to take appropriate action to increase the thrust and recover the aircraft before it stalled and crashed. Boeing has since issued a bulletin to remind pilots of all 737 series and BBJ aircraft of the importance of monitoring airspeed and altitude, advising against the use of autopilot or autothrottle while landing in cases of radio altimeter discrepancies.
A 2020 investigation by "The New York Times" found that the Dutch investigation into the crash "either excluded or played down criticisms" of Boeing following pressure from Boeing and US federal safety officials, who instead "emphasized pilot error as a factor ... rather than design flaws."
Background.
Aircraft.
The aircraft operating Flight 1951 was a 7-year-old "Next Generation" Boeing 737-800 series model 8F2 with registration "TC-JGE", named "Tekirdağ". "Model 8F2" denotes the configuration of the 737-800 built for use by Turkish Airlines. It had 51 aircraft of this model in service at the time of the crash. The aircraft made its first flight on 24 January 2002 and was delivered to Turkish Airlines on March 27.
Flight.
On board were 128 passengers and seven crew members. The flight was under the command of Instructor Captain Hasan Tahsin Arisen (age 54). A former Turkish Air Force fleet commander, Captain Arisen had been working for Turkish Airlines since 1996 and was one of the most experienced pilots at the airline. He had over 5,000 hours of flight time on the F-4E Phantom II. Olgay Özgür (age 28) was the safety pilot of the flight, a graduate of a flight school in Ankara, who flew the MD-80 for World Focus Airlines before joining Turkish Airlines and passing the 737 type rating in 2006; he was sitting in the cockpit's center jump seat. Murat Sezer (42), co-pilot under line training, was flying as co-pilot. The cabin crew consisted of Figen Eren, Perihan Özden, Ulvi Murat Eskin, and Yasemin Vural.
Accident.
The flight was cleared for an approach on runway 18R (also known as the Polderbaan runway), but came down short of the runway threshold, sliding through the wet clay of a plowed field.
The aircraft suffered significant damage. Although the fuselage broke into three pieces, it did not catch fire. Both engines separated and came to rest from the fuselage.
While several survivors and witnesses indicated that rescuers took 20 to 30 minutes to arrive at the site after the crash, others have stated that the rescuers arrived quickly at the scene. About 60 ambulances arrived along with at least three LifeLiner helicopters (air ambulances, Eurocopter EC135), and a fleet of fire engines. An unconfirmed report by "De Telegraaf" states that the firefighters were at first given the wrong location for the crash site, delaying their arrival. Lanes of the A4 and A9 motorways were closed to all traffic to allow emergency services to quickly reach the site of the crash.
The bodies of the three cockpit crew members were the last to be removed from the plane, around 20:00 that evening, because the cockpit had to be examined before it could be cut open to get to these crew members. Some of the survivors said that one of the pilots was alive after the crash. The relatives of the passengers on the flight were sent to Amsterdam by Turkish Airlines shortly afterward.
All flights in and out of Schiphol Airport were suspended, according to an airport spokeswoman. Several planes were diverted to Rotterdam The Hague Airport and to Brussels Airport. Around 11:15 UTC (12:15 CET), the Kaagbaan runway (06/24) was reported to have been reopened to air traffic, followed by the Buitenveldertbaan runway (09/27).
Turkish Airlines continues to use the flight number 1951 on its Istanbul-to-Amsterdam route, primarily operated by an Airbus A321neo and an Airbus A330.
TC-JMJ, an Airbus A321 delivered two days after the accident to Turkish Airlines was named Tekirdağ in memory of the flight.
Investigation.
The investigation was led by the Dutch Safety Board (DSB, or "OVV"), and assisted by an expert team from Turkish Airlines and a representative team of the American National Transportation Safety Board (NTSB), accompanied by advisors from Boeing and the Federal Aviation Administration (FAA), Turkish Directorate General of Civil Aviation (SHGM), the operator, the UK Air Accidents Investigation Branch, and the French "Bureau of Enquiry and Analysis for Civil Aviation Safety" (BEA). The cockpit voice recorder and the flight data recorder were recovered quickly after the crash, after which they were transported to Paris to read out the data. The Dutch public prosecution service initially asked the DSB to hand over the black boxes, but the DSB refused to do so. It stated that no indication of homicide, manslaughter, hijacking, or terrorism was present, which would warrant an investigation by the prosecution.
While on final approach for landing, the aircraft was about 2,000 ft (610 m) above ground, when the left-hand (captain's) radio altimeter suddenly changed from to read altitude, although the right-hand (co-pilot's) radio altimeter functioned correctly. The voice recording showed that the crew was given an audible warning signal (landing gear warning horn) that indicated that the aircraft's landing gear should be down, as the aircraft was, according to the captain's radio altimeter, flying too low. This happened several times during the approach to Schiphol. The reason that the captain's radio altimeter was causing further problems was the first officer making a mistake when arming the aircraft's autopilot system for a dual channel ILS (Instrument Landing System) approach.
