On June 26, 1999, at 1430 hours Pacific daylight time, a Cessna 150K, N6171G, sustained substantial damage during a hard landing at the Hesperia, California, airport. The rented airplane was operated by Learn to Fly Unlimited, LLC, under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, was not injured. The personal flight originated from Redlands Municipal Airport, Redlands, California, at 1320. Visual meteorological conditions prevailed, and no flight plan was filed. The pilot stated he practiced landings at Redlands, then departed for Big Bear, California. After determining that conditions at Big Bear were unfavorable, he decided to go to Hesperia. He received no response from the Common Traffic Advisory Frequency (CTAF) and proceeded on a 45-degree entry for right traffic to runway 3. Prior to turning downwind, he observed the windsock at the east end of the field indicating the wind was almost directly down runway 21. He flew over the runway and turned left to enter left traffic for runway 21. The pilot stated he was established on final at 60 miles per hour with 30 degrees flaps and a 500-foot per minute sink rate, but decided he was high and increased the flaps to 40 degrees. He felt the approach was progressing normally. While crossing a road on the east perimeter of the airport, he experienced turbulence, which he characterized as light to moderate chop. He thought the sink rate momentarily increased as he began to flare and observed his airspeed was 60 miles per hour. As he completed the flare, he felt the sink rate stop as expected. He stated the airplane was 10 to 15 feet above the runway when it quit flying, dropped straight down, and bounced hard on the main landing gear. Before he could respond by adding power, the nose gear hit the ground and collapsed. The airplane skidded 30 to 35 feet before coming to rest off the left side of the runway.