On May 4, 1990, a Hughes 369C (registration N9219F) operated by Alex Air was involved in an aviation accident near Kahului, HI. Investigators recorded the probable cause as: The pilot's failure to maintain clearance from the tug vehicle and its attached light pole while positioning the helicopter over the wheeled landing platform. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter's tail boom struck a light pole attached to a tug vehicle while the pilot was positioning the aircraft over a wheeled landing platform after disembarking passengers.
What happened
The pilot was maneuvering a helicopter over a wheeled landing platform following the disembarkation of passengers. During this phase, the pilot executed a hovering turn directly above the platform. A tug vehicle had been positioned in close proximity to the landing area, with a six-foot light pole attached to its front. As the helicopter rotated, the tail boom made contact with the light pole. The impact caused the tail rotor gearbox and blades to separate from the tailboom.
The investigation
The primary mechanical failure resulted from the external collision between the aircraft's tail structure and the stationary object on the ground vehicle. No further mechanical anomalies were noted in the provided narrative.
Findings
The accident was caused by the pilot's decision to position the helicopter too close to the tug vehicle, which had a protruding light pole. The proximity of the ground support equipment to the landing platform created an obstacle that was not adequately accounted for during the hovering maneuver.
Probable cause
The pilot's failure to maintain clearance from the tug vehicle and its attached light pole while positioning the helicopter over the wheeled landing platform.