An ex-US military helicopter being used for agricultural work crashed in Southland last year because a critical component failed, a report said yesterday.
The Transport Accident Investigation Commission (TAIC) report said the Bell/Garlick UH1B Iroquois, manufactured 40 years earlier, shed a rotor blade while flying from Waikawa Valley in southernSouthland to Gore on April 23 last year.
It then broke up and crashed from 500 feet southeast of Wyndham.
The pilot and sole occupant, Southlander Tony Bell, 48, died on impact. The report said the crash was unsurvivable.
Mr Bell had logged about 3780 hours flying at the time of his death, 566 hours on the type of helicopter in which he was killed.
The TAIC said the accident was caused by the fatigue failure of a tension-torsion (TT) strap.
The TT straps hold the main rotor blades in the rotor hub.
"The fatigue cracking had probably been initiated by an unreported rotor overspeed event."
The report noted two safety issues:
* The need for pilots to understand the importance of reporting a rotor-overspeed incident.
* The need for US Federal Aviation Administration (FAA) and New Zealand Civil Aviation Authority (CAA) airworthiness personnel and licensed maintenance engineers to "recognise and respond to documented improper identification of critical finite-life components such as TT straps".
The report said safety recommendations targeting these issues had been sent to the chiefs of both organisations.
The accident investigation showed the helicopter was on its way to Gore airfield where Mr Bell was to meet the chief pilot and chief engineer of the aircraft's owners, BA and JC Emeny Ltd (Helicopter Services) based in Inglewood, Taranaki.
Mr Bell had reported "vertical bounce" or vibration from the main rotor.
But the report said no overspeed event involving the Iroquois had been reported or logged and it was possible the pilot did not appreciate the significance of a rotor overspeed.
The TAIC noted that TT straps on the crashed aircraft had no identification markings and thus accurate records of their time in service could not be determined.
It was "surprising" that the parties involved with the Iroquois - the US firm which refurbished the helicopter in 1994 after its military life, the FAA, the CAA, the NZ operator and the chief engineer who reassembled the aircraft here - overlooked or missed "this documented inadequacy".
