Scandinavian Airlines System Flight 751 was a regularly scheduled Scandinavian Airlines passenger flight from Stockholm, Sweden, to Warsaw, Poland, via Copenhagen, Denmark. On 27 December 1991, a McDonnell Douglas MD-81 operating the flight, registration OY-KHO, piloted by Danish Captain Stefan G. Rasmussen (44) and Swedish first officer Ulf Cedermark (34), both experienced pilots with 8,000 and 3,000 flight hours, respectively, was forced to make an emergency landing in a field near Gottröra, Sweden. Ice had collected on the wings' inner roots (close to the fuselage) before takeoff, broke off, and was ingested into the engines as the aircraft became airborne, ultimately disabling both engines. All 129 passengers and crew aboard survived.

The incident is known as the Gottröra crash () or the Miracle at Gottröra () in Sweden.

Aircraft

The aircraft involved was a McDonnell Douglas MD-81, MSN 53003, registered as OY-KHO, that was manufactured by McDonnell Douglas in 1991. It had logged approximately 1608 airframe hours and 1272 takeoff and landing cycles and was equipped with two Pratt & Whitney JT8D-217C engines.

Accident

The aircraft had arrived at Stockholm Arlanda Airport at 22:09 local time after a flight from Zürich the previous evening and was parked overnight at temperatures of around . About of very cold, flight-chilled fuel remained in the wing tanks. Due to this, clear ice had formed on the upper side of the wings, but was not detected. The aircraft was de-iced with of de-icing fluid, but not checked afterwards for remaining ice by the de-icing personnel or the Pilot-in-Charge, Captain Rasmussen, which he was required to do by the Scandinavian Airlines "Flight Deck Bulletin/Winterization" given to pilots.

The plane departed from Stockholm at 08:47. Shortly after liftoff, pieces of ice broke off and slammed into the fans of both engines, deforming the fan blades sufficiently to disturb the airflow to the compressors. The disturbed airflow caused the compressors to stall and this in turn caused the engines to surge. As the engines were not throttled down sufficiently, the surges continued. The high loads from repeated engine surges quickly led to the breakup of both engines.

From the pilots' point of view, after 25 seconds of flight, noises and vibrations caused by the no. 2 engine surging were first noticed. The flight crew responded by throttling down a little, but an automatic system, ATR (automatic thrust restoration), that had not been described to the flight crew by SAS, simultaneously increased throttle as a response to the asymmetric engine power and reduced climb rate. As a consequence, the engine surges continued. SAS Flight Captain Per Holmberg, who was on board as a passenger, noticed the problems early, hurried to the cockpit, and provided invaluable assistance to the crew. Engine no. 1 surged 39 seconds later and both engines failed at 76 and 78 seconds, respectively, into flight, at an altitude of .

The pilot responded to the loss of both engines by pitching the aircraft down in a dive before leveling it, to try to have it glide the longest possible distance without stalling. The pilots requested a return to Arlanda and attempted the restart procedure, but, with the aircraft emerging from cloud cover at altitude, they chose a field in the forest, near the Vängsjöberg seat farm in Gottröra, Uppland, for an immediate emergency landing.

During the final descent, the aircraft hit several trees, losing a large part of the right wing. It struck the ground tail-first, and the tail cone of the plane broke off. The plane slid across the field for , during which the main landing gear of the plane dug marks into the field and sheared off, the nose landing gear broke off, and the fuselage broke into three parts. As a result of the accident, 25 people were injured—two of them seriously—but there were no fatalities. The flight attendants had instructed passengers to adopt the brace position, which is credited with the lack of fatalities.

The flight crew, and especially Captain Rasmussen, were lauded for the skilled emergency landing in a fast-developing, potentially fatal situation. Rasmussen commented that "few civilian air pilots are ever put to a test of the skills they have acquired during training to this degree". He said he was proud of his crew and very relieved everyone had survived. He chose not to return to piloting commercial aircraft, after experiencing a lack of trust in the machinery he was piloting in simulator sessions following the accident. In 2022 he still suffered from PTSD from the aftermath of the accident when he was both called a hero and a villain despite him just believing he did the job he was trained for.

Investigation and recommendations

thumb|250x250px|Wreckage of the MD-81 from another view|alt=Wreckage of the MD-81 from another view

According to the official accident report by the Swedish Accident Investigation Board (SHK), the problem of clear ice formation on the wings in this type of aircraft was a well-known phenomenon at the time of the accident.

From 1985 onward, McDonnell Douglas gave extensive information, including several "All Operators Letters" that dealt with the clear ice problem. In the "All Operators Letter" of 14 October 1986, operators were informed of how the Finnish airline Finnair had solved the problem of discovering clear ice. In 1988 and 1989, McDonnell Douglas arranged "Theme Conferences" dealing with clear ice formation. SAS took part in these conferences.

See also

  • List of airline flights that required gliding
  • Ural Airlines Flight 178 – 2019 accident after both engines failed following a bird strike shortly after takeoff
  • US Airways Flight 1549 – 2009 accident after both engines failed following a bird strike shortly after takeoff
  • British Airways Flight 38, a case where ice in the fuel system blocked the engines from receiving the fuel they needed, leading to dual engine failure
  • Southern Airways Flight 242, a flight that experienced dual engine failure after their engines ingested hail
  • TACA Flight 110, a flight that suffered dual engine failure after their engines ingested an extreme amount of rain
  • Lion Air Flight 610 and Ethiopian Airlines Flight 302, flights where a safety system unknown to the flight crew caused an accident

References

  • Swedish Accident Investigation Board (SHK)
  • Final report <!--Old URL: http://www.havkom.se/virtupload/content/101/C1993_57e.pdf--> – Translated from the original Swedish by Tim Crosfield M.A., at the request of the SHK. (Archive)
  • Final report <!--Old URL: http://www.havkom.se/assets/reports/C1993_57_Gottrora.pdf--> – The original version. (Archive)
  • Radio documentary from Swedish Radio P3 about the incident. (Swedish)
  • Scandinavian Airlines System (SAS) Flight 751 Accident Animation