EASA 2018-0247

Requires a one-time inspection of the transponder installation to determine whether it involved a conventional installation, and removal and modification, if necessary. The AD stems from the discovery that the retaining cam did not meet approved design criteria for crash safety shock in the aft direction (20g sustained). This was due to an uncontrolled deviation in the manufacturing process of the retaining cam by the part manufacturer. The retaining cam is a small nylon part that engages in the mounting tray when the transponder is installed into the aircraft. Tests using affected retaining cam showed that the transponders meet RTCA/DO-106G Section 7.0 operational shocks and crash safety impulse and sustained tests for all directions, except the aft direction. Consequently, units installed with a control panel orientation that is not opposite to the direction of flight may not withstand g-forces experienced during an emergency landing.