Cessna U206G N4891Z accident near Skwentna, Alaska

Probable cause

The airplane’s float contacted an undetected submerged gravel bar during landing which resulted in a nose over.

NTSB analysis

While landing on a river and coming off the float step, the airplane’s float contacted an undetected submerged gravel bar in shallow water. The airplane pivoted, nosed over, and came to rest inverted. The airplane sustained substantial damage to the vertical stabilizer and rudder. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.

Text from the NTSB. Open the NTSB docket for ANC23LA063 for the full record.