AD Proposed for Rockwell Collins Transponders

The FAA proposes to adopt a new airworthiness directive for certain Rockwell Collins TDR-94 and TDR-94D mode-S transponders. The AD was prompted by instances of the transponders not properly responding to mode-S only all-call interrogations when the airplane transitioned from a ground to airborne state. This proposed AD would require inspecting the setting of the airplane type code category strapping and require either modifying the airplane type code category setting or installing the software upgrade to convert the affected transponders to the new part number. The FAA is taking comments until July 7.