Airworthiness Directives; The Boeing Company Airplanes

We are adopting a new airworthiness directive (AD) for certain The Boeing Company Model 747-200B, 747-200F, 747-300, 747SP, 747-400, and 747-400F series airplanes equipped with Rolls-Royce RB211-524 engines; and certain Model 767-300 series airplanes equipped with Rolls-Royce RB211-524 engines. This AD was prompted by multiple reports of uncommanded thrust reverser unlock events. This AD requires replacing certain relays and relay sockets, and doing wiring changes. For certain airplanes, this AD also requires installing new relay panels, and removing and installing certain components. Additionally, this AD requires, for certain airplanes, accomplishing concurrent actions, which include installing an additional locking system on the thrust reversers and modifying system wiring for in-flight fault indications of the thrust reverser system. We are issuing this AD to prevent an uncommanded thrust reverser deployment during takeoff or in flight, resulting in decreased airplane control and performance, possible runway excursions, and failure to climb.