Accident Narrative
The accident involved a tail-wheel-equipped agricultural airplane. The pilot, a commercial pilot with 1,525 hours of flight time, had finished spraying a field and was departing the area. During a low altitude turn, the airplane experienced a partial loss of engine power and subsequently stalled, impacting a pond.
Witness Observations
A witness observed the engine "pop as it would if the mixture was too lean." The engine then sounded as if it "cleared up" and moments later the airplane turned back towards the witness's location. As the airplane proceeded, the engine was running but did not appear to be at "full throttle." When the airplane was approximately 150 feet above ground level (AGL), it made a 90-degree turn before it "plunged" nose-first into a pond.
Wreckage and Engine Examination
All major components of the airplane were accounted for at the site, and control continuity was established to the airplane's flight controls. An examination of the engine revealed that the crankshaft, connecting rods, and connecting rod bearings exhibited thermal and mechanical damage consistent with a lack of lubrication. The number four connecting rod bolt was found completely fractured. The oil sump, which had not been compromised during the accident, was found to contain residual oil. Investigators could not determine the reason for the loss of engine oil.