Accident Sequence
While on final approach for landing, the pilot advanced the throttle to adjust the approach path. The engine subsequently lost power, and the aircraft impacted the ground short of the runway. Upon impact, the aircraft flipped inverted.
Investigation
After the accident, the engine was test run and found to perform to manufacturer's specifications. However, examination of the carburetor airbox, which regulates carburetor heat, revealed that it had been improperly repaired. The repair involved redrilling a hole in the control arm attachment point. Due to the damage sustained by the aircraft, investigators could not determine what effect this improper repair had on the operation of the carburetor heat control.
Findings
The carburetor airbox control arm attachment point had been redrilled as part of a previous repair. This modification deviated from the manufacturer's specifications. The extent to which this repair influenced the engine power loss could not be established because of the damage from the accident sequence.