The invisible ice that disabled both engines of a McDonnell Douglas MD-81
In short: On a cold December morning in 1991, SAS Flight 751 took off from Stockholm with a hidden danger. Clear ice, undetected on the wings, was about to enter the engines, triggering a catastrophic failure that nearly ended in tragedy.
The incident, known in Sweden as the Gottrørakraschen, began when an MD-81 arrived at Stockholm/Arlanda airport at 10:09 pm on December 26, 1991. The aircraft had been parked outdoors overnight in temperatures around 0 to 1 °C. Because the wing tanks contained approximately 2,550 kg of flight-chilled fuel, clear ice formed on the upper surfaces of the wings. While ground crews noted frost and slush during morning inspections, the specific presence of clear ice went undetected.
During the 8:30 am de-icing process, the crew focused on removing slush and frost from the underside of the wings. Although the aircraft was equipped with nylon tufts on the upper wing surface to help identify ice, the presence of clear ice was not confirmed. As the aircraft climbed after its 8:47 am departure, pieces of ice broke free and were ingested into both Pratt & Whitney JT8D-217C engines. This debris damaged the fan stages, causing the compressors to stall and the engines to surge.
A critical complication involved the Automatic Thrust Restoration (ATR) system. When the number 2 engine began surging 25 seconds into flight, the crew attempted to throttle down. However, the ATR system—designed to maintain climb performance by automatically advancing throttles during an engine failure—simultly increased thrust. This prevented the crew from stopping the surges, leading to the destruction of both engines by 78 seconds into the flight. Despite the fuselage breaking into three pieces upon impact in a field near Gottröra, all 129 people on board survived.
Opens the Intellect+ feed with this card first. Swipe up for the next one.
Sources
- Summary by Intellect · source: McDonnell Douglas MD-81 | Federal Aviation Administration
- Also: Scandinavian Airlines System Flight 751
To cite this card, link to https://intellectplus.co.uk/app/places-scandinavian-airlines-system-flight-751.
How we source, check and correct cards: Editorial standards.
General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.
Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?
Related
More in Countries and other regions · More in Countries & Cities · Latest · A–Z · All topics
