What happened
A flight instructor provided instruction to a rated commercial pilot who had no prior experience flying this specific make and model of tailwheel airplane. During the flight, the pilot receiving instruction occupied the left seat, while the instructor was seated on the right side. Notably, the aircraft was not equipped with brakes on the right side where the instructor was positioned.
As power was applied for takeoff, the aircraft began to accelerate. The pilot in control failed to maintain directional control, causing the airplane to veer toward the left. Despite attempts by the flight instructor to correct the leftward movement using the rudder, the deviation could not be arrested. The aircraft subsequently departed the runway, became caught in a snow bank, and suffered a nose-over.