Airworthiness Directives; Various Transport Category Airplanes Equipped With Certain Honeywell Air Data Inertial Reference Units

This amendment adopts a new airworthiness directive (AD) that is applicable to various transport category airplanes equipped with certain Honeywell air data inertial reference units (ADIRU). This action requires inspection of a failed ADIRU to determine its modification status, and replacement of an unmodified failed ADIRU with a serviceable ADIRU. This action also provides for optional terminating action for the requirements of the AD. This amendment is prompted by reports of dual critical failures of inertial reference units on ADIRU's during flight. The actions specified in this AD are intended to prevent loss of the main sources of attitude data, consequent high pilot workload, and a significant increase in the likelihood of pilot error.