On September 13, 1989, an Air Tractor AT-301 (registration N8578S) was involved in an aviation accident near Mendota, CA. Investigators recorded the probable cause as: A LOSS OF AIRCRAFT CONTROL BY THE PILOT WHEN HE SLOWED THE AIRCRAFT TO BEGIN A SPRAY RUN. CONTRIBUTING TO THE LOSS OF CONTROL WAS THE INOPERATIVE STALL WARNING SYSTEM. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An aircraft settled downward while slowing for a spray run. The pilot added full throttle and jettisoned the hopper contents before impacting the ground. Investigators found the stall warning disconnected and the engine running on automotive fuel. No mechanical malfunctions were identified.
Accident Sequence
According to reports, the aircraft was decelerating to begin a spray run when it experienced a downward settling. The pilot responded by applying full engine power and releasing the hopper's contents. Despite these actions, the aircraft struck the ground.
Investigation Findings
Examination of the stall warning system revealed that it was not connected. The engine had been operated using automotive fuel. No mechanical malfunctions were discovered in the aircraft or engine prior to the accident sequence. The investigation did not find any pre-existing mechanical issues.
The exact circumstances leading to the descent were not detailed beyond the reported settlement. The stall warning system's disconnection and the use of automotive fuel were noted as findings.