Summary
Witnesses reported that the airplane did not appear to be climbing normally after takeoff. The pilot recalled turning back towards the runway. The pilot-rated passenger stated there had been a power loss 'as if the power had been brought back to idle.' Subsequently, the left wing dropped, and the airplane collided with terrain.
Narrative
After departure, witnesses observed the airplane struggling to gain altitude. The pilot maneuvered back toward the runway. The pilot-rated passenger described a sudden reduction in engine power resembling a throttle retarded to idle. The airplane then entered a left-wing-low attitude and struck the ground.
Investigation Findings
The mixture control was found in the full rich position. A 4-inch by 3/8-inch piece of baffle seal material was discovered next to the venturi in the air intake side of the carburetor throat, lodged between the accelerator pump discharge tube and the power jet. The undisturbed carburetor was factory tested on a similar engine, which operated 'extremely rich.' One pilot who had previously flown the airplane stated that the engine did not develop full power. Another pilot-instructor noted that the engine required 'more leaning' than other Cessna 172s he had flown. The airport elevation was 6172 feet.
Probable Cause
The investigation did not specify a probable cause.