Safety Assumptions

Fuel Leak Detection

  • Standard operating procedure (SOP) fuel quantity checks will detect fuel loss before it becomes critical. At the time of the 30°W SOP check, the total fuel quantity onboard the airplane was within 1% of the planned fuel quantity at point in the flight.


  • The stabilizer trim tank transfer system automatic center of gravity control would not create an unsafe operating condition. It was not envisioned that a fuel leak would result in automatically transferring more fuel to the tank with the fuel leak to balance fuel and thus, delaying flight crew awareness of the fuel leak.

Configuration Control

  • The compatibility of components would be achieved by application of installation service bulletins. The configuration of the engines installed on the Air Transat A330 was a later configuration, and had previously incorporated hydraulic pump modifications. The loaned engine, however, had been supplied with an earlier version of the hydraulic pump installation that was not compatible with existing airplane hydraulic lines, leading to interference with adjacent fuel lines, and fuel line cracking, resulting in the fuel leak.

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