Incident Overview
During a routine powerline patrol, the pilot of a helicopter reported hearing a loud noise, comparable to a gunshot, emanating from directly behind the firewall. Immediately following this sound, the helicopter began to pitch up and roll to the right. The pilot indicated that the aircraft reached a nose-up attitude of approximately 60 degrees and a right roll of about 15 degrees.
Pilot Response
In response to the sudden attitude change, the pilot closed the throttle and lowered the collective, initiating an autorotative descent. Despite the unusual flight characteristics, the pilot found that the lateral cyclic control remained unaffected, allowing him to steer clear of the powerlines. However, the helicopter subsequently crash-landed in the trees.
Reported Failure
The pilot reported that a bolt, part number 20-057-4-15D, had failed in the fore/aft cyclic system. This failure was identified as the component that malfunctioned during the flight.
Investigation Findings
No further details regarding the aircraft type, registration, operator, location, date, time of day, weather conditions, ATC involvement, or occupant injuries were provided in the source. The investigation focused on the reported bolt failure as the primary mechanical issue.