On May 8, 1995, at 1000 eastern daylight time, a Kolb Firestar II, N47WH, was substantially damaged during a precautionary landing in Cumming, Georgia. The private pilot was not injured. The homebuilt, experimental aircraft was operated under the provisions of 14 CFR Part 91 by the pilot. Visual meteorological conditions existed at the time, and no flight plan was filed for the local, personal flight. The flight originated at a private field in Cumming at 0900. The pilot reported that the aircraft was in cruise flight when he observed unusual engine vibrations and noise. He set up for a precautionary landing in a nearby, open field. During the landing roll, the right, main landing gear struck a hidden hole, and collapsed, resulting in structural airframe damage. An examination of the Rotax 503 engine revealed that one of the spark plug leads was loose. An inspector from the Federal Aviation Administration (FAA) reported that the pilot/owner had reserved the aircraft registration number N47WH, but had not registered the aircraft. The pilot did not possess a current FAA medical certificate, nor did he have a current biennial flight review. The inspector also reported that the aircraft and engine did not have a current annual inspection.