On June 30, 2011, about 1615 central daylight time, an experimental amateur built RV9A airplane, N59VA, experienced a partial loss of engine power on initial climb after takeoff from the Kittie Hill Airport (77T), Leander, Texas. The commercial rated pilot sustained minor injuries and the airplane sustained substantial damage during the forced landing. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. According to the pilot, following the installation of an Eggenfellner Subaru E6 engine, he flew the airplane three times before the accident flight. During the first flight, the engine overheated and the pilot returned to the airport and landed. A second flight of 30 to 45 minutes was performed maintaining higher airspeeds and the engine performed with no observed anomalies. After takeoff on the third flight, the pilot noted that the engine didn’t sound right, so he returned to the airport and landed. The pilot, along with his mechanic, examined the engine and could not locate any issues, so the pilot departed for his forth flight. After takeoff from runway 17, when the airplane reached an altitude of 200 to 300 feet, the engine lost partial power. The pilot elected to make a left turn and performed a landing to runway 30. As the airplane neared the end of its landing rollout, the nose gear impacted a depression in the turf runway and the airplane nosed over. Examination of the engine by a Federal Aviation Administration (FAA) inspector revealed that the airplane sustained substantial damage to its vertical stabilizer and damage it the left wing tip, canopy, nose gear, and propeller. Examination of the engine did not reveal a reason for the loss of engine power.