Summary
The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to certain serial numbers (SN's) of NARCO Avionics Inc. AT150 transponders. This proposal would require modification to the transponder by adding a resistor and transistor to the circuit board. This proposal is prompted by reports of AT150 transponders not recognizing and responding properly to Mode S interrogations from Mode S ground stations and Traffic Alert and Collision Avoidance System (TCAS-II) airborne equipment. The actions specified by the proposed AD are intended to prevent loss of aircraft airspace separation and the possibility of mid-air collision.