History of Flight
The pilot of a Robinson R22 Beta helicopter, together with a passenger acting as a spotter, was engaged in a mustering operation at a remote cattle station. The spotter reported that while transiting to another paddock, at a height of approximately 200 ft above ground level, the helicopter developed a lateral shudder. The shudder intensified and the pilot rapidly lost control of the helicopter as it shuffled to the right. The helicopter then impacted the ground in a nose down, slight right-bank attitude, with little forward speed. A member of the support ground team nearby heard the impact and went to the scene. The pilot and observer had egressed the helicopter and were found lying on the ground forward of the cockpit. The pilot died while enroute to hospital.
Wreckage examination
The helicopter fuselage was extensively damaged, and the tail boom severed. The fuselage sustained a downward and forward crushing of the right side of the cockpit area, and as a result the pilot received fatal injuries. The main rotor mast assembly separated in flight, damaging the engine firewall and both fuel tanks. Only one main rotor blade remained attached to the main rotor hub. That blade displayed impact damage; the result of striking and severing the tailboom. The other main rotor blade displayed a fracture at the blade root fitting. The matching separated main rotor blade section was discovered 105 metres from the crash site and had incurred minimal impact damage. The location of the blade suggested an in-flight separation. The main rotor mast assembly had failed in overload resulting from the out-of-balance condition experienced following separation of the blade.
The right fuel tank was found 20 metres from the fuselage and had minor impact damage. Approximately one litre of fuel was recovered from the tank. The tank had separated from the helicopter in flight. The tail rotor assembly with the severed tailboom attached was found 34 metres from the accident site. The tail rotor blades, and hub were intact. Both tail rotor blades displayed side compression bending loads. There was evidence of low tail rotor RPM at impact.
Weather
Witnesses reported the weather as unlimited visibility with some scattered cloud cover. Weather was not considered a factor in the circumstances of the accident.
Helicopter history
The helicopter had recorded 2,124.6 hours time in service (TIS). That total flight time was derived from the helicopter hour meter, as the pilot's logbook and helicopter maintenance release were incomplete. The last flight entered in the pilot's logbook was on 2 July 2000, 27 days prior to the accident. The last entry on the helicopter maintenance release was 4 July 2000, at 2,102.4 hours TIS, 25 days before the accident. Those were the hours at the time of release to service following a 100-hour inspection, completed on the same date and TIS. No flight entries had been made from that date until the time of the accident.
Helicopter operations
There was anecdotal evidence from witnesses who were familiar with the operation of the helicopter that suggested it might have been operating more hours than was being documented. A review of company and helicopter records was completed to substantiate helicopter operating hours. That review comprised analysis and comparison of company customer flight time and fuel invoices and helicopter spares usage versus recorded helicopter flight time. That evidence suggested the helicopter operating hours were being under-reported and supported the anecdotal evidence of the witnesses.
Personnel information
The pilot held a Commercial Pilot's Licence (Helicopter), R22 and R44 helicopter endorsements, and a valid class one medical certificate. He had recorded 662.5 hours total time in helicopters as of the last entry in his logbook. Of that total, 660.5 hours were in that type of helicopter. In the 90 days prior to the accident he had logged 95.6 hours flying that specific helicopter. The pilot's last flight review was completed on 9 June 2000. The pilot completed an R22 Helicopter Ground Awareness, Safety Awareness, and Flight Check course on 26 January 1997. He also completed a Low Flying training course on 11 June 1998.
Service life of the main rotor blade
The recorded TIS of the separated main rotor blade part number A016-2, serial number (S/N) 9278B, revision AG, derived from helicopter logbook entries, was 1,995.5 hours. The logbook annotated that the blade had accumulated 1,299.9 hours TIS when installed on 20 May 1998. The mandatory retirement time of the main rotor blade was 2,200 hours TIS. The manufacturer determined the retirement time/service life of the R22 blades using a formula developed from fatigue testing.
Related occurrence
Occurrence 199000089
A Robinson R22 helicopter involved in mustering was transiting from one parking area to a more open area to board a passenger. At an altitude of approximately 300 ft, witnesses heard a sharp crack and all engine and rotor noise ceased. The helicopter descended at a steep angle and impacted the ground. Witnesses removed the occupants before the post crash fire, which consumed the wreckage. Both occupants received fatal injuries. The on-site investigation revealed an in-flight separation of one main rotor blade. Analysis of the failed blade revealed a fatigue crack of the main rotor blade root fitting. It was established that the retirement time of the main rotor blade had been exceeded by a minimum of 257.2 hours. It was believed the hours entered in the helicopter logbook did not reflect the actual operating hours.
Safety action following occurrence 199000089
As a result of the investigation into Occurrence 199000089, a manufacturing anomaly of the R22 main rotor blade was discovered which related to load transfer through the rib root fitting. In April 1991, the Australian Transport Safety Bureau (then known as the Bureau of Air Safety Investigation) issued three recommendations:
1) Recommendation B/905/1021 suggested a review of the retirement time of the blade.
Civil Aviation Authority response to Recommendation B/905/1021:
A review was completed using information based on the true service time of the failed blade. The Civil Aviation Authority (CAA) released Airworthiness Directive AD/R22/31 in June 1990, mandating a 1,000-hour retirement time of the R22 main rotor blades until an acceptable method of inspection of the blade be developed to detect cracks in the rib root fitting. In June 1990, CAA Airworthiness Directive AD/R22/31 amendment 1 was released, increasing the retirement times to 1,500-hours pending the development of the inspection procedures.
2) Recommendation B/905/1021 also suggested that the CAA and the manufacturer develop an inspection technique for the blade to detect progressive fatigue failure of the in the area of the rib root fitting.
Additional Civil Aviation Authority response to Recommendation B/905/1021:
CAA Airworthiness Directive AD/R22/31 amendment 2 was released in March 1991, mandating an eddy current inspection for all blades which had exceeded 1,500 hours service life, with recurring inspection every 200 hours thereafter. That directive did not address blade part numbers and was addressed to all models fitted with main rotor blades up to and including S/N 5493.
3) Recommendation B/905/1021 furthermore suggested that the helicopter manufacturer address the load transfer anomalies.
Robinson Helicopter Company response to Recommendation B/905/1021:
The manufacturer reviewed their procedures and made process specification revisions to eliminate those anomalies.
The accident main rotor blade (S/N 9278B) had not been eddy current inspected, as the directive was not applicable by serial number. The procedural changes and process specification revisions implemented by the manufacturer eliminated the requirement for the eddy current inspection.
