On July 29, 2001, at 1625 hours mountain standard time, a Cessna 172S, N3532T, porpoised during landing on runway 21 and collapsed the nose landing gear at the Scottsdale Airport, Scottsdale, Arizona. The airplane was owned and operated by the private pilot under the provisions of 14 CFR Part 91, and sustained substantial damage. The pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the personal flight, and no flight plan had been filed. The flight had originated at 1530. The Safety Board investigator interviewed the pilot. The pilot stated that the purpose of the flight was to practice takeoffs and landings. He had been doing closed pattern work for about an hour prior to the accident, with no mechanical difficulties noted with the airplane. The pilot stated that after the airplane touched down, it "hopped" a little, like a gust of wind had picked it up. It came back down and then "shot" up into the air. The airplane landed hard and the nose landing gear collapsed.