What happened
On the afternoon of 20 March 2008, an Agusta A109E helicopter, registration EI-SBM, was conducting a private flight under Special Visual Flight Rules (SVFR). The aircraft was traveling from Celtic Heliport in Co. Dublin toward Weston Airport in Co. Kildare. The pilot was the only person on board.
During the flight, Dublin Air Traffic Control provided instructions for the pilot to navigate via the Dublin VOR, Ashbourne, and Dunshaughlin, maintaining an altitude below 1,000 feet. While approaching Dunshaughlin, the pilot notified controllers of technical difficulties and subsequently declared a "MAYDAY" to initiate an emergency landing. This was the final communication received from the aircraft.
The pilot reported hearing a loud bang originating from the rear of the helicopter, followed by an uncontrollable turn to the starboard side. In response to the emergency, the pilot executed an autorotation, shut down both engines, and deployed the undercarriage. The helicopter subsequently crash-landed in soft, boggy ground just east of Dunshelleigh, where it overturned on its left side. The impact resulted in the aircraft being destroyed, though no fire occurred. The pilot, who suffered serious injuries, managed to exit the wreckage and remained on the ground until emergency responders arrived to airlift him to a hospital in Drogheda.
The investigation
Following the emergency declaration, investigators from the AAIU arrived at the site to conduct a technical examination. The investigation focused on the mechanical state of the aircraft and the circumstances leading to the loss of directional control.
Findings
Investigators discovered a foreign object made of cloth lodged within the tail rotor driveshaft tunnel. This object had become entangled in the driveshaft between the first and second bearings. The examination revealed that the driveshaft had failed just in front of the second bearing, which effectively disconnected the drive mechanism to the tail rotor. Initial findings suggest that the presence of this cloth material was the primary cause of the shaft failure.