On July 31, 2011, about 1545 eastern daylight time, a Nord Stampe SV4C, N51SV, was substantially damaged following a loss of engine power and collision with terrain at Old Rhinebeck Airport (NY94), Rhinebeck, New York. The commercial pilot sustained minor injuries. The airplane was registered to and operated by the Rhinebeck Aerodrome Museum under the provisions of 14 Code of Federal Regulations Part 91 as an air show flight. Visual meteorological conditions prevailed and no flight plan was filed. The local flight originated at NY94 about 1500. The pilot reported the following. He was participating in an air show demonstration, called a "bombing routine." Fuel was added to the fuel tank prior to engine start, and the flight departed with about 12 gallons on board. Aircraft preflight and ground operations were normal. During one of the bombing runs, about 350 feet above the ground, he dropped his bomb and added throttle to pull up and away for the next pass. He heard a "pop" and the engine rpm decreased. He unsuccessfully attempted to recover the engine with throttle movements. He attempted a restart, confirmed the fuel valve positions, and checked the magnetos. Unable to restart the engine, he attempted a forced landing. The airplane clipped trees and came to rest, inverted, at the edge of a stand of trees at the south end of the runway. An inspector with the Federal Aviation Administration responded to the accident site and examined the wreckage. There were approximately five gallons of fuel remaining in the fuel tank. Both upper and lower wings received structural damage. An examination of the engine revealed normal spark plug color and wear and the exhaust was clean. Internal engine continuity was confirmed. The wreckage was recovered to the museum hangar where a detailed examination of the fuel system was performed. After recovery of the wreckage, the engine-driven fuel pump was removed from the engine and examined. The pump was disassembled and found in an "operational condition internally." No reason for the loss of engine power was found.