Accident
During initial climb after takeoff, the pilot experienced a gradual loss of power. The aircraft executed a forced landing approximately three-quarters of a mile northwest of the airport. During the landing, the airplane collided with a soccer field goal post and subsequently crashed to the ground.
Investigation
Post-accident examination included a test run of the engine, which operated to the manufacturer's specifications. No anomalies were found in the exhaust or fuel distribution systems. Further inspection of the engine induction system revealed an object lodged adjacent to the alternate air adapter assembly. The object was identified as an alternate air door, part number 23809-07, which was designed for an earlier model PA-28R aircraft and should not have been installed on the accident aircraft.
Evidence showed that the air box cover on the accident aircraft had been replaced in 1986 with a part number 67745-00 door, the correct part for the aircraft. However, there was evidence that the incorrect alternate air door had been previously installed at some point. That incorrect door had broken off and been ingested downstream into the induction system. It is likely that when the mechanic replaced the air box cover, the broken door was overlooked or not visible, leaving it within the system.
Findings
The investigation determined that the engine power loss was consistent with a restriction in the induction system caused by the presence of the incorrect alternate air door. The door's presence obstructed airflow but was not discovered during the post-accident engine test run, which was conducted without the induction system assembled. The origin of the incorrect door remains unknown, but it was not part of the intended configuration for the aircraft.