Overview
While cruising at 17,000 feet in instrument meteorological conditions (IMC), an aircraft encountered deteriorating weather. Other nearby aircraft reported moderate turbulence and icing conditions within layered clouds. The pilot informed air traffic control that the autopilot had been lost, and the aircraft's course began changing radically. A ground-based witness described the approaching aircraft's noise as similar to the 'screaming' produced by an aircraft in a power dive. Surface visibility was restricted by snow to between 200 feet and one-quarter mile.
Sequence of Events
After the pilot reported the autopilot loss, the aircraft's trajectory deviated significantly. Control of the aircraft was subsequently lost, leading to an inflight breakup. The wreckage was found distributed over an area measuring one-eighth by three-quarters of a mile.
Wreckage and Failure Analysis
Examination of the wreckage revealed that the primary airframe failure occurred on the left side of the wing spar carry-through structure. The structure broke in an upward (positive) direction. Investigators found no evidence to support the reported loss of the autopilot or any related flight control system malfunction.
Findings
The aircraft was neither certificated nor equipped for flight into icing conditions.