The software that betrayed Flight 751
Summary
This episode investigates Scandinavian Airlines Flight 751, where a McDonnell Douglas DC-9 lost both engines shortly after takeoff due to invisible ice ingestion. The crew executed a miraculous glide landing in a forest, saving all 129 souls aboard. Investigators discovered a hidden software feature, the Automatic Thrust Restoration System, had overridden the captain’s attempts to reduce power, causing catastrophic engine failure. The story highlights the dangers of undocumented automation and the profound psychological impact on the pilots.
Topics discussed
Introduction: The nightmare scenario of SAS Flight 751
Pre-flight conditions: Sauna cabin and de-icing procedures
The hidden danger: Cold-soaked fuel and invisible clear ice
Takeoff: Ice shatters and is ingested by rear engines
Engine failure: Compressor surge and titanium blade damage
The ghost in the machine: Automatic Thrust Restoration System
Total power loss and the APU restart by a passenger pilot
The glide: Ignoring ATC to preserve energy for landing
Impact and survival: Crashing into the pine forest
Investigation: Forensic evidence and mysterious throttle movements
The culprit: Undocumented software override by manufacturer
Aftermath: Procedural changes and the pilot's psychological toll
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