Cessna 402B N402BP accident near Aberdeen, South Dakota

Probable cause

The pilot's continued flight into adverse weather and icing conditions, and his failure to maintain aircraft control resulting in a hard landing. Contributing to the accident was the accumulation of airframe ice and the strong, gusting crosswinds.

NTSB analysis

The cargo flight encountered moderate icing conditions during the initial climb to the planned cruise altitude. The deice boots, pitot tube heat, stall vane heat, propeller deice, and windshield hot plate were used throughout the flight. The flight was subsequently cleared to a higher altitude, where it remained above the cloud tops and did not accrue any additional ice. The unprotected areas of the wings and windshield were still contaminated with ice when the pilot began his initial descent into the destination airport. The unprotected areas of the airplane continued to accrue ice while being vectored to join the instrument approach to runway 31. The pilot reported having difficulty aligning the airplane with the runway because the windshield was obscured by ice, except for a narrow section protected by the hot plate. The airplane crossed over the runway threshold at 120 knots indicated airspeed. The pilot stated that immediately prior to touchdown he had the sensation of a high sink rate, which was followed by the hard landing. After the flight, there was 1 to 1-1/2 inches of ice accumulation on the unprotected areas of the airplane. The protected areas of the wing, tail, windshield, and propeller blades were free of any appreciable ice contamination. The right wing primary structure, including the main wing spar and engine nacelle assembly, was substantially damaged during the hard landing. The local winds were 360 degrees true at 22 knots, gusting to 30 knots. During the accident flight, there was an active advisory for moderate icing conditions below 15,000 feet mean sea level and a freezing level at the surface.

Text from the NTSB. Open the NTSB docket for CEN09LA206 for the full record.