On July 23, 2004, a Grumman G-164A (registration N7220) operated by Donald L. Taylor was involved in an aviation accident near Nyssa, OR. Investigators recorded the probable cause as: The number four cylinder head fractured near where the cylinder head was screwed into the cylinder barrel, and the fracture was of such a nature that it kept the cylinder from developing the compression necessary for detonation of the fuel/air mixture. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During an aerial application flight, a loud bang preceded engine power loss, forcing a landing in a field where the main gear collapsed in soft terrain, resulting in a nose-over. Investigation found a fractured number four cylinder head.
Incident Overview
An aerial application aircraft experienced a sudden loss of engine power during a spraying run. The pilot reported hearing a loud bang, after which the engine significantly reduced power output. Unable to maintain altitude, the pilot initiated a forced landing in a nearby agricultural field.
Landing and Subsequent Events
The initial touchdown was uneventful; however, the main landing gear contacted soft terrain and dug in. The gear subsequently collapsed, causing the aircraft to nose over.
Investigation Findings
Following the incident, examination determined that the number four cylinder head had fractured in flight. The fracture occurred near the point where the cylinder head is screwed into the cylinder barrel. The nature of the fracture prevented the cylinder from achieving the compression necessary for detonation of the fuel/air mixture, leading to the power loss.
Probable cause
The number four cylinder head fractured near where the cylinder head was screwed into the cylinder barrel, and the fracture was of such a nature that it kept the cylinder from developing the compression necessary for detonation of the fuel/air mixture.