On April 17, 1989, an Air Tractor AT-301 (registration N4340S) operated by Thomas Hill was involved in an aviation accident near Grangeville, ID. Investigators recorded the probable cause as: A suspected blower failure that resulted in a partial loss of power during the initial climb. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot experienced a partial power loss during initial climb, jettisoned the load, and landed in a soft field where the aircraft nosed over and caught fire before self-extinguishing.
What happened
During the initial climb phase of flight, the aircraft experienced a partial loss of power. In response to this emergency, the pilot decided to jettison the aircraft's load to reduce weight. The pilot then attempted an emergency landing in a soft field located approximately three-quarters of a mile from the runway. Upon impact with the ground, the aircraft nosed over. A fire subsequently erupted from the wreckage but self-extinguished several minutes later.
The investigation
The operator reported that a significant drop in manifold pressure had occurred prior to the emergency landing. Specifically, a 10 inch drop in manifold pressure was noted. This mechanical anomaly was identified as the primary indicator of the engine's performance degradation during the critical climb phase.
Probable cause
A suspected blower failure that resulted in a partial loss of power during the initial climb.