Accident Details
Witnesses reported observing a helicopter flying at a cruising altitude of approximately 200 to 300 feet before it entered a loop-type maneuver. They lost sight of the aircraft near the bottom of the maneuver, after which it crashed. The pilot received serious head injuries and could not recall the events leading up to the accident.
Investigation Findings
Examination of the airframe showed that the transmission and main rotor hub assembly remained partially attached to the airframe through the left and right longitudinal transmission struts. Both left and right vertical struts, as well as both left and right lateral transmission struts, had separated near their attachment points.
A metallurgical examination of the separated components revealed that a fitting assembly (part number 24-61022-6) had failed due to a fatigue crack. Additionally, corrosion was found within the left vertical and lateral (adjustable) transmission struts. Preimpact continuity of the cyclic pitch control was verified.