Accident Description
The pilot reported that after making a low pass over the Medicine Lake area, he circled for a few minutes and then climbed to 7,500 ft. He established 2,000 RPM and 70 kts and continued the flight. Approximately five minutes later, he noticed that the trees appeared to be getting closer. He checked his vertical velocity indicator and observed a 200 ft/min descent. He then applied full throttle but did not notice an RPM increase and continued to lose altitude. Subsequently, the aircraft collided with a tree and crashed at an elevation of about 6,000 ft.
Engine Examination
During the investigation, the engine was examined and run on a portable test stand. It operated normally.
Environmental Conditions
The density altitude of the crash site was estimated to be 8,300 ft. The reported temperature and dew point in the area were 63°F and 32°F, respectively. According to icing probability charts, visible carburetor icing was possible at rated power. Additionally, updrafts and downdrafts were common in the area and were reported by other pilots.