Summary
We propose to adopt a new airworthiness directive (AD) for certain Trig Avionics Limited TT31, Avidyne Corporation AXP340, and BendixKing/Honeywell International KT74 Mode S transponders. This proposed AD was prompted by the discovery that the retaining cam that engages in the mounting tray may not withstand g-forces experienced during an emergency landing. This proposed AD would require a one-time inspection of the transponder installation to determine if this is a conventional aft-facing installation, and depending on the findings, removal of the affected transponder for modification. We are proposing this AD to address the unsafe condition on these products.