Flight Sequence
During the downwind leg of the traffic pattern, the pilot set the mixture to 50 degrees rich of peak, positioned the propeller lever full forward, and reduced the throttle to 1,200 RPM. After turning base, the pilot reduced the throttle in preparation for extending the flaps. When the pilot increased the throttle to maintain altitude, the engine power did not increase as expected.
Engine Response
The pilot checked the fuel pump, which was on, and applied carburetor heat. This action, according to the pilot, "produced a constant and noticeable further loss of power." The cockpit gauges indicated all parameters in the green, and the propeller was verified to be in the full forward position. The manifold pressure was approximately 12 inches, and the engine tachometer indicated 2,000 RPM.
Forced Landing
The pilot turned the airplane toward the runway but could not reach it. A forced landing was attempted onto a nearby road. During the landing, the airplane touched down in a ditch approximately 20 feet from the road. The right wing struck a fence post, and the airplane came to rest upright.
Post-Accident Examination
At a salvage facility, the engine was examined and test-run twice at various power settings. No anomalies were noted during the examination or test runs. A review of a carburetor icing probability chart placed the reported temperature and dew point in the "icing at glide and cruise power" area of the chart.