On August 19, 2006, at approximately 1510 mountain daylight time, a Bellanca 8GCBC (Scout), N4109Y, was substantially damaged following impact with terrain near Lower Duck Creek Rd., Townsend, Montana. The private pilot, the sole person on board, was seriously injured. The pilot/owner was operating the airplane under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the personal cross-country flight which originated from Missoula, Montana, approximately 2 hours, 10 minutes, before the accident. The pilot had not filed a flight plan. The pilot said that he was performing a fly-by at Duck Creek to find some of his friends who were camping there. A witness reported that the airplane made multiple low passes over open terrain; on the last pass, the left wing struck the ground. The airplane cartwheeled and came to rest on the ground. The pilot reported that the left wing was bent up from the mid-section outboard, and the fuselage was crushed and wrinkled.