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Final Report

Summary

What happened

Late in the afternoon on Sunday 19 July 2015, an amateur-built Stoddard Hamilton Glasair SH-2FT two-seat aeroplane, registered VH-HRG and operated in the Experimental category, was seen flying due north, consistent with the downwind leg of a circuit for landing at Wedderburn Airport, New South Wales.

Witnesses stated that they heard the aircraft’s engine surge twice and then silence, prior to hearing the aircraft collide with wooded terrain about 900 m north of the runway threshold. No witness reported seeing the aircraft turn onto the base leg or final approach, nor the aircraft collide with terrain.

The pilot sustained serious injuries, the passenger was fatally injured and the aircraft was destroyed.

What the ATSB found

The ATSB found that during the turn onto final approach to land, the aeroplane’s engine ceased operating. Following the loss of power, the pilot was unable to control the aircraft’s descent to an appropriate forced landing area before colliding with the ground.

The ATSB also found that the loss of power was probably due to carburettor icing. No defects were identified that would have precluded normal operation of the aircraft or its engine prior to the accident. However, the environmental conditions at the time were conducive to serious carburettor icing at all power settings. The pilot reported using a low power setting during the downwind leg of the circuit to slow the aircraft down and did not use the carburettor heat system.

There was insufficient evidence to support other possible hypotheses for the aircraft’s loss of control, such as an aerodynamic stall as a result of aircraft handling.

Safety message

The ATSB advises pilots of aircraft fitted with a carburettor to check the forecast weather conditions affecting their operations, and consider the risk of carburettor icing prior to each flight. Pilots should be aware that carburettor icing can form over a wide range of outside air temperatures and relative humidity and understand the importance of following aircraft manufacturer guidelines regarding the use of carburettor heat. Further, they should be mindful that certain flight conditions, such as lower engine power settings, may increase the risk of ice accumulating in the engine’s carburettor.

The Civil Aviation Safety Authority’s Carburettor icing probability chart provides helpful guidance for pilots to determine carburettor icing probability before flying. The chart is available at www.casa.gov.au.

Photograph of VH-HRG
VH-HRG
Source: NSW Sport Aircraft Club

The occurrence

Context

Safety analysis

Findings

Sources and submissions

Appendices

 
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