On May 25, 1990, a Grumman 164-B (registration N9982) operated by Thompson Dusting Service was involved in an aviation accident near Garwood, TX. Investigators recorded the probable cause as: Failure of the supercharger impeller shaft bearings, which caused failure of the supercharger impeller; failed parts contaminated the air intake system, causing the intake and exhaust valves to be wedged open. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot experienced a partial power loss while spraying a field. Unable to maintain flight, he performed a forced landing in a wet, soft adjacent rice field, resulting in a noseover. Engine examination revealed supercharger impeller shaft bearing failure.
Accident Narrative
While conducting an aerial spraying operation, the pilot encountered a partial power loss over the field he was treating. He was unable to sustain flight and executed a forced landing in a wet, soft rice field adjacent to the intended area. During the landing, the aircraft nosed over.
Engine Examination Findings
A subsequent examination of the engine identified the root cause of the power loss. The supercharger impeller shaft bearings had failed, leading to the failure of the supercharger impeller itself. Debris from the failed components contaminated the air intake system. This contamination caused both the intake and exhaust valves to become wedged in the open position, which resulted in the loss of engine power.
Probable cause
Failure of the supercharger impeller shaft bearings, which caused failure of the supercharger impeller; failed parts contaminated the air intake system, causing the intake and exhaust valves to be wedged open.