Overview
While in radio and radar contact with FAA Greenville/Spartanburg's Departure Control, the pilot reported a very rough running engine as the aircraft climbed through 7,900 feet msl toward an assigned altitude of 9,500 feet msl. The aircraft was approximately 30 miles northwest of the Greenville/Spartanburg Airport at the time. The controller provided vectors that brought the airplane to within 7 miles of the nearest airport, at which point the pilot opted to conduct a forced landing in a farmer's field rather than continue to the airport.
Sequence of Events
During the forced landing attempt, the airplane collided with two pine trees within a stand of pines, striking them about 40 feet above ground. The impact occurred with the aircraft in a relatively flat, wings-level, upright attitude. After the initial collision, the airplane continued airborne for approximately 310 feet over a relatively clear field before impacting dense brush and small trees ranging from 8 to 12 feet in height. The final impact occurred in an inverted attitude.
Investigation Findings
Subsequent disassembly and examination of the engine and its associated components revealed no mechanical cause for the roughness reported by the pilot. The toxicological evaluation of the pilot's blood and urine reported a finding of 0.056 ug/ml (ug/g) of Diphenhydramine, an antihistamine.
The investigation did not determine a reason for the engine roughness, and no probable cause for the event was stated.