Incident Overview
A witness observed an airplane during takeoff, reporting that the engine was running rough. Shortly thereafter, the airplane disappeared from view in a nose-down attitude. The pilot later stated that he could not recall the events leading up to the loss of power.
Post-Crash Examination
A thorough examination of the aircraft after the accident revealed numerous mechanical discrepancies. These included several spark plugs with cracked insulators, an inoperative magneto, contamination within the fuel system, and a blockage in the fuel tank vent system. Additionally, tool markings from a 'Vise-Grip' were found on several of the spark plugs, indicating possible improper installation or maintenance.
Engine Testing
When the inoperative magneto and defective spark plugs were replaced, the engine ran and developed satisfactory power on a test stand. However, when the original spark plugs were reinstalled, the engine would only develop partial power and could not exceed 1200 RPM.
Pilot and Maintenance Records
The pilot, who was also the owner of the aircraft, was unable to provide any maintenance records for the airplane. According to FAA records, the pilot's last medical examination had occurred 5 and a half years prior to the incident.