Departure with Ice Contamination
The pilot of a Cessna 208B initiated a flight while the airplane was contaminated with ice, proceeding directly into known severe icing conditions. Unable to maintain altitude, the aircraft subsequently struck trees and terrain.
Witness Accounts of Pre-Flight Ice
Multiple witnesses at the departure airport reported that the accident airplane arrived already contaminated with ice. Several witnesses recalled asking the pilot whether he required de-icing service before his next departure, to which he declined. Additionally, witnesses observed the pilot manually chipping pieces of ice off the airplane prior to departure.
In-Flight Icing Encounter
During the flight, the pilot communicated that the airplane had encountered icing conditions and that he was unable to maintain altitude. After the accident, several thick ice fragments were recovered near the site. One recovered piece exhibited a semicircular edge consistent with the leading edge of an airfoil.
Examination of De-Ice Systems
Post-accident examination revealed no pre-impact anomalies with the leading edge de-ice boots, which were installed on both wings, the vertical and horizontal stabilizers, and the wing struts.
Regulatory and Operational Guidance
Federal Aviation Regulations stipulate that all ice contamination must be removed prior to flight. The Cessna 208B Pilot Operating Handbook explicitly states that continued flight into known icing conditions must be avoided.
Official Probable Cause
The probable cause determined by investigators was the pilot's failure to remove ice contamination from the airplane prior to departure and his intentional flight into known severe icing conditions, which resulted in the aircraft's inability to maintain sufficient altitude to clear the terrain. Contributing factors included the prevailing icing conditions and the trees encountered during the forced landing.