Airworthiness Directives; The Boeing Company Airplanes

We propose to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 747-400, 747-400D, and 747-400F series airplanes; Model 757 airplanes; and Model 767 airplanes. This proposed AD was prompted by reports of uncommanded autopilot engagement events resulting in incorrect stabilizer trim adjustment during takeoff. This proposed AD would require, depending on the model/configuration for Model 747 airplanes, installing an on-ground stabilizer autotrim inhibit system, doing routine functional testing of the automatic stabilizer trim inhibit system and corrective actions if necessary; for Model 757 airplanes and Model 767 airplanes, installing relays and related wiring to open and close the flight control computer (FCC) analog output that controls the stabilizer trim adjustment, doing routine functional testing of the automatic stabilizer trim inhibit system, and corrective actions if necessary; and for Model 767-300, and -300F series airplanes, installing new operational program software (OPS) into the FCCs. We are proposing this AD to prevent stabilizer mistrim, which could result in a high-speed rejected takeoff and runway overrun, or reduced controllability of the airplane after takeoff due to insufficient pitch control.