National Transportation Safety Board

摘要

Two recent events involving failure to achieve commanded thrust on Boeing 777-200 airplanes powered by Rolls-Royce RB211 Trent 800 series engines have caused the National Transportation Safety Board to be concerned about the potential for additional failures to occur. Testing following the two events has demonstrated that the Trent 800 series fuel/oil heat exchanger (FOHE) can be overwhelmed by ice formed inside the 777 fuel feed system from normal amounts of water present in jet fuel. This condition can restrict the fuel supply to both engines, resulting in failures to achieve commanded thrust. Procedures intended to mitigate this condition are in place, but the Safety Board is concerned that they are insufficient to prevent additional occurrences and that, until the present FOHE design is replaced by one more tolerant to ice accumulation, additional failure events may occur and could result in accidents and injuries. Although the investigations of these events are ongoing, the Board believes that immediate action is required to address this safety issue.