Accident Overview
Witnesses observed an airplane on base turn for runway 34, making a normal-sounding call on the common traffic advisory frequency (CTAF). Shortly after, the aircraft's nose dropped and it crashed into a cattle pasture approximately three-quarters of a mile from the runway threshold.
On-Site Examination
Examination of the wreckage and impact signatures indicated an uncontrolled impact with a right wing low attitude and relatively low speed. Physical evidence and instrument readings suggested a power loss from the left engine. The left propeller was not feathered at impact, and both landing gear and flaps were fully extended.
Left Engine Power Loss
The reason for the left engine power loss could not be determined. However, investigators noted several observations potentially related to left engine performance:
- Both engines had accumulated approximately 300 hours beyond the manufacturer's recommended time between overhauls (TBO).
- Post-accident testing of fuel system components revealed evidence of improper idle mixture and idle stop adjustments performed by maintenance personnel. A work order dated the day before the accident, but not reflected in aircraft or engine logbook entries, indicated adjustments to "MIXTURE IDLE CUTOFF" and "FUEL PRESSURE" on both engines.
- The left side fuel selector was found in the AUX position. The aircraft owner's handbook specifies the MAIN position for descent and landing.
Propeller Feathering Tests
Post-accident testing demonstrated that the left propeller feathered quickly and smoothly when oil pressure was removed from the hub, and that the left propeller governor would cut oil pressure to the hub as designed.