Washington, DC - National Transportation Safety Board Acting Chairman Mark V. Rosenker today praised the work of all the investigators looking into the crash of a Boeing 777 at London's Heathrow Airport in January, saying that the recommendations issued today "show how international cooperation can lead to safety improvements that benefit the aviation community worldwide."
The United Kingdom's Air Accidents Investigation Branch (AAIB), which is leading the investigation into the January 17, 2008, accident in which a British Airways Boeing 777- 236ER landed short of Runway 27L at London Heathrow Airport, issued an interim report today on the progress of the investigation.
The interim report contains recommendations aimed at addressing a circumstance identified by investigators relating to Rolls Royce-powered Boeing 777 aircraft. The investigation has shown that both engines lost power in the final minute of flight because the fuel flow to each engine was restricted; most probably due to an accumulation of ice within the engine fuel feed system. The ice is likely to have formed from water - which exists naturally in the fuel - while the aircraft operated for a long period, with low fuel flows, in the cold environment associated with high-altitude flight.
In accordance with established international arrangements, the National Transportation Safety Board, representing the State of Design and Manufacture of the aircraft, appointed an Accredited Representative to participate in the investigation. The Accredited Representative is being supported by a U.S. team that includes NTSB specialists, the Federal Aviation Administration, and Boeing. Rolls-Royce, the engine manufacturer, is also participating in the investigation. British Airways, the operator, is cooperating with the investigation and providing expertise as requested by the AAIB.
This interim report updates and provides further details on the history of the flight and the research done by teams in both the U.K. and U.S. using data obtained from the accident aircraft, and similar aircraft in the British Airways fleet.
The report further details the aircraft fuel systems and describes testing performed in laboratories, on an adapted fuel rig using actual aircraft components, in an engine test facility, and on an exemplar engine. In conclusion, the report provides recommendations for both interim action and longer term changes to certification criteria.
Acting Chairman Rosenker stated, "When it comes to aviation safety, there are shared interests that transcend national borders." Rosenker noted that the U.S. Accredited Representative and technical advisors fully participated in the development of the factual material and supporting research and that the recommendations are supported by the U.S. team.
The investigation team indicated that a change to the fuel system design would make the system more resilient, but would take time to implement. Therefore, to reduce the risk of recurrence interim measures need to be adopted until such design changes to the fuel system are available.
Therefore, the AAIB recommends that:
The Federal Aviation Administration and the European Aviation Safety Agency, in conjunction with Boeing and Rolls Royce, introduce interim measures for the Boeing 777, powered by Rolls Royce Trent 800 engines, to reduce the risk of ice formed from water in aviation turbine fuel causing a restriction in the fuel feed system (AAIB 2008-047), that
In two cases a build-up of ice on the fuel/oil heat exchanger restricted the flow, resulting in an uncommanded engine rollback.
The new AD adds further procedures to prevent ice buildup that can clog fuel lines.
Aircraft experienced an uncommanded engine rollback in the cruise phase of an intercontinental flight.
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