Aviation safety investigations & reports

Hughes 269C, VH-THY, 5km East of Theda Station, 50 South of Kalumburu WA, 1 May 1986

Investigation number:
Status: Completed
Investigation completed


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The pilot was engaged in mustering operations and was attempting transition from a low forward speed to an out of ground effect hover in order to turn a breakway beast. As he approached the hover, the helicopter experienced a sudden partial power failure. The pilot maintained the aircraft heading, lowered the collective lever and attempted to gain some forward airspeed. In the attempted landing with partial power, the helicopter struck the ground heavily and its main rotor blades hit a small sapling. The forced landing was made in light downwind conditions. Investigation revealed that the No 2 cylinder exhaust valve had failed in fatigue and the valve seat and retaining cap had failed in overload. Further testing indicated that the exhaust valve had been subjected to higher than normal operating temperatures which would have contributed to the premature failure of the valve.

Download Final Report
[Download  PDF: 22KB]
General details
Date: 01 May 1986   Investigation status: Completed  
Time: 1345    
Location: 5km East of Theda Station, 50 South of Kalumburu    
State: Western Australia    
Release date: 01 May 1987   Occurrence category: Accident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Hughes Helicopters  
Aircraft model 269  
Aircraft registration VH-THY  
Type of operation Aerial Work  
Sector Helicopter  
Damage to aircraft Substantial  
Departure point Theda Station WA  
Departure time 1345  
Destination Theda Station WA