Skydiving Aircraft Forced Landing After Engine Failure Due to Piston Defects (N5010D)

Incident Overview

Passengers (parachutists) reported hearing backfiring, a bang, and seeing white smoke after the airplane became airborne. The jumpmaster reported that the engine quit after the airplane turned downwind. The airplane continued to lose altitude on downwind and during the turn to the runway. It crossed the approach end of the runway at a 45-degree angle and dragged a wing on the runway, coming to rest next to the runway.

Engine Examination

Examination of the engine disclosed that the skirt on the #3 piston (Superior Air Parts P/N 626992) had failed up to the lower ring groove. The remaining pistons had cracks which were oriented on the longitudinal axis of the piston, 90 degrees to the wrist pin. Metallurgical examination of the pistons showed sharp corners on the inside of the skirt, and surface shrinkage cavities in the sharp corners of the mold which were the source of the fatigue cracks observed in the remaining pistons.

Weight Condition

The airplane was at least 40 lbs over its maximum allowable takeoff weight.