NTSB Factual Report

The ski equipped airplane nosed over while landing on a frozen lake. The pilot reported that when he departed another seaplane base, the surface was very rough due frozen slush created by snow mobiles. He reported that when he touched down on the frozen lake, he heard a "loud grinding" noise and the airplane slowed down rapidly. The pilot stated the grinding noise stopped then started again only much louder. He reported the nose of the airplane dropped and the propeller contacted the ice. The pilot reported the airplane then dropped to the right and flipped over onto its back. The pilot reported the ground track from the left ski was "rounded" at initial touchdown followed by a space then a much narrower and deeper track. He reported the four quarter-inch bolts sheared off between the axle and the gear leg on the left ski.

NTSB Probable Cause

The pilot used a rough frozen lake for takeoff which resulted in the overload failure of the landing ski. A factor was the rough frozen lake.