Incident Overview
A pilot reported that he took off to flight test an aircraft. After departure, he turned downwind to stay within the traffic pattern. On the downwind leg, the pilot reduced engine power to maintain spacing behind a Cessna 150. Once appropriate spacing was achieved, the engine power began to deteriorate.
Forced Landing
Due to the presence of other traffic, the pilot elected to make a forced landing in a field, short of the runway. During the landing roll, the right landing gear collapsed.
Possible Cause
The passenger and the aircraft owner suspected possible carburetor ice as a contributing factor, but this was not verified.
Conclusion
The event involved an unverified suspicion of carburetor ice, engine power loss, a precautionary landing off-airport, and a subsequent gear collapse.