On October 29, 1989, a Grumman AA-1A (registration N9330L) operated by John L. Lee was involved in an aviation accident near Borrego Springs, CA. Investigators recorded the probable cause as: THE FAILURE OF THE ENGINE EXHAUST VALVE. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A 23-year-old private pilot experienced a complete loss of engine power during cruise flight. An emergency landing in the desert ended with the aircraft colliding with a berm and nosing over. Examination found a separated exhaust valve and necked stems on other valves.
Accident Overview
A 23-year-old private pilot, recently certified, was flying an 18-year-old flying club airplane when the engine lost all power during cruise flight. The pilot executed an emergency landing in the desert, but the aircraft struck a berm and nosed over.
Aircraft Information
The airplane and its engine had accumulated a total of 2,093 hours of operation. No record was found of the engine having been overhauled. The aircraft had been inactive for two periods totaling eight years over its lifetime.
Engine Examination
Post-accident examination of the engine revealed that the No. 1 exhaust valve head had separated from its stem, which was necked down at the point of failure. The three other exhaust valve stems were also found to be necked down in the same general area. The engine had a recommended time between overhaul (TBO) of 2,400 hours if kept in continuous service.