What happened
While operating under visual flight rules to deliver mail to a remote location, the pilot monitored the automated weather observing system (AWOS) for updates. Although the pilot believed visibility was approximately 7 miles, the actual AWOS report 18 minutes prior to the accident indicated visibility was no more and no less than 1.75 miles. As the aircraft descended from 2,500 feet to 1,500 feet within the terminal area, the pilot encountered the reduced visibility, necessitating an instrument approach.
During maneuvers toward the initial approach fix, the autopilot disconnected, causing the aircraft to enter an uncommanded descent. The pilot attempted to use the control wheel to level the aircraft, but the plane struck the ground. The impact caused substantial damage to the rudder, vertical stabilizer, and fuselage. Data analysis showed the aircraft was in a continuous descent from 2,500 feet until it was only 12 feet above the ground, never reaching a level flight state. In the final 15 seconds, the descent rate accelerated from 500 fpm to 2,300 fpm.
Findings
Post-accident inspections of the engine, airframe, flight controls, and autopilot systems found no mechanical failures or malfunctions that would have prevented normal operation. The investigation suggests that the need to transition to an unplanned instrument approach increased the pilot's workload. The pilot failed to arrest the descent rate after the autopilot disconnected, likely because the low visibility prevented him from noticing the aircraft's downward trajectory.