Summary
We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-200B, 747-300, 747-400, 747-400D, 747-400F series airplanes, and Model 767 series airplanes, powered by General Electric (GE) CF6-80C2 engines. This proposed AD was prompted by reports of failure of the electro-mechanical brake flex shaft (short flexshaft) of the thrust reverser actuation system (TRAS). This proposed AD would require replacing the short flexshaft on each engine with a new short flexshaft, testing of the electro-mechanical brake and center drive unit (CDU) cone brake to verify the holding torque, and performing related investigative and corrective actions if necessary. We are proposing this AD to prevent an uncommanded in-flight thrust reverser deployment and consequent loss of control of the airplane.