What happened
The aircraft took off toward the south, climbing to an altitude of approximately 50 to 100 feet, just above the tree line. As the pilot began a right-hand circling turn, the aircraft completed a full 360-degree rotation. While the aircraft was at a 10 to 15-degree nose-high attitude, the nose dropped, resulting in a descent at a 60-degree nose-down attitude.
The investigation
Mechanical examination of the engine showed no deficiencies. However, inspection of the propeller revealed significant damage: one blade was broken aft in the direction opposite to rotation, and another blade was broken straight back toward the engine.
Investigators also analyzed a fuel sample drained from the aircraft's fuel strainer bowl. The fuel was green, cloudy, and described as resembling "muddy water," and it contained unidentified debris. Records indicated the aircraft was last fueled with 9 gallons of 100LL aviation gasoline on October 17, 1999, and there was no record of flight activity since that date.