On June 6, 2000, a Gulfstream-schweizer G-164D (registration N8337K) was involved in an aviation accident near Welsh, LA. Investigators recorded the probable cause as: The excessive wear of the reduction gearbox's 1st stage sungear, which resulted in its subsequent fatigue fracture and failure. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An agricultural airplane experienced an engine failure during a return flight, forcing a landing in a flooded rice field where it nosed over. Post-accident examination revealed a fatigue failure in the reduction gearbox sungear.
Incident Overview
The pilot of an agricultural airplane was returning to the airport to pick up a second spray load when a deep humming sound was heard coming from the engine. White smoke was observed emanating from the engine's exhaust, and the propeller feathered and came to a stop. The pilot executed a forced landing in a flooded rice field. During the landing, the main landing gear dug into the mud, causing the airplane to nose over.
Engine Examination
A post-accident examination of the Pratt & Whitney PT6A-15AG engine was conducted. The examination revealed that one of the teeth on the reduction gearbox's 1st stage sungear had failed as a result of fatigue. The fatigue fracture originated from an area of pronounced wear. Additionally, numerous gear teeth displayed wear and spalling damage. Despite the wear, the gear was found to be within the manufacturer's hardness and dimensional limits. The engine had exceeded the manufacturer's recommended 3,500-hour overhaul period by 4,153 hours.