On August 28, 1995, about 0800 eastern daylight time, a Markwood, BD-4, experimental, homebuilt airplane, N511BD, collided with the terrain during the landing roll at the Connellsville Airport, Connellsville, Pennsylvania. The airplane was substantially damaged. The private pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed. The personal flight was being conducted under 14 CFR Part 91. The airplane had landed on Runway 23 (3,457 feet long and 100 feet wide). The pilot stated that when he applied the brakes after touchdown: ...the right brake completely failed immediately; the left brake functioned and pulled the aircraft to the left. Right rudder correction was unable to correct this and the aircraft went off the left end of the runway [into a ditch]. The FAA examined the brakes and found, "no signs of visible fluid leakage or broken lines...." The FAA Inspector further stated: ...after removing the brake master cylinder caps to check for fluid, the right hand cylinder showed no signs of fluid and the left hand showed very little signs of fluid. I functionally checked the brake pedals finding the left spongy and the right hand hit the mechanical stop. At the time of the accident, the pilot had 590 total flight hours, and 380 flight hours in this make and model airplane. The reported local weather was; clear, visibility 12 miles, temperature 73 degrees F, winds calm, altimeter 30.05 inches Hg.