The Boeing 737NG has two autopilot systems or flight control units (FCU), which can work independently of each other (single channel) or together (dual channel). These systems are called CMD A and CMD B. CMD A is the left-seat FCU (Captain), while CMD B is the right-seat FCU (First Officer). During normal operations, the PF (Pilot Flying) uses their respective FCU. This is referred to as a "single channel". However, if the crew intended to fly an auto-land, which is when the airplane flies the approach and landing itself (During a CAT III ILS Approach), one would engage both FCUs, this way the approach can be flown to greater precision in bad visibility, allowing the pilots to lower the MDA (Minimum decision altitude) to 50 ft. This is called a "dual channel". Turkish Airlines' standard operating procedure at the time stated that all approaches should be flown "dual channel" when available, but the inexperienced (on the 737NG) first officer forgot to arm approach mode in the aircraft's mode control panel (MCP) before he engaged CMD A to make the approach "dual channel", meaning that the aircraft thought the pilots wanted to do a single-channel approach using CMD A (captain's autopilot) only. However unbeknownst to the pilots CMD A had a radio altimeter fail, which would be the main contributor to the accident. Later, the safety board's preliminary report indicated that the flight data recorder history of the captain's radio altimeter showed 8191 feet (the maximum possible recorded) until the aircraft descended through 1950, then suddenly showed negative 8 feet.
The throttles were pulled back to idle thrust to slow the aircraft to descend and acquire the glideslope. However, the autothrottle unexpectedly switched to "retard mode", a setting designed to reduce thrust to idle at above the runway, just before touchdown. In this mode, the autothrottle "holds" the thrust at idle, overriding any subsequent manual adjustments by the pilots. At , the pilots manually increased thrust to sustain that speed, but the autothrottle immediately returned the thrust lever to idle power because the first officer did not hold the throttle lever in position. The throttles remained at idle for about 100 seconds while the aircraft slowed to , below the reference speed as the aircraft descended below the required altitude to stay on the glideslope. The stick-shaker activated about above the ground, indicating an imminent stall, the autothrottle advanced, and the captain attempted to apply full power. The engines responded, but not enough altitude or forward airspeed was available to recover, and the aircraft hit the ground tail first at .
The data from the flight recorder also showed that the same altimeter problem had happened twice during the previous eight landings, but that on both occasions, the crew had taken the correct action by disengaging the autothrottle and manually increasing the thrust. Investigations are underway to determine why more action had not been taken after the altimeter problem was detected. In response to the preliminary conclusions, Boeing issued a bulletin, Multi-Operator Message (MOM) 09-0063-01B, to remind pilots of all 737 series and Boeing Business Jet (BBJ) aircraft of the importance of monitoring airspeed and altitude (the "primary flight instruments"), advising against the use of autopilot or autothrottle while landing in cases of radio altimeter discrepancies. Following the release of the preliminary report, Dutch and international press concluded that pilot inattention caused the accident, though several Turkish news publications still emphasized other possible causes.
On 9 March 2009, the recovery of the wreckage started. All parts of the plane were moved to an East Schiphol hangar for reconstruction.
It was reported that the first officer survived the crash itself, but that rescuers were unable to reach him via the cockpit door, owing to security measures introduced in the wake of the September 11, 2001 attacks. The rescuers eventually cut their way into the cockpit through the roof, by which time the first officer had died.
The final report was released on 6 May 2010. The DSB stated that the approach was not stabilized; hence, the crew ought to have initiated a go-around. The autopilot followed the glide slope, while the autothrottle reduced thrust to idle, owing to a faulty radio altimeter showing an incorrect altitude. This caused the airspeed to drop and the pitch attitude to increase; all this went unnoticed by the crew until the stick-shaker activated. Prior to this, air traffic control caused the crew to intercept the glide slope from above; this obscured the erroneous autothrottle mode and increased the crew's workload. The subsequent approach to stall recovery procedure was not executed properly, causing the aircraft to stall and crash. Turkish Airlines disputed the crash inquiry findings on stall recovery.
Passengers.
Nine fatalities and a total of 120 injuries occurred, with 11 of them serious. Five of the deceased were Turkish citizens, including the captain, the first officer, a line -training pilot, and one member of the cabin crew. Four were Americans, of whom three have been identified as Boeing employees stationed in Ankara and working on an Airborne Early Warning and Control program for the Turkish military. ;ref name="TC/Tubantia" ; ;/ref ;
The plane carried 53 passengers from the Netherlands, 51 from Turkey, 7 from the United States, 3 from the United Kingdom, 1 each from Germany, Bulgaria, Italy, and Taiwan.
Confidential information onboard.
Following media speculation, a spokesperson for the prosecutor's office in Haarlem confirmed in April 2009 to Agence France-Presse that instructions were given following the crash to remove four Boeing laptops from the wreckage, and that the laptops were handed over to the US embassy in The Hague. According to Dutch newspaper "De Telegraaf", the Boeing employees on board were in possession of confidential military information.
Turkish media outlets "Radikal" and "Sözcü" also reported that the Boeing employees on board were in possession of confidential military information, and that the rescue response was delayed because American officials had specifically requested from Dutch authorities that no one was to approach the wreckage until after the confidential information was retrieved.
According to "Radikal", the then-CEO of Turkish Airlines, Temel Kotil, had also stated that a Turkish Airlines employee stationed at Schiphol Airport had arrived at the crash site with his apron-access airport identification, but was prevented from reaching the wreckage, and was handcuffed