The FAA has published in the Federal Register a revised airworthiness directive for Boeing 777 aircraft equipped with Rolls-Royce engines. The new AD adds further procedures to prevent ice buildup that can clog fuel lines. Airlines have 10 days to comply with the new directive. The new directive affects 56 aircraft in the U.S. fleet, and a total of 228 worldwide.
The British investigation of a Boeing 777 accident at Heathrow in January 2008 found that ice can accumulate in the main fuel tank system of the aircraft at the low fuel temperatures and low-power fuel flows associated with long flights. Investigators found that when the pilot increases power, the increased fuel flow in the tank can cause the ice to break free, which can then block the flow of fuel to the engines.
Initial review of other 777 engine combinations has not revealed the same vulnerability to ice buildup in the fuel lines.
The FAA is working with European aviation safety organizations to consider the implications of this investigation on other aircraft/engine combinations.
