On April 27, 2006, about 1530 mountain daylight time, a Potts MA-5 amateur-built experimental airplane, N413AC, sustained substantial damage when the left main landing gear separated during the landing roll on runway 20 at Glacier Park International Airport, Kalispell, Montana. The private pilot, the sole occupant, received minor injuries. The airplane was registered to a private individual and operated by the pilot. Visual meteorological conditions prevailed and no flight plan was filed for the 14 CFR Part 91 personal local flight. According to the pilot, the airplane "pulled to the right after landing straight." He applied left rudder and brake, and the left main landing gear leg "broke off near weld 8 inches above axle." The gear leg dug into the asphalt, and the airplane nosed down. An FAA inspector examined the airplane and reported structural damage to the fuselage near the left gear attachment point. The reason for the failure of the left main landing gear was not determined.