Summary
The FAA proposes to adopt a new airworthiness directive (AD) for certain Honeywell COM units and transponders, installed on but not limited to certain transport category airplanes. This proposed AD would require a revision to the Normal Procedures section of the Airplane Flight Manual to advise the flightcrew to check the status of the transponder after changing the air traffic control (ATC) code. This proposed AD would also require replacing certain identification plate(s) with new plate(s), testing certain COM units or transponders as applicable, and corrective action if necessary. For certain airplanes, this proposed AD would require replacing the transponders of certain COM units with new or modified transponders. For certain other airplanes, this proposed AD would require installing a modification into certain transponders. This proposed AD results from the transponder erroneously going into standby mode if the flightcrew takes longer than five seconds when using the rotary knob of the radio management unit to change the ATC code. We are proposing this AD to prevent the transponder of the COM unit from going into standby mode, which could increase the workload on the flightcrew and result in improper functioning of the traffic alert and collision avoidance system.