Incident Overview
A Piper PA-28 aircraft, while on a 2-mile right base leg to land on Runway 24 at Hyannis Airport in Massachusetts, encountered a throttle malfunction after the pilot reduced power. The throttle became stuck in the closed position, preventing engine power restoration. Assessing that the aircraft could not reach the airport, the pilot opted to land on a highway.
Collision
As the aircraft was about to touch down on the highway, its landing gear struck a car traveling on the road. The impact resulted in the death of a passenger inside the car.
Post-Accident Examination
Examination of the engine revealed that the throttle shaft had seized with the throttle plate in the closed position. Further inspection of the shaft showed scratching and galling at the bushing. Subsequent testing of both the bushing and the shaft indicated that they were manufactured from the same material and exhibited hardness levels below the specifications set by the carburetor manufacturer. The carburetor had been manufactured approximately 10 flight hours before the accident.