Robinson Helicopter R44 N452JM accident near San Juan, Puerto Rico

Probable cause

The detachment of the forward left servo control tube upper rod end attachment bolt during a hover due to separation of its retaining nut for undetermined reasons.

NTSB analysis

After a 1.5-hour flight, while hover taxiing, the pilot initiated a turn to the left when the helicopter pitched up and rolled left, striking the main rotor blades against the ground and eventually coming to rest on its left side. The Puerto Rico Port Authority then moved the helicopter and cleaned up all of the scattered helicopter parts and debris prior to the arrival of a Federal Aviation Administration (FAA) inspector and without any photo documentation of the wreckage. The FAA inspector subsequently took photographs of the wreckage that included the forward left cyclic servo control (push-pull) tube attachment point on the non-rotating swashplate. The control tube was not attached and the swashplate attachment ear had no corresponding attachment hardware. In addition, the control tube rod end was separated from the top of the tube in overload. A search of the wreckage and the crash site by the FAA inspector did not produce the rod end, nor did a subsequent court-ordered search. A detailed examination of the helicopter revealed that the interior bore of the left lateral servo attachment ear had multiple scoring and impact marks consistent with the dimensions and spacing of the attachment bolt threads. The marks also indicated that the rod end attachment bolt had been forcibly pivoted while backing out of the hole, which likely occurred because the retaining nut was missing. During the helicopter's most recent annual inspection the left lateral servo was removed and replaced; however, neither the inspection nor the replacement of the servo required disconnection of the upper servo control tube rod end from the swashplate attachment ear. The pilot's operating handbook required the pilot to ensure that the flight control rod ends were "free without looseness," and that all fasteners were "tight" during preflight inspections. However, it is unknown whether the retaining nut was missing before the flight or if it came off in flight.

Text from the NTSB. Open the NTSB docket for ERA09LA051 for the full record.