Incident
During the initial climb at approximately 300 feet above ground level, the aircraft's upper cowl raised between 1 and 2 inches. The pilot reported that he remained in the traffic pattern. On base leg, the upper cowl dislodged further from the aircraft, creating drag. Unable to maintain altitude, the pilot performed a forced landing, during which the aircraft collided with power lines and homes located about half a mile from the runway.
Preflight Maintenance
Prior to the flight, the pilot, who owned the aircraft and worked as an Airframe and Powerplant (A&P) mechanic, had removed and partially replaced the engine cowl. A friend of the pilot, also holding an A&P certificate and a pilot, assisted by placing the left side of the upper cowl back onto the engine compartment. The surviving pilot reported that he had not observed the pilot-rated passenger physically secure the left side of the upper cowl to the engine compartment.
Wreckage Examination
During the examination of the wreckage, all of the fire-damaged cowl structure was found at the crash site except for the two forward-pointed upper cowl engagement pins and their supporting structure. Also missing was the nylon grommet or bushing that normally was seated in the lower cowl's left side forward plate assembly.