Accident Sequence
A flight instructor and a certificated pilot were conducting a local instructional flight. According to a witness, the aircraft powered up and began its takeoff roll. The witness then heard the engine "skip," prompting him to look up and see the airplane in a steep left turn with a nose-high attitude. Simultaneously, the engine noise decreased, as if the throttle was pulled to idle. When the airplane was approximately parallel with the "old runway 28," the witness observed the tail swing aggressively to the right, and at the same time, he heard the engine rev up. The airplane then stalled and began to spiral downward counter-clockwise before impacting the asphalt and bursting into flames. Several other witnesses reported seeing the airplane flying 30 minutes prior to the accident.
Examination Findings
Inspection of the carburetor revealed contaminated residual fuel and contamination of the fuel screen. Examination of the fuel sample and fuel screen showed that the fuel contained water, copper sediments, and varnish, consistent with "old fuel." Residue on the fuel screen was consistent with grease.
Maintenance History
The local training flight was the airplane's first flight since the annual inspection performed 2 months prior to the accident. Review of maintenance records indicated that the most recent annual inspection was completed on April 1, 2003. The work accomplished included draining the fuel sumps and inspecting the fuel screen. Additionally, the records contained a checklist for a 100-hour inspection dated March 31, 2003, and a discrepancy sheet log. The checklist included items such as "Drain carburetor float bowl - resafety plug... Remove fuel inlet screen from carb or injection throttle body, clean, reinstall and safety." These items were initialed by a mechanic and additionally by an inspector. The discrepancy sheet log contained an entry stating, "carb float bowl drain froze in place, fab tool to remove and removed drain plug," initialed by a mechanic. According to 14 CFR Part 43 Appendix D, annual and 100-hour inspections require inspection of applicable engine and nacelle group components.