What happened
During an active fire suppression operation, an air tanker was engaged in dropping fire retardant chemicals. The aircraft had successfully completed two prior drops on the fire line before the incident occurred. While transitioning from the base leg to a westerly heading to align with the downwind drop, the aircraft was executing a 6-0 degree left bank.
Witnessed by both a spotter pilot and another tanker crew, the aircraft experienced a sudden roll to the left, increasing the bank angle to 90 degrees. During this maneuver, the left wingtip made contact with the ground.
Findings
Environmental conditions at the time of the accident were significant. Pilots on the scene reported experiencing turbulence and unstable air. Wind speeds were estimated between 25 and 30 mph, with gusts exceeding 40 mph originating from the east. Additionally, an Airmet Tango had been issued for the area, warning of turbulence and isolated severe weather conditions, particularly at altitudes below 10,000 feet near canyons and mountain passes. The sudden roll to a 90-degree bank led to the wingtip striking the terrain.