Accident Sequence
The pilot reported departing with full fuel tanks (26 gallons total). Approximately 40 minutes into the flight, while cruising at 2,400 feet mean sea level, the engine rpm suddenly decreased from 2,400 to 1,500. The engine continued operating steadily at the reduced rpm. Application of carburetor heat and manipulation of throttle and mixture controls failed to restore power. The pilot contacted Macon Automated Flight Service Station (AFSS) to report the power loss and an impending off-field landing. He selected a service road among a large area of small pine trees for the landing. During the flare, the left wing tip contacted a 3-inch diameter tree trunk that was not visible during approach. The airplane then cartwheeled to the left, the nose landing gear separated after contacting soft ground, and the airplane nosed over. The pilot exited through the left door, which had popped open during the sequence. He reported no fuel leakage after exiting, and the airplane remained inverted for approximately 24 hours.
Communication Details
According to the Macon AFSS quality assurance manager, the pilot activated his VFR flight plan while airborne between 0830 and 0832. He contacted the facility again while airborne at 0910, advising of a fuel problem and losing altitude. A third contact was made via cellular phone at 0942. NTSB review of the in-flight communication tape confirmed the pilot stated he was having a fuel problem and losing altitude.
Post-Accident Examination
The FAA did not examine the airplane at the accident scene. Following recovery, an FAA inspector examined the airplane. Both fuel tank caps were found loose when installed, and the fuel vent diaphragm of the right wing fuel cap was torn. Aft streaking of fuel from both caps indicated poor seals. Only residual fuel remained in both fuel tanks; the exact quantity was not quantified. The gascolator bowl contained about 1/4 inch of fuel, while the carburetor bowl was empty.
Engine Testing
Before an attempted engine run, a differential compression test was performed. Cylinders 1, 3, and 4 measured at 76 or better against 80 psi, while the No. 2 cylinder measured 12 psi. The engine was run on the airframe with the accident propeller installed (straightened after impact). The engine started and operated to approximately 2,000 rpm with no discrepancies noted. Magnet checks at idle showed each dropped 75 rpm, and oil pressure was 45 psi during the run. Safety concerns prevented operation at higher rpm. Examination of photographs taken at the scene revealed the leading edges of both wings were at a lower elevation than the trailing edges.