Lessons Learned

Technical Related Lessons

A large, undetected fuel leak poses a substantial risk to safety of flight, especially on long range flight routes. (Threat Category:  Fuel Exhaustion)

  • As the flight progressed, and between fuel quantity checks at planned flight waypoints, a massive fuel leak developed on the right engine. Investigators concluded that an automated system which continuously monitors available fuel would have allowed the crew to determine that fuel was being consumed at a higher than planned rate, and may have allowed an earlier decision to divert to an alternate airport, and avoid fuel exhaustion.

Common Theme Related Lessons

There are some effects of highly automated systems that can mask other system failures, originating from independent sources, that may pose an ongoing threat to flight safety. (Common Theme:  Unintended Effects)

  • Forward fuel transfer from the stabilizer trim tank, that balanced fuel in the main fuel tank feeding the leaking right engine masked the fuel leak for about 25 minutes and contributed to an unnoticed loss of 3,500 kg (7,718 lbs.) of fuel. The investigators noted that a clear, unambiguous alert of a critical low fuel condition would have provided crew awareness sufficiently early to allow corrective action and avoid fuel exhaustion. Flight crew confusion over flight deck indications, with an initial assumption that lower than expected fuel quantities were a result of a fuel quantity indicating error, and automatic fuel transfer of fuel from the stabilizer trim tank resulted in delayed awareness of a critical fuel loss.

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