The pilot of the tailwheel-equipped airplane was performing touch-and-go landings. During the third landing, the pilot noticed that right wheel began to “drag.” During the next landing, the airplane veered to the right side of the runway. The tail of the airplane then lifted and the airplane nosed over. The fuselage, wings, and vertical stabilizer were substantially damaged. After exiting the airplane, the pilot attempted to rotate the right wheel assembly, and it would not rotate. After about an hour the wheel assembly freed up and was able to rotate. A postaccident examination of the brake system revealed that the brake master cylinder lock seal spring had broken into three pieces. Given this information, it is likely that the broken lock seal spring washer prevented the master cylinder from releasing pressure from the caliper. This malfunction resulted in the right brake caliper staying engaged after the pilot released the brakes.