Summary
This document proposes to adopt a new airworthiness directive (AD) that would apply to certain Honeywell, Inc. part number (P/N) HG1075AB05 and HG1075GB05 inertial reference units (IRU) that are installed on aircraft. This proposed AD would require you to inspect the affected IRU's for proper function and remove the IRU either immediately or at a certain time depending on the result of the inspection. This proposed AD is the result of a report that these IRU's may not function when using backup battery power in certain installations. The actions specified by this proposed AD are intended to ensure the correct transition of the IRU to backup battery power upon the loss of primary power. Failure of an IRU to transition to backup battery power could result in loss of attitude, heading, and position reference and lead to the pilot making flight decisions that put the aircraft in unsafe flight conditions.