EASA 2023-0197

Requires a one-time inspection of the axial displacement of the tail rotor drive shaft and any necessary corrective action. This AD also provides additional requirements for installation of tail rotor drive shafts. Prompted by reported occurrences of ruptured/deformed flexible couplings. Subsequent investigations have determined that a flexible coupling installed with high axial displacement develops increased stresses and friction between its sheets. If not detected and corrected, this condition could lead to cracks and extensive deformation of flexible couplings and consequent high vibration of the tail rotor drive shaft, possibly resulting in reduced control of the helicopter.