On July 11, 2004, about 1135 Pacific daylight time, a Cessna 182A, N4094D, experienced a nose gear collapse while landing at the Petaluma Municipal Airport, Petaluma, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The certified flight instructor and one passenger were not injured; the airplane sustained substantial damage. The personal cross-country flight departed Napa County Airport, Napa, California, about 1100, with a planned destination of Petaluma. Visual meteorological conditions prevailed, and a flight plan had not been filed. In a written report, the pilot stated that he was attempting to land on runway 29 in light headwind conditions. After completing a normal approach, the airplane crossed over the runway threshold, and the pilot configured the airplane in a flare. The main landing gear touched down normally, and the pilot lowered the airplane's nose. As the nose landing gear touched down on the runway surface, about 200 feet down the runway from the initial touchdown point, the nose gear fork separated from the lower strut, resulting in the nose impacting the runway. The pilot further added that upon touchdown there did not appear to be any excessive G-forces or anything abnormal about the flare. The airplane incurred damage to the underside of the fuselage, the nose gear, and the propeller. In a telephone conversation with a National Transportation Safety Board investigator, the passenger, who is also a private pilot, stated that the approach was normal and properly aligned on the runway centerline. The airplane touched down on the main landing gear, and, as the certified flight instructor lowered the nose, the nose landing gear departed the airplane. The owner of the maintenance facility that inspected the airplane after the accident occurred reported to a Safety Board investigator that during the examination he found two gouges in the nose tire. The gouges were inside the treads and extended about 3 inches. He removed the tube inside the tire, and discovered pieces of the wheel had penetrated the tire, and as a result, completely destroyed the tube. He noted that while repairing the airplane he discovered damage to the firewall. The Federal Aviation Administration inspector that responded to the accident stated that an examination of the nose tire revealed a flat spot and several cuts surrounding it. He spoke to several witnesses who reported seeing the airplane bounce upon touchdown and continue to "porpoise" down the runway.