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The ATSB final investigation report into the crash that killed the two occupants of a Robinson R22 helicopter at Yakka Munga Station in Western Australia, has found that a drive shaft to the main rotor blades failed.

Examination of the shaft revealed that it had failed as a result of a fatigue crack that initiated at a bolt hole in the shaft. Inappropriate procedures, including use of an unapproved sealant, were used when the shaft was last assembled.

During the investigation, the ATSB issued an urgent safety recommendation to the Civil Aviation Safety Authority (CASA) asking for an inspection of the R22 and R44 Australian helicopter fleet. CASA responded by mandating inspections of the shaft assembly to look for signs of damage and to remove those from service that had been assembled using an unapproved sealant.

As a result of the CASA mandated inspections, the use of unapproved sealants was found to be widespread within the Australian R22 helicopter fleet. The Robinson Helicopter Company advised that maintenance documents and training courses would be revised to clarify shaft assembly instructions.

The investigation also found that the survivability of the two occupants may have been adversely affected by the reduced capacity of the seat structures to deform as designed. That was due to the stowage of an excessive amount of baggage and equipment in the underseat baggage compartments.

The full investigation report (200304074) is available from the website, or from the Bureau on request.

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Last update 01 April 2011