Aerospatiale AS350 N346AE accident near Ponca City, Oklahoma

Probable cause

The pilot's failure to maintain altitude during the hover operation while his view was obstructed due to the fogged-over windshield.

NTSB analysis

The pilot and an air ambulance crewmember were repositioning the helicopter due to incoming inclement weather. About halfway into the flight, the front windshields were fogging over, and the pilot increased the demister. Upon reaching the destination, the pilot hovered near the company hangar; by this time, the windshields had completely fogged over. The crewmember warned the pilot that he was getting close to the hangar, which was on the helicopter's left side. The pilot felt that he was high enough off the ground to move the helicopter several feet to the right, but the right skid was too low and contacted the ground, which resulted in a dynamic rollover. The helicopter sustained substantial damage to the rotor blades, fuselage, and tailboom.

Based on the available information, the dynamic rollover was a result of the pilot's failure to maintain altitude during the hover operation with a fogged-over windshield.

Text from the NTSB. Open the NTSB docket for CEN19LA068 for the full record.