Turkish Airlines Flight 1951 crash

The aircraft, a Turkish Airlines Boeing 737-800, crashed into a field approximately 1.5 kilometres (0.93 mi) north of the Polderbaan runway, (18R), prior to crossing the A9 motorway inbound, at 9:31 UTC (10:31 CET), having flown from Istanbul, Turkey. The aircraft broke into three pieces on impact. The wreckage did not catch fire.

A preliminary investigation found that 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.

Background

Aircraft

The aircraft, built in 2002, was a Next Generation Boeing 737-800 series model 8F2 with registration TC-JGE, named "Tekirdağ". The model −8F2 denotes the configuration of the 737-800 built for use by Turkish Airlines. They have 51 aircraft of this model in service.

Flight

There were 128 passengers and seven crew members on board. The plane was under the command of Instructor Captain Hasan Tahsin Arisan, one of the airline's most experienced senior pilots. A former Turkish Air Force fleet commander, Captain Arisan had been working for Turkish Airlines since 1996. He had over 5,000 hours of flight time on the F-4E Phantom II. The other flight deck crew members were Olcay Özgür, safety pilot, sitting in the cockpit's center jump seat, and Murat Sezer, co-pilot under line training, flying as co-pilot. The cabin crew consisted of Figen Eren, Perihan Özden, Ulvi Murat Eskin, and Yasemin Vural.

Landing and damage

The plane 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 100 metres (300 ft) from the fuselage.

Aftermath

While several survivors and witnesses indicated that it took rescuers 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 three cockpit crew members were the last to be removed from the plane, at around 20:00 that evening, because the cockpit had to be examined before it could be cut open to get to these crew members. Also, some of the survivors say that at least 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 after.

All flights in and out of Schiphol Airport were suspended, according to an airport spokeswoman. Several planes were diverted to Rotterdam The Hague Airport as well as to Brussels Airport. At about 11:15 UTC, it was reported that the Kaagbaan runway (06/24) had been re-opened to air traffic, followed by the Buitenveldertbaan runway (09/27).

Turkish Airlines continues to use Flight 1951 on its Istanbul (Atatürk) to Amsterdam route.

Investigation

The investigation was led by the Dutch Safety Board (DSB, Dutch: Onderzoeksraad voor Veiligheid or OVV), and assisted by an expert team from Turkish Airlines and a representative team of the American NTSB, accompanied by advisors from Boeing and the FAA, Turkish Directorate General of Civil Aviation (SHGM), the operator, the UK Air Accidents Investigation Branch, and the French Bureau d'Enquêtes et d'Analyses pour la sécurité de l'Aviation Civile (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 initially asked the DSB to hand over the black boxes, but the DSB refused to do so. It stated that there was no indication of homicide, manslaughter, hijacking or terrorism, which would warrant an investigation by the prosecution.

A preliminary investigation of the data by the Dutch Safety Board released on 4 March 2009 reported that, while on final approach for landing, the aircraft was "fast and high on the glideslope", at about 2,000 ft (610 m) above ground, when the left-hand (captain's) radio altimeter suddenly changed from 1,950 feet (590 m) to read −8 feet (−2.4 m) 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 ("TOO LOW!, GEAR!") that indicated that the aircraft's landing gear should be down, as the aircraft was, according to the radio altimeter, flying too low. Later, the safety board's preliminary report modified this analysis, indicating 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, but the autothrottle unexpectedly reverted to "retard" mode, which is designed to automatically decrease thrust shortly before touching down on the runway at 27 feet (8.2 m) above runway height. At 144 kt, 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 83 knots (154 km/h), some 40 knots (74 km/h) below reference speed as the aircraft descended below the required height to stay on the glideslope. The stick-shaker activated at about 150 metres (490 ft) above the ground, indicating an imminent stall, the autothrottle advanced, and the captain attempted to apply full power. The engines responded, but there was not enough altitude or forward airspeed to recover; the aircraft hit the ground tail-first at 95 knots (176 km/h).

It is unknown if the pilots were aware of the decreasing speed, and if they were aware that the wrong altitude measurement directed autothrottle action. The autothrottle (and thus its retard mode) could have been switched off by pressing either the A/T disengage buttons or switching off the autothrottle "ARM" switch.

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 accident but rescuers were unable to reach him via the cockpit door due 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.

On 6 May 2010 the final report was released. Turkish Airlines disputes crash inquiry findings on stall recovery.

Passengers

The Schiphol authorities confirmed nine fatalities and a total of 86 injuries during a press conference. Five of the deceased victims were Turkish citizens, including the pilot, the co-pilot, a trainee 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 (AEW&C) program for the Turkish military.

Initial reports had six passengers in critical condition, 25 had sustained severe injuries, 24 minor injuries and 31 injuries of which the seriousness had still to be confirmed. By 9 March, there were still 23 in hospital, one of whom was in critical condition.

Within hours of the crash, Turkish Airlines published the passenger list. The Dutch authorities stated the following day that the plane carried 53 passengers from the Netherlands, 51 from Turkey, seven from the United States, three from the United Kingdom, one each from Germany, Bulgaria, and Italy, and one from either Thailand or Taiwan.

Among the passengers were the sisters Jihad and Hajar Alariachi, presenters of the Dutch television programme De Meiden van Halal. Jihad and Hajar were taken to hospital with minor injuries.

Dramatization

The story of the disaster was featured on the tenth season of Canadian TV series Mayday, the episode is entitled "Who's in Control?".

The flight was documented on an episode of the television program Why Planes Crash titled "Who's Flying".