On July 18, 1998, approximately 1452 mountain daylight time, a McCarty Avid Magnum experimental-category airplane, N64KM, was substantially damaged in a loss-of-control accident on landing on runway 13 at Kalispell City Airport, Kalispell, Montana. The two aircraft occupants, both commercial pilots and certificated flight instructors, received minor injuries. The 14 CFR 91 flight was a local flight out of Kalispell. Visual meteorological conditions existed and no flight plan had been filed for the flight. The pilot reported that the aircraft, which was equipped with fixed conventional landing gear, "ground looped well into [the] landing rollout" at an estimated speed of 35 MPH (NOTE: according to a commercial reference source, the aircraft's landing-configuration stall speed is 36 MPH, and the airplane is capable of a 200-foot landing roll.) He reported that at the time, winds were from approximately 100 degrees at approximately 10 knots, gusting to approximately 15 knots (calm winds were reported at Kalispell's Glacier Park International Airport, 9 nautical miles north-northeast of Kalispell City Airport, in a 1456 hourly observation.) In a diagram of the accident sequence drawn by the pilot on his NTSB accident report narrative, the pilot indicated that the airplane departed the left side of the runway during the accident sequence. The pilot indicated on his NTSB accident report that no mechanical failure or malfunction was involved in the accident. According to a statement provided by the second aircraft occupant/pilot to FAA investigators, the aircraft owner, who had also built the aircraft, was flying the airplane from the left seat at the time of the accident, with the second pilot in the right seat. The second pilot told investigators that at the time of the accident, there was a quartering crosswind from the west. The second pilot stated that on landing, the aircraft began to veer to the left with the right wing starting to lift. The second pilot stated that he then began telling the pilot flying to get the nose straight and lower the wing, and then repeated his instruction to get the nose straight. The second pilot stated that at this point, the aircraft veered sharply to the left and tipped. The aircraft slid another 50 feet sideways, then tipped the rest of the way, striking the right wing tip and stopping abruptly. Kalispell City runway 13 is a 3,600 foot long by 60 foot wide asphalt runway. A fly-in was in progress at the airport at the time of the accident, and a temporary air traffic control tower was in operation (the airport is normally non-towered.) According to the 1998 Montana state airport directory, the airport is equipped with a windsock located adjacent to a parallel taxiway to the east of the runway at approximately midfield.