On November 1, 2013, about 0940 Pacific daylight time, a Mikoyan Gurevich Mig 21 UM, N20739, was substantially damaged during a runway overrun at the Reno-Stead Airport (RTS), Reno, Nevada. The airplane was registered to Migs of Delaware LLC., Wilmington, Delaware, and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The commercial pilot, sole occupant of the airplane, sustained serious injuries. Visual meteorological conditions prevailed and no flight plan was filed for the local personal flight that originated from RTS at 0915.In a written statement to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that following a normal landing on runway 14 (9,000-foot long and 150-foot wide asphalt runway), he initially applied braking. The pilot released the wheel brakes as the airplane decelerated to allow for cooling. As the airplane crossed the 4,000 foot remaining sign, he reapplied brakes with no braking action noted. He applied the emergency brake, however, did not immediately feel a response. The pilot shut down the engine and retracted the landing gear as the airplane approached the departure end of the runway. Subsequently, the airplane overran the departure end of the runway, traveled down an embankment, and came to rest upright. The pilot added that at the time the brakes failed, the airplane was too slow for an effective drag chute deployment. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the fuselage and wings were structurally damaged. The inspector stated that the emergency brake handle and drag chute both remained in the stowed positions. The airplane was recovered to a secure location for further examination. The inspector reported that the accident airplane brake system features control levers for the front seat (student or solo position) and rear seat (instructor position) that are stacked on a pivot point with only the rear seat brake levers physically actuating the pneumatic brake valve. The front seat lever engages the rear seat lever with a pawl. Spring tension holds the pawl in the engaged position, however, can be disengaged if the rear seat pilot elects to override the front seat pilot. The inspector reported that he coordinated with the pilot's mechanic to look at the airplane further; however, the mechanic disassembled the brake system prior to his arrival. The inspector stated that examination of the accident airplane revealed that a spring that holds the pawl in place and engaged was fractured and separated, which allowed the pawl to become disengaged. The disengaged pawl resulted in the deactivation of front brakes. Review of the Pilot's Flight Operating Instructions for the airplane stated, in part, "….if upon depressing the braking lever, the aircraft fails to get braked or one of the wheels gets sharply braked, proceed as follows: (a) release the braking lever, immediately deploy the drag chute and retract the flaps." The instructions further state "…after deployment of the drag chute, shut down the engine and use the emergency braking system."