What happened
The incident occurred during the takeoff phase of a touch-and-go operation. At an altitude of approximately 15 feet above ground level, the engine unexpectedly reduced to idle power. In response to this loss of thrust, the pilot initiated a left turn and directed the aircraft toward a nearby field for an emergency landing. The impact with the ground resulted in the collapse of the landing gear.
The investigation
A thorough examination of the wreckage was conducted to determine the mechanical cause of the engine failure. Investigators discovered that the carburetor was not securely attached to its mounting points; instead, it remained suspended solely by the throttle and mixture control cables. Upon closer inspection, the mixture control lever arm on the carburetor was found positioned in the full lean setting.
Standard procedure requires the carburetor mixture control to be wired to remain in the full rich position to prevent accidental leaning. However, the safety wire was discovered to be attached only to the bolts securing the mixture control plate cover, rather than the control mechanism itself. This improper wiring configuration allowed the mixture control to move freely from its intended setting.
Findings
The investigation could not definitively determine whether the mixture control had been moved to the full lean position prior to the takeoff or if it shifted during the accident sequence. Regardless of when the shift occurred, the lack of positive retention for the mixture control allowed the engine to run in a lean condition, leading to the idle event at low altitude.
Safety message
Proper installation and verification of safety wiring on critical engine controls are essential to prevent unintended changes in engine operation during flight.