Flight Details
A pilot filed an IFR flight plan for a nonscheduled domestic cargo flight, carrying 270 pounds of freight. The flight was uneventful until established on the VOR/DME-C approach. Radar data showed the airplane turning inbound towards the VORTAC from the DME arc, then descending from 10,600 feet to the VOR crossing altitude of 9,200 feet. The track indicated slight left corrections as it proceeded inbound at 9,400 feet. Subsequently, the aircraft's track and altitude deviated significantly: 0.75 miles northwest at 9,700 feet, 0.5 miles southeast at 9,600 feet, and 0.5 miles northwest at 9,400 feet before disappearing from radar.
Weather Conditions
Witnesses reported 600-foot overcast skies, 1.5 miles visibility in misting rain that became "almost slushy on the ground," and a temperature of 36°F. A weather study indicated "an icing potential greater than 50% and visible moisture" in the accident area, and another report stated "icing conditions were likely present." The airplane was equipped and certified for flight into known icing conditions.
Pilot Information
The pilot was properly certificated but had only 38 hours of flight time in the aircraft make/model. He previously recorded 16 icing encounters totaling 11.2 hours in actual meteorological conditions, but no ice encounters and only 1.0 hour of simulated instrument time in the Cessna 208.
Aircraft Examination
The wreckage was found in a closely area (likely meaning a confined or wooded area). There was no evidence of pre-impact airframe, engine, or propeller malfunction or failure. Microscopic examination of annunciator light bulbs revealed the GENERATOR OFF light was illuminated, indicating a generator disconnection due to a line surge, tripped circuit breaker, or inadvertent switch operation. The operator's chief pilot noted that the Before Landing Checklist requires the IGNITION SWITCH be placed in the ON position. The START SWITCH is adjacent, and inadvertently moving it to ON would cause generator disconnection and illuminate the GENERATOR OFF light, which he said would be distracting to the pilot.
Probable Cause
The official probable cause was an inadvertent stall during an instrument approach, resulting in loss of control. Contributing factors were the pilot's attention being diverted by an abnormal indication, conditions conducive to airframe icing, and the pilot's lack of total experience in the type of operation (icing conditions) in the aircraft make/model.