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The pilot was approaching the rear of a herd of cattle when he attempted to climb the aircraft. As he raised the collective control the engine RPM started to decrease. There was no suitable landing site below the helicopter so the pilot was forced to manoeuvre the aircraft around several trees to get to a suitable landing area. As he flared the aircraft for a landing the tail rotor contacted the ground and the main rotor severed the trunks of a tree and two saplings. The helicopter yawed to the left and slid sideways collapsing the left landing skid. The throttle control shaft output assembly, within the throttle control cambox had become dislodged, depriving the pilot of throttle control. The resultant freeplay within the throttle control system allowed the throttle butterfly to return to the idle position. The bearings and sleeves within the cambox are secured at manufacture by roll staking, which is considered to be the superior method for securing these components. However, the manufacturers maintenance instructions makes no mention of the method of securing the bearings and sleeves in the cambox. These components in the subject aircraft had been overhauled and were retained by the use of adhesive, which subsequently failed.

Download Final Report
[ Download PDF: 22KB]
General details
Date: 31 May 1987 Investigation status: Completed 
Time: 1400  
Location:Mountain Valley Station Investigation type: Occurrence Investigation 
State: Northern Territory  
Release date: 08 September 1987  
Report status: Final Occurrence category: Accident 
 Highest injury level: None 
Aircraft details
Aircraft manufacturer: Bell Helicopter Co 
Aircraft model: 47 
Aircraft registration: VH-SJI 
Serial number: 6632 
Type of operation: Aerial Work 
Sector: Helicopter 
Damage to aircraft: Substantial 
Departure point:Mountain Valley Station NT
Departure time:1400
Destination:Mountain Valley Station NT
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