G-BUGT’s departure from Runway 35 was delayed because the runway was occupied, and the pilot applied carburettor heat while waiting. When the runway was clear, the pilot lined up and applied full throttle without stopping. At approximately 150 to 200 ft, the pilot felt a complete loss of power and executed a forced landing. The aircraft touched down close to the field boundary. The pilot “attempted a hop” through a gap but the wings struck bushes. After stopping, the pilot noticed that the carburettor heat was still selected ON.
Inspection of the aircraft engine and associated systems revealed no faults which would explain the power loss. Tests of carburettor heat effectiveness on two other Slingsby Ventures indicated that full carburettor heat resulted in a drop of up to 600 rpm, and extended use in flight resulted in rough running and climb was not possible. The tests did not replicate a total loss of power. Full power was always restored when the carburettor heat was returned to cold.
The pilot commented that he should have repeated the pre-takeoff checks immediately before takeoff, which would have revealed that the carburettor heat was on. Checking the rpm achieved during the takeoff roll may help to identify an engine that is not performing as required.
A correction was issued concerning this report prior to publication. Details of the correction can be found in the downloadable report below and the May 2019 Bulletin.
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