Airworthiness Directives; Boeing Model 777-200 and -300 Series Airplanes Equipped With Rolls-Royce Model RB211-TRENT 800 Series Engines

We are adopting a new airworthiness directive (AD) for certain Boeing Model 777-200 and -300 series airplanes. This AD requires revising the airplane flight manual to include in-flight procedures for pilots to follow in certain cold weather conditions and requires fuel circulation procedures on the ground when certain conditions exist. This AD results from a report of uncommanded reduction in thrust on both engines because of reduced fuel flows. We are issuing this AD to prevent ice from accumulating in the main tank fuel feed system, which, when released, could result in a restriction in the engine fuel system. Such a restriction could result in failure to achieve a commanded thrust, and consequent forced landing of the airplane.