Event Description
During flight, the aircraft's engine produced a hissing noise, as described by the pilot. An emergency was declared, and the pilot was vectored to the nearest airport. At an altitude of 5,000 feet while over the airport, the engine was shut down. During the subsequent forced landing, the airplane was flown beneath electrical transmission wires located near the runway threshold and impacted the ground approximately 200 yards short of the runway.
Examination Findings
Post-incident examination revealed that approximately half an inch of the Number 1 exhaust riser remained attached to the cylinder. The remainder of the riser was found in the lower section of the engine cowl. Soot deposits were observed on the engine cowl adjacent to the Number 1 exhaust riser. Additionally, a light brown discoloration was present on the Number 1 cylinder lower spark plug and on the fracture surfaces of the separated exhaust riser.
Manufacturer's Indication
Piper Aircraft Corporation indicated that misalignment of the cylinder head could result in a cracked stack assembly immediately below the stack assembly flange.