Narrative
During a circling flight in a southbound direction, the engine exhibited repeated power fluctuations: running for about 4 to 5 seconds, then quitting for 2 to 4 seconds, with the cycle recurring. At that time, an approximate 600-acre sod farm was located 1.29 nautical miles west of the airplane's position. The airplane was observed continuing southbound while circling, then flying low over trees and circling twice over a field sparsely occupied by trees. Subsequently, the airplane rolled inverted and impacted the ground in a slightly inverted attitude.
Examination Findings
Examination of the flight controls revealed no evidence of preimpact failure or malfunction. Examination of the engine disclosed that the mixture control cable was separated from the control arm at the servo fuel injector. A non-aviation washer had been used in the mixture control cable installation and was found failed; the cable attach hardware was in place. No engine mechanical failure or malfunction was noted. Bench testing of the impact-damaged servo fuel injector showed that the fuel flow momentarily remained high when the throttle was reduced. Disassembly of the servo revealed that the fuel diaphragm stem was bent. The fuel servo was last overhauled in 1991, and the fuel diaphragm was reportedly replaced at that time, but the part number of the installed unit at the time of the accident was not the same as the diaphragm after replacement.