On October 13, 2000, an Aerospatiale AS350-BH (registration N532BH) operated by Blue Hawaiian Helicopters was involved in an aviation accident near Hilo, HI. Investigators recorded the probable cause as: Inadequate maintenance by the helicopter manufacturer during manufacture, which installed skins of inadequate thickness on the tail boom. A factor in the accident was the failure of the manufacturer's quality control system to detect the inadequate thickness. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 2 related events involving the same aircraft type or operator are linked below.
A helicopter's tail boom bent downward after a practice hovering autorotation landing. The pilot felt a component failure 2 seconds after touchdown, with vibrations and failure indications. Postaccident inspection revealed the tail boom skin thickness was 0.025 inches, below the 0.032 inches specified in the repair manual.
Accident Details
A helicopter experienced a tail boom failure during landing following a practice hovering autorotation. The pilot reported that the accident occurred after the third hovering autorotation landing of the session. He stated that the touchdown was acceptable and would have met check ride criteria. Approximately 2 seconds after touchdown, an "obvious component failure" was felt throughout the airframe, accompanied by severe vibrations and "audible and physical indications" of failure.
Pilot Observations
After exiting the aircraft, the pilot expected to find a problem in the main rotor head and was surprised to discover the tail boom bent downward at the midpoint.
Postaccident Examination
A postaccident examination of the helicopter revealed that the tail boom was fabricated from skins with a thickness of 0.025 inches, as opposed to the skin thickness of 0.032 inches identified in the structural repair manual. The helicopter records showed that the tail boom was originally installed on the new helicopter at the factory and had accumulated 14,053 hours in service.