EASA AD 2019-0109

 
Supersedes an earlier AD requiring inspection of the tail rotor (TR) blades and requires modification as a terminating action. The ADs stem from a report that, following a flight during which the de-icing system of the helicopter was operated, TR blades were overheated with consequent damage after application on ground of alternating-current ground power unit (AC GPU) external power source 115V/400 Hz. Subsequent analysis determined that a power supply box failure (stuck in a “closed” position) caused the uncontrolled power supply to the TR blade de-icing system. In this event, during the preparation for flight with the rotors stationary, the flight crew was able to detect the smell coming from the TR, disconnected the electrical power supply and noticed that the TR blades were damaged by overheat. EASA issued an earlier AD requiring inspection of the TR blades. Since that AD was issued Airbus Helicopters developed a modification to prevent unintended power supply to the TR blade de-icing system and ensuring that the affected power supply remains under full control of the pilot.