Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 777-200 and -300 series airplanes. This proposed AD would require revising the airplane flight manual to provide the flightcrew with new ground procedures for shedding core ice during long taxi periods in freezing fog. For airplanes unable to perform the shedding procedure after prolonged taxiing in freezing fog, this proposed AD would require certain investigative and corrective actions. This proposed AD results from reports of engine surges and internal engine damage due to ice accumulation during extended idle thrust operation in ground fog icing conditions. We are proposing this AD to prevent internal engine damage due to ice accumulation and shedding, which could cause a shutdown of both engines, and result in loss of control of the airplane.