Table of Contents.

Scandinavian Airlines Flight 751, 1991. (Gottrörakraschen).


SAS "Dana Viking", reg.no. OY-KHO.

On December 27, in 1991, SAS flight 751 was ready for departure from Arlanda Airport, Stockholm. On board were 123 passengers and 6 in the crew. The Danish citizen, Stefan G. Rasmussen, was the airline Captain.



At 8:47 am, they took off from runway 08. After 25 seconds of flight, the right engine started surging (definition, see below). The Captain then retracted the engine throttle slightly, but the surging did not cease. After a further 1 minute the engine's traction force ceased. Shortly thereafter, the left engine began to surge and also it lost its traction force. They were now at altitude about 1000 m. The downhill began and the crew prepared for emergency landing. At altitude about 300 m they broke through the cloud cover. The Captain chose to land on a field that was largely in the flight direction. During the approach to the field they collided with trees. The plane cleared its way through the tree tops to the crash site. There it slides about 100 m through a clay field before it stopped. The total time of flight was about 4 minutes. All aboard survived. Eight were seriously injured, 84 minor injured and 37 not injured.
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Engine surging. (The Investigating Commission's report p. 23).
Aerodynamic disturbances in a compressor in operation can lead to engine surging. This occurs when the compressor at high power output is no longer capable of compressing the incoming air to the pressure present in the engine combustion chamber. The air current suddenly turns and pushes with heavy force in the opposite direction and a surge occurs. If the conditions are favorable, the engine usually recovers directly when the compressor and combustion chamber pressure drops. However, if the original aerodynamic disturbances persist, a new surge can be rapidly developed. Normally, repeated surging stops if the engine throttle is reduced sufficiently.
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The plane was broken in three parts at the crash. No fire occurred.


The plane cleared its way through the tree tops to the crash site.
Photo: The Investigation Commission.


The plane slides about 100 m through a clay field. Photo: SVT, News.






The red line shows the plane's approach towards the crash site. The nearest building was
Korsbro Torp. The property was inhabited. Coordinates for the site: 59 ° 46'06 "N 018 ° 07'55" E
Photo: Google.

The Investigating Commission has submitted a report, 1993-10-20. Some important conclusions:
"The Commission finds that the accident was caused by the fact that SAS's instructions and procedures were insufficient to ensure that clear-ice was removed from the aircraft's wings before starting. This prompted the airplane to start with clear-ice on the wings. In conjunction with the take off, clear-ice loosened and sucked into the engines. The ice caused damages to the engines' fans, which resulted in engine surging. The surging destroyed the engines.

Contributing reasons were:
1. The pilots were not trained to identify and repair engine surging
2. ATR - which was unknown to the SAS - was activated and increased the engine throttle without the pilots' knowledge. "
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My comment:
ATR, Automatic Thrust Restoration, is a system designed to reduce noise when the plane rises shortly after take off. The ATR automatically reduces the engine throttle to the optimal level. In case of failure on one engine, ATR automatically increases on the other. The Captain of the SAS flight 751 reduced the throttle when surging occurred on the right engine, but ATR automatically increased the throttle. When I compare this "accident" to the Linate Airport Disaster and the JAS 39 Gripen Crash,1993, I think that the CIA has taken control of the aircraft from the ground level. Clear-ice was not the problem.
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Here you can download the accident report: C1993_57_Gottrora.pdf         (9.4 MB, all in Swedish)

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