Flight Details
The pilot and passenger departed Bozeman Yellowstone International Airport at 1500 Mountain Daylight Time and flew to Hughes Bay on Flathead Lake, near Lakeside, Montana, arriving at approximately 1700.
Landing and Incident
During the approach, the pilot observed a diminishing wave pattern from the southwest and a strong gust surface pattern from the east. There were no whitecaps, but the water was rougher toward the middle of the lake. The pilot estimated the winds were from the east at 5 knots. After dragging the intended landing area, the pilot determined it was safe to land and performed a step landing.
During the landing, the aircraft grazed the first wave at 65 miles per hour, bounced off the second wave, and settled on the third wave. The aircraft then spun 90 degrees to the right.
Aftermath
After the incident, the pilot discovered that the left float had collapsed, the right float was crushed, and there was other substantial damage to the aft fuselage. The pilot suspected that the aircraft struck floating debris in the lake. The pilot operating handbook recommends a full stall landing in high wind and wave conditions.
Probable Cause
No probable cause was stated in the source.