Airworthiness Directives; Boeing Model 777 Airplanes

This document publishes in the Federal Register an amendment adopting airworthiness directive (AD) 2005-18-51 that was sent previously to all known U.S. owners and operators of Boeing Model 777 airplanes by individual notices. This AD supersedes an existing AD that applies to certain Boeing Model 777-200 and "300 series airplanes. The existing AD currently requires modification of the operational program software (OPS) of the air data inertial reference unit (ADIRU). This new AD requires installing a certain OPS in the ADIRU, and revising the airplane flight manual to provide the flightcrew with operating instructions for possible ADIRU heading errors and for potential incorrect display of drift angle. This AD results from a recent report of a significant nose-up pitch event. We are issuing this AD to prevent the OPS from using data from faulted (failed) sensors, which could result in anomalies of the fly-by-wire primary flight control, autopilot, auto-throttle, pilot display, and auto-brake systems. These anomalies could result in high pilot workload, deviation from the intended flight path, and possible loss of control of the airplane.