On May 24, 1997, an Ercoupe (eng & Research Corp.) 415-G (registration N94415) was involved in an aviation accident near Colusa, IL. Investigators recorded the probable cause as: improper installation of the rocker arm assembly by maintenance personnel which led to the failure of the rocker arm. A factor was the soft terrain. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During initial climb after touch-and-go landings, an aircraft experienced engine roughness and failure, leading to a forced landing in a field where it nosed over. Investigation found a broken and swapped rocker arm on cylinder two.
Accident Sequence
The pilot-in-command reported that during the initial climb following a series of touch-and-go landings, at an altitude of 250 feet, the engine began running rough and produced a clattering noise. The certified flight instructor (CFI) then took control of the aircraft. The engine subsequently quit completely, with the propeller stopping in the horizontal position. The CFI executed a forced landing in a freshly planted field. According to the CFI, the aircraft touched down firmly and rolled approximately 50 feet before the nose wheel dug in, causing the aircraft to go over onto its back, nose first.
Postcrash Investigation
Examination of the aircraft after the accident revealed that the exhaust valve rocker arm on the number two cylinder was broken in two pieces. Further inspection of the number two cylinder determined that the exhaust valve rocker arm had been interchanged with the intake valve rocker arm on the same cylinder.