On July 7, 1999, a Grumman-schweizer G-164A (registration N7869) was involved in an aviation accident near New Plymouth, ID. Investigators recorded the probable cause as: Loss of engine power due to failure of the supercharger impeller. A contributing factor was the ditch. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
After takeoff, the pilot experienced a loss of engine performance and attempted to return to the airstrip. Unable to maintain altitude, the chemical load was dumped. A forced landing was made in a sugar beet field, but the aircraft could not stop before hitting an irrigation ditch and impacting upsloping terrain. Inspection found a broken supercharger gear tooth.
Incident Summary
Shortly after takeoff, the pilot detected a reduction in engine performance. In response, the pilot attempted to return to the departure airstrip. However, the aircraft could not maintain altitude, prompting the pilot to jettison the chemical load. The pilot then initiated a forced landing in an agricultural field planted with sugar beets.
Emergency Actions and Landing
During the forced landing, the aircraft was unable to stop before reaching an irrigation ditch. It subsequently impacted the upsloping terrain on the opposite side of the ditch. The sequence resulted in the aircraft coming to rest in the field.
Engine Inspection
A partial disassembly of the engine was conducted. Inspection revealed that a gear tooth from the engine's supercharger blower section had broken off. The detached tooth was found within the blower drive section of the engine.