Accident Description
A witness reported observing the accident airplane flying level above the trees when it abruptly started a steep, nearly vertical climb. At the apex of the climb, the airplane descended in a steep spiral and impacted the ground. The impact occurred in a near-vertical, nose-low attitude.
Aircraft Damage
The right wing was found standing on its leading edge, with its top wrapped counter-clockwise around a small group of willows. The two-bladed propeller exhibited extreme bending and torsional twisting, chord-wise scratching, and areas where paint had been sanded clean. The engine exhaust manifold showed plastic folding.
Pilot Information
The pilot was the owner of the airplane and held a certified aircraft mechanic rating. According to reports, the pilot maintained the accident airplane. No airframe or engine logbooks were discovered for examination.
Investigation Findings
No preimpact mechanical problems were discovered during the investigation. Federal Aviation Regulation Part 91.303 defines any abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration not necessary for normal flight as aerobatic flight.