What happened
A student pilot initiated flight operations but noticed a misfiring engine, described as a popping sound, while taxiing. She returned to the ramp and shut down the engine. Her husband agreed to accompany her on a test flight around the traffic pattern to check for malfunctions. They swapped seats, with the wife in the left seat and the husband in the right. After starting and taxiing again, no unusual sounds were detected, so they took off.
They departed the traffic pattern and climbed to 1500 feet. Upon encountering turbulence, the wife suggested returning to land. During the approach, the husband acted as pilot in command. He reported that when he retarded the throttle at approximately 75 feet above ground level, the engine did not respond. He attempted a go-around, but the engine only accelerated to about 2000 RPM, providing insufficient climb rate to clear obstructions.
Another attempt to retard the throttle failed. Subsequently, the aircraft collided with a building and some trees.
The investigation
Examination of the aircraft revealed no reason for a malfunction.