Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Boeing Model 777-200 and -300 series airplanes. This proposed AD would require modification of the operational program software (OPS) of the air data inertial reference unit (ADIRU). This proposed AD is prompted by a report of the display of erroneous heading information to the pilot due to a defect in the OPS of the ADIRU. We are proposing this AD to prevent the display of erroneous heading information to the pilot, which could result in loss of the main sources of attitude data, consequent high pilot workload, and subsequent deviation from the intended flight path.