Accident Sequence
About 14 minutes after departure on a cross-country flight in instrument meteorological conditions (IMC), the airplane was observed on radar climbing through 14,800 feet mean sea level (msl). At that point, the pilot radioed air traffic control (ATC) that he was returning to the departure airport. Approximately 7 seconds later, the pilot transmitted that he had lost an engine and again stated he was returning. About 50 seconds after that, the pilot transmitted, "We're losing it," after which no further communication was received.
Radar data showed that at 14,800 feet msl, the airplane began a right 360-degree turn at a rate of 8 degrees per second. About 120 degrees into the turn, it began a descent averaging 5,783 feet per minute. The airplane continued in a right turn until radar contact was lost at 10,700 feet msl.
Impact and Witness Report
The airplane impacted a densely forested mountain on a 30-degree slope at an elevation of about 2,940 feet msl. The impact attitude was near vertical, with a slight right-wing-low orientation. A logger working nearby reported hearing a "very loud roaring sound," like an airplane diving toward his location, and that it seemed to be "really under power." The logger described the weather as "socked in," with light rain and not much wind.
Postaccident Examination
Postaccident examination revealed that propeller damage was consistent with impact forces; there were no indications of fatigue or propeller failure before impact. It was noted that the left propeller was operating under some power at impact, while the right propeller was not operating under significant power at impact. Examination of the airframe and both engines did not reveal any mechanical malfunctions or failures that would have precluded normal operation. The reason for the partial loss of engine power could not be determined.
Probable Cause
The probable cause was determined to be the pilot's failure to arrest the excessive rate of turn into the failed engine, which resulted in a loss of control and subsequent impact with terrain. Contributing to the accident was a partial loss of engine power for reasons that could not be determined because postaccident examination did not reveal any mechanical malfunctions or failures that would have precluded normal operation.