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While operating in a high out of ground effect hover, the pilot heard a change in the engine noise. He noted that the engine torque needles had split by about 60% with the number two engine torque needle reading high. He also noted that the main rotor revolutions per minute (RPM) had increased to maximum (redline). He assessed the problem as a power turbine governor high-side failure and controlled engine parameters by retarding the power lever for number two engine before performing a gentle run on landing in a nearby paddock. The air pressure line (Pr line) between the power turbine governor and the fuel control unit was found to have broken in the sleeve near the pipe flare where it was attached to the power turbine governor. The broken pipe allowed pressurised air to escape, thereby causing a governor high side failure. The company chief engineer determined that the stainless steel pipe broke because it was misaligned at the fitting to the fuel control unit. This placed the pipe under stress which eventually caused it to break near the other end fitted to the power turbine governor.
Download Final Report
[ Download PDF: 12KB]
General details
Date: 17 May 1993 Investigation status: Completed 
Time: 8:30 EST  
 Investigation type: Occurrence Investigation 
 Occurrence type: Abnormal engine indications 
Release date: 18 May 1993 Occurrence class: Technical 
Report status: Final Occurrence category: Incident 
Aircraft details
Aircraft manufacturer: Aerospatiale Industries 
Aircraft model: AS.355F1 
Aircraft registration: VH-HRA 
Sector: Helicopter 
Damage to aircraft: Nil 
Departure point:Port Melbourne Helipad Vic.
Destination:Port Melbourne Helipad Vic.
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Last update 16 November 2015