What happened
Ground witnesses observed a helicopter executing a normal turn at an altitude of 500 feet above ground level. This maneuver was immediately followed by a violent right turn. During this abrupt rotation, the tail rotor assembly separated from the aircraft, and the main rotor blades were observed coning upwards. The helicopter subsequently entered a near-vertical descent and crashed into the terrain.
The investigation
A thorough examination of the wreckage revealed significant mechanical failures within the tail rotor system. The teetering fork bolt in the tail rotor hub, along with both pitch change links, sustained overload fractures. The fork assembly displayed extensive marks consistent with blade impact. Both tail rotor blades exhibited abrasive signatures on their trailing edges and showed signs of delamination.
The tail skid had separated from the airframe and was fractured at its midspan. Rub marks from a tail rotor blade were visible on the left side of the skid. Metal and chemical analysis indicated that the epoxy bonding material used in the blades had been weakened by a foreign substance. Records showed that both tail rotor blades had been X-rayed and painted 25 flight hours prior to the accident.
Findings
The pilot had not flown a helicopter within the 11 months preceding the accident. Total helicopter flight time was recorded at 50 hours, with only 15 of those hours served as pilot in command.