Aviation safety investigations & reports

Beech 58 Baron, VH-WBR, Cairns QLD, 20 July 1989

Investigation number:
Status: Completed
Investigation completed


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The pilot reported that soon after takeoff from Cairns the right engine rapidly lost oil pressure accompanied by a rise in the oil temperature. There was also a noticeable drop in manifold pressure and engine rpm. The pilot feathered the propeller and advised the tower of his intention to returned to Cairns where a single engine landing was carried out. A local Licensed Aircraft Maintenance Engineer (LAME) was then engaged to investigate and rectify the defect. After checking the oil quantity and completing a visual inspection of the engine bay the LAME carried out a ground run to verify the extent of the oil pressure loss. All engine parameters including oil pressure and temperature indicated normal during the prolonged ground run. The LAME then advised the pilot that he considered the aircraft to be serviceable and explained to him that the probable cause of the pressure loss was that a piece of carbon had become temperarily lodged under the seat of the oil pressure relief valve. No further "trouble shooting" was carried out by the LAME. Soon after takeoff on the next flight the pilot noticed that the right alternator was not showing a charge. This defect was entered on the maintenance release on arrival in Townsville. The subsequent inspection of the aircraft discovered that the alternator drive "clutch spring" was badly distorted and had caused extensive scoring damage to the internal crankcase casting. The metal filings produced by this scoring action had contaminated the engine oil system. The extent of this contamination necessitated a bulk strip of the engine and accessories. It was found that the crankshaft all main bearings conrod bearings oil pump and oil pump housing had been substantially damaged.

Download Final Report
[Download  PDF: 24KB]
General details
Date: 20 July 1989   Investigation status: Completed  
Time: 1605    
Location: Cairns    
State: Queensland    
Release date: 08 September 1989   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Beech Aircraft Corp  
Aircraft model 58  
Aircraft registration VH-WBR  
Serial number TH 71  
Type of operation Charter  
Damage to aircraft Nil  
Departure point Cairns QLD  
Departure time 1600  
Destination Townsville QLD