What happened
On 16 July 2022, an Alouette II helicopter, registration N577AG, was being repositioned at Newcastle Airfield, Co. Wicklow. The pilot, intending to move the aircraft to a different location on the airfield, performed a pre-flight inspection and started the engine using a power pack. After lifting off to a height of approximately 20 feet, the aircraft began a controlled turn to establish an easterly heading.
Approximately 33 seconds into the flight, the pilot heard a loud bang, described as something snapping or breaking. Immediately following this sound, the helicopter experienced an uncommanded leftward yaw and a nose-down attitude. The pilot attempted to recover by pulling the cyclic control stick fully back, but the aircraft continued to descend and roll to the right. The main rotor blades struck the ground, and the tail boom separated from the main fuselage. The aircraft rotated approximately 450 degrees while the engine remained running. The pilot sustained serious injuries but was able to evacuate the cockpit once the rotors stopped. A small grass fire ignited at the site but was quickly extinguished by bystanders.
The investigation
Investigators from the AAIU reviewed CCTV footage from the airfield, which captured the entire sequence from engine start to impact. The investigation also included interviews with the pilot and two witnesses, including a medical professional who assisted the pilot.
Technical examination of the wreckage at the AAIU facility revealed that the helicopter had not undergone certified maintenance since 2007 and lacked current airworthiness certification. While the control cables themselves were intact, several pulleys on the tail boom were not rotating freely. Notably, the nuts and bolts that secure the universal joint to the main gearbox output flange were missing from the wreckage.
Findings
- The sudden leftward yaw and subsequent loss of control were caused by a loss of drive to the tail rotor.
- This loss of drive likely occurred because the fasteners (nuts and bolts) securing the universal joint to the gearbox output flange became loose and eventually failed or migrated.
- The pilot's use of a four-point harness likely mitigated the severity of the injuries sustained during the impact.
- The aircraft had no record of certified maintenance since October 2007 and was operating without an active airworthiness certificate at the time of the accident.