Accident Sequence
The airplane was observed in level flight with the engine sputtering and cutting out. Witnesses reported that the left wing dropped, followed by the right wing, and the airplane entered a spin to the left. As the airplane rotated toward the ground, witnesses described the engine running at full power.
Fuel System Examination
Fibrous foreign material was found on all fuel system screens. Bench testing of fuel system components, including the metering unit screen during an exemplar engine run, showed all results within manufacturer specifications. Fuel samples taken from refueling locations met standard specifications for aviation gasoline 100LL. The fibrous material from the fuel metering screen and bladder fuel cells consisted of various types of fibers, but a definitive source could not be determined.
Weight and Balance
The airplane's maximum gross weight was 3,600 lbs, with a center of gravity (CG) range of 82.1 to 83.8 inches. At the time of the accident, the calculated weight was 3,466.5 lbs with a CG of 87.00 inches, which is aft of the allowable range.
No other contributing factors were identified in the investigation.