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Summary

Summary

Earlier on the day of the accident the pilot had experienced a loss of engine power during an attempted takeoff. The problem did not reoccur during a static engine run-up, and the pilot assessed the possible cause as being the hot air temperature. Flight was again attempted later in the afternoon, however, shortly after takeoff at approximately 60 feet above ground level the engine ran roughly, lost all power and produced black smoke. The pilot closed the throttle and attempted to land straight ahead. The aircraft touched down at the end of the strip, entered an overrun area of soft sand and overturned. Examination of the engine revealed that it had been operating on an excessively rich mixture. It was found that an incorrect model carburettor had been fitted, which would have provided too rich a mixture. The engine was being operated using a mixture of mogas and avgas, and the synthetic float in the carburettor was found to be significantly heavier than that specified due to absorption of mogas products. Tests indicated that the resulting high level of fuel within the carburettor float chamber, when combined with pitch changes associated with takeoff and initial climb, caused significant power loss and rough running due to spillage of fuel into the carburettor throat. Simulating the effects of turbulence and vibration exacerbated the power loss, and it is probable that the engine had lost all power due to a rich cut.

 
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