On August 27, 2002, at 0940 mountain daylight time, a Whittman Tailwind W-8 homebuilt single-engine airplane, N3992A, was substantially damaged during a forced landing following the separation of a propeller blade while maneuvering near Albuquerque, New Mexico. The airplane was owned and operated by a private individual. The instrument rated private pilot and his passenger were not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 maintenance test flight. The local flight originated from the Double Eagle II Airport, near Albuquerque, at 0920. The pilot reported to the FAA that the flight was being conducted to evaluate a recently installed ground adjustable propeller. After departing from runway 22, the flight climbed to 7,500 feet while evaluating the climb performance of the newly installed propeller. After maneuvering for a short time, the pilot and his passenger decided to return to the airport to readjust the propeller pitch to a finer pitch in order to improve the climb capabilities of the aircraft. The pilot reported that while returning to the airport, the engine developed "a sudden and violent vibration," and he immediately elected to shut down the engine. After the propeller stopped windmilling, the pilot noticed that one of the three propeller blades had separated from the propeller hub. The pilot reported that at the airplane's recommended best glide speed, the airplane was descending at approximately 1,500 feet per minute. Knowing that he was going to be unable to reach the airport, the pilot turned the airplane towards the west in order to locate a suitable forced landing area. A forced landing was initiated into an open field located about 5.5 nautical miles west of the Double Eagle II Airport. The pilot added that during the landing on a rough and uneven terrain, the airplane touched down hard at about a 1,200 feet per minute rate of descent. The main landing gears sunk into the soft sandy soil, and the tailwheel-equipped airplane nosed over and came to rest in the inverted position. The airplane was equipped with shoulder harnesses for both occupants, and they were in use at the time of the accident. Examination of the airplane, by the FAA inspector who traveled to the accident site, revealed that the rudder, vertical stabilizer, right elevator, and both wings sustained structural damage; however, the owner reported that the airplane was "destroyed." The airplane was reported to be powered by a 115 horsepower Lycoming O-235-C1A engine. The engine was driving a 3-bladed Precision propeller which according to the pilot, had accumulated less than 3 hours since installed new on the engine. The propeller model and serial number were not provided by the pilot. The mode of failure of the propeller blade could not be determined. The 331-hour pilot reported having accumulated a total of 38 hours in the accident make and model aircraft.