Background
The pilot was being vectored by air traffic control to avoid thunderstorms in the vicinity. During the last radio contact, the controller issued a vector toward the destination airport. The pilot did not mention any problems during that transmission.
Accident Sequence
While executing the turn, the aircraft lost control for reasons that were not determined. It descended from its assigned altitude of 6,000 feet mean sea level (msl) to the ground in approximately 40 seconds. At the time, the aircraft was reportedly in clear weather conditions and had not encountered adverse weather during the entire flight. Impact occurred in a shallow lake while the aircraft was in a near-vertical nose-down attitude at a high rate of speed. Both occupants were killed.
Investigation
Investigators found that the right propeller was feathered at impact, while the left propeller was in the cruise range. Post-accident tests revealed no evidence of any preimpact failure or malfunction of the right engine or propeller. Pathological and toxicological examinations showed no physiological factors that would have impaired the pilot. The pilot's flight time records were not available at the time of the investigation.
Probable Cause and Findings
The official probable cause was listed as undetermined. The investigation identified that the pilot had feathered the propeller and had not maintained airspeed. The reason for the loss of control could not be established.