What happened
On 15 January 2025, an Airbus Helicopters AS 355 F2, registration G-PDGT, was performing an aerial work positioning flight from Scotland to Ireland West Airport. During the final stages of the flight, the pilot was conducting a hover-taxi toward Taxiway A after being cleared for a visual approach to Runway 26.
While maneuvering at a low altitude, the pilot felt a sudden "kick of yaw" in the aircraft. Upon performing a 90-degree pedal turn to inspect the area, the pilot noticed debris on the runway. After landing at the designated stand and shutting down the engines, the pilot discovered that a portion of the tail rotor driveshaft fairing had detached from the tail boom. The departing fairing had struck the rotating tail rotor blades and the driveshaft, causing mechanical damage. There were no injuries to the single occupant, and the aircraft sustained minor damage.
The investigation
The AAIU examined the aircraft's maintenance history and the physical damage to the components. Investigators found that the tail rotor driveshaft had sustained circumferential scoring, and the tail rotor blades showed signs of impact from the fairing.
Technical analysis of the fairing revealed that while some fasteners remained on the right-hand side of the tail boom, several fasteners on the left-hand side were either missing or had failed. The investigation also reviewed CCTV footage from the departure airport in Scotland, which showed the aircraft departing normally, though it could not confirm the security of the fairing at that time.
Findings
- The separation of the fairing was likely initiated by the loss or improper securing of fasteners on the left-hand side of the component.
- The detachment occurred during a low-altitude maneuver involving complex airflow patterns created by main rotor downwash and increased tail rotor thrust.
- The aircraft was fitted with an incorrect combination of retaining washers and fasteners, which were not in accordance with the manufacturer's Illustrated Parts Catalogue.
- The use of these incorrect washers, while not directly preventing the camlock mechanism from locking, meant the installation did not comply with required technical standards.