Investigation Summary
The root cause of the fuel leak was a maintenance error involving the replacement of the right engine (No. 2) several days prior. Air Transat maintenance staff installed a hydraulic pump and associated lines from an older model engine. Because the clearances were different, the fuel line and hydraulic line were in direct contact. Over time, engine vibration caused the hydraulic line to chafe through the fuel line, creating a fracture. On the night of the accident, this fracture began leaking fuel at a rate of approximately one gallon per second. The pilots were initially alerted by low oil temperature and high oil pressure readings on the right engine, which were actually caused by the fuel leak cooling the oil as it sprayed out. Misinterpreting these unusual readings as a sensor anomaly, the crew failed to recognize the subsequent fuel imbalance as a leak. Following the standard operating procedure for an imbalance, they opened the cross-feed valve, effectively pumping their remaining fuel out of the hole in the right engine's fuel line.
Final Conclusions
The Portuguese Aviation Accidents Prevention and Investigation Department (GPIAA) concluded that the accident was caused by the rupture of a fuel pipe due to interference with a hydraulic line, a condition created by improper maintenance. Contributory factors included the crew's failure to follow the 'Fuel Leak' checklist when the imbalance was first detected and their decision to cross-feed fuel, which led to total fuel exhaustion. The successful landing was credited to the exceptional airmanship of the crew under extreme pressure, though the aircraft sustained structural damage and tire blowouts during the high-speed emergency touchdown.
Video Analysis
Air Transat Flight 236: The Atlantic Glide — An analysis of the 2001 fuel exhaustion incident where an Airbus A330 performed the longest unpowered glide in history following a maintenance error and fuel leak over the Atlantic Ocean.
Watch on YouTube ↗If playback is blocked, the owner has disabled embedding — use the link above.
Systems & Failure Modes
Fuel Cross-feed Valve
A valve that allows fuel to be transferred between the left and right wing tanks. Opening this valve during a leak allowed the remaining fuel to escape.
Ram Air Turbine (RAT)
A small wind turbine that deploys from the fuselage to provide emergency power when both engines fail.
Fuel/Oil Heat Exchanger (FOHE)
A component where fuel is used to cool engine oil. The leak occurred in a line downstream of this unit.
Interesting Facts
- 01The aircraft glided for approximately 19 minutes, covering 65 nautical miles (120 km).
- 02The landing speed was approximately 200 knots, significantly higher than the normal 140 knots.
- 03The Ram Air Turbine (RAT) provided the only source of electrical and hydraulic power after the dual engine failure.
- 04The fuel leak rate was estimated at 13 tonnes per hour.
- 05Captain Robert Piché had over 16,800 flight hours at the time of the accident.
Safety Actions & Advisories
FCOM Revision
Airbus revised the Flight Crew Operating Manual to emphasize that a fuel imbalance should be treated as a potential leak before cross-feeding.
Maintenance Training
Air Transat implemented stricter maintenance protocols regarding the use of parts from different engine versions and improved clearance inspections.