On October 7, 2011, about 1320 eastern daylight time, an experimental, amateur-built Wilhelm Calidus gyrocraft, N455BW, was substantially damaged during a loss of control on landing at the Thompsonville Airport (7Y2), Thompsonville, Michigan. The private pilot was not injured. The gyrocraft was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, which was not operated on a flight plan. The local flight departed about 1315. The pilot reported that this was his first flight in the gyrocraft and it was intended to be the first full flight of the required flight test operations phase. He noted that a mechanic had conducted 3 momentary flights over the runway after the gyrocraft had been completed. The gyrocraft was then transported to Michigan. The pilot stated that the takeoff seemed normal, but on the downwind leg of the traffic pattern the gyrocraft tended to roll to the right and he had difficulty keeping it level. He completed the traffic pattern and successfully touched down on the runway. However, after landing, he was unable to maintain control. The gyrocraft departed the runway pavement and rolled onto its right side. The gyrocraft sustained substantial damage to the rotor mast and fuselage. A postaccident inspection confirmed flight control continuity throughout the system. The linkage to the rotor appeared intact. The examination did not reveal any anomalies consistent with a loss of control. The pilot reported that he departed from and landed on runway 27 (2,900 feet by 75 feet, asphalt) at 7Y2. He noted that there was a south wind at approximately 5 knots at the time of the accident. Weight and balance documentation specified a maximum takeoff weight of 1,100 lbs. and a useful load (payload capacity) of 454 lbs. The documentation noted a minimum front seat occupant weight of 143 lbs. without corresponding ballast. The pilot reported a gross weight of 826 lbs. at the time of the accident. He noted that he occupied the front seat during the flight. Records indicated that the pilot's weight complied with the minimum front seat occupant weight requirement.