Europe, U.S. Regulators To Issue Rolls-powered Boeing 777 Airworthiness Directive

 - September 8, 2008, 9:36 AM

European and U.S. regulators have agreed to mandate “aircraft level” action for Rolls-Royce Trent 800-powered Boeing 777s and are considering potential action for other certified aircraft/engine combinations. This follows recommendations in an interim UK Air Accidents Investigation Branch (AAIB) report published Thursday into the British Airways 777 accident at London Heathrow Airport in January.

The 777 lost power during final approach and made a forced landing about 1,000 feet short of the runway after ice that formed in the fuel system restricted fuel flow to the engines. Although the exact mechanism remains unknown, the AAIB said, “ice could cause a restriction in the fuel feed system” and that the risk of recurrence should be addressed in the short term while investigation continues. “Further testing will be carried out to establish more clearly how ice forms within the fuel system and how it might cause the restricted fuel flows seen on this flight,” it continued.

Although the Boeing 777 met U.S. FAA and European Joint Aviation Authorities (JAA) airworthiness requirements in force at the time of certification in 1995, “[these] do not appear to address the scenarios identified during this investigation,” said the report. The AAIB cited circumstances “such as the sudden release of accrued ice [in an aircraft fuel system], which could lead to a restricted fuel flow” and consequent loss of engine thrust.

AAIB investigators also recommended that the FAA and the European Aviation Safety Agency (EASA) review current requirements to ensure that aircraft and engine fuel systems will tolerate the potential build-up and sudden release of ice in the fuel-feed system. EASA said it would consider further rulemaking action.