On June 30, 1991, a Cessna 140 (registration N89209) operated by Edward J. Foody was involved in an aviation accident near Lancaster, NY. Investigators recorded the probable cause as: Progressive fatigue failure of the number 3 exhaust valve. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A Piper Cherokee (N89209) made a forced landing in a field after the pilot heard a pop and rattling from the engine. The landing struck a ditch. Examination revealed a broken number 3 exhaust valve due to progressive fatigue.
Incident Overview
A Piper Cherokee, registration N89209, was in cruise flight when the pilot heard a pop followed by a rattling sound emanating from the engine. The pilot reported that he attempted to reach an airport and increased throttle, but the engine vibrated and knocked excessively. He subsequently performed a forced landing in a field. During the landing roll, the airplane struck a ditch, causing damage to the aircraft.
Post-Incident Examination
After the incident, an examination of the engine was conducted. The examination revealed that the number 3 exhaust valve had fractured. Further metallurgical analysis of the valve determined that the fracture was the result of progressive fatigue, as opposed to an instantaneous overload failure. This fatigue over time led to the valve's weakening and eventual breakage, which in turn caused the engine malfunction.
Key Facts
The pilot heard a pop and rattling from the engine during cruise.
The pilot attempted to reach an airport but aborted due to severe vibration and knocking.
The forced landing was made in a field; the airplane struck a ditch during the landing.
Examination found a broken number 3 exhaust valve.
Metallurgical examination confirmed the valve failed due to progressive fatigue, not overload.
Probable cause
Progressive fatigue failure of the number 3 exhaust valve.