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The helicopter was in a steady cruise at 80 kts at 1,500 ft above ground level when the pilot heard a loud bang. He immediately initiated auto-rotation and believed that there had been a failure of the tail rotor drive. The pilot attempted a landing in the nearest clear area but the nature and slope of the terrain coupled with some rotation of the helicopter resulted in it rolling over and sustaining severe damage during the landing. Examination of the helicopter revealed that the intermediate flex plate failed. This flex plate consists of the front and rear yokes plus the flex plate itself, all joined by four bolts. The examination found that one of the two front lugs was missing. The adjoining flex plate lug was present and bent forward. The bolt joining the missing front yoke lug to the adjoining flex plate lug was also not present. Neither the bolt nor the front yoke lug were found at the accident site. The hole in the flex plate lug, opposite the missing front yoke lug, was worn and enlarged suggesting that, after the bolt was liberated, the shaft's axis of rotation changed. Such an event would have led to failure of the tail rotor drive and given the symptoms described by the pilot.
Download Final Report
[ Download PDF: 11KB]
General details
Date: 02 April 1997 Investigation status: Completed 
Time: 6:30 EST  
 Investigation type: Occurrence Investigation 
 Occurrence type: Forced/precautionary landing 
Release date: 08 August 1997  
Report status: Final Occurrence category: Accident 
Aircraft details
Aircraft manufacturer: Robinson Helicopter Co 
Aircraft model: R22 BETA 
Aircraft registration: VH-DBQ 
Sector: Helicopter 
Damage to aircraft: Substantial 
Departure point:Bungobine Station
Destination:Havilah Station
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Last update 28 October 2014