Investigation Summary
The flight from Beijing encountered unusually low ambient temperatures, reaching as low as -74°C over Siberia. This caused the fuel temperature to drop significantly, leading to the formation of soft ice crystals from the small amount of water typically suspended in jet fuel. During the final approach, as the autothrottle commanded an increase in thrust, the increased fuel flow caused these accumulated ice crystals to migrate and clog the face of the Fuel Oil Heat Exchangers (FOHE) on both Rolls-Royce Trent 800 engines. This restriction prevented the engines from producing the necessary thrust to reach the runway.
Final Conclusions
The AAIB concluded that the accident was caused by the accumulation of ice in the fuel system which restricted fuel flow to both engines. The specific design of the Trent 800 FOHE made it susceptible to blockage by ice crystals under specific cold-soak conditions. The crew's decision to adjust flaps helped reduce drag and extend the glide, which was instrumental in ensuring the aircraft cleared the perimeter fence and landed within the airfield boundary.
Video Analysis
British Airways Flight 38 Crash Landing at London Heathrow — This video analyzes the 2008 dual engine failure of a Boeing 777 caused by ice crystal restriction in the fuel system. It details the crew's emergency landing and the subsequent safety redesign of the heat exchangers.
Watch on YouTube ↗If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Fuel Oil Heat Exchanger (FOHE)
A component designed to cool engine oil using cold fuel; its narrow flow passages became the site of the ice blockage.
Autothrottle
The system was engaged during the approach and commanded the thrust increase that triggered the ice migration.
Trent 800 Engines
The Rolls-Royce engines suffered a 'rollback' where they failed to respond to throttle commands due to fuel starvation.
Interesting Facts
- 01The aircraft was the first Boeing 777 to be written off in the model's history.
- 02Fuel temperatures during the flight remained above the freezing point of the fuel itself, but low enough for water to freeze.
- 03The landing gear was sheared off during the impact and one part penetrated the cabin floor.
- 04The flight crew had only seconds to react to the loss of thrust at an altitude of approximately 720 feet.
- 05All 152 passengers and crew survived, with only one serious injury reported.