On February 12, 2001, at 2018 mountain standard time, N24PT, a Cessna 441, was substantially damaged when it collided with terrain during landing at Centennial Airport, Englewood, Colorado. The private pilot and one passenger were not injured. Visual meteorological conditions prevailed, and an IFR flight plan had been filed for the personal flight being conducted under Title 14 CFR Part 91. The flight originated at Mobile, Alabama, at approximately 1700 central daylight time. According to the pilot's accident report and a subsequent telephone interview, the pilot said he was cleared to land on runway 35L. He wrote: "(I) lowered the landing gear switch. On final I put my hand on the switch to insure it was in the down position. My wife . . . said she saw me do this." The pilot said the landing gear collapsed on touch down, and that the landing gear warning horn never sounded. A post accident examination disclosed extensive damage to the airplane's lower spar cap, and to both the left and right inboard flap tracks. The pilot also stated that during a previous flight, from Lakeland, Florida, to Mobile, Alabama, he had to cycle the flaps several times to get them to extend. After landing, he could not retract the flaps. "Both the landing gear and flaps are hydraulically operated and activated by an electrical switch," he wrote. Straight Flight, a repair station on the airport, was asked to retrieve the airplane. They submitted a report as to their findings. Upon entering the airplane, personnel noted that the landing gear handle was in the DOWN position. They said the landing gear doors were closed and they bore no damage. They reported that when the landing gear on the Cessna 441 extends and retracts, only one main landing gear moves, followed by the other main landing gear, and then followed by the nose landing gear. The airplane was lifted on maintenance jacks and the landing gear was lowered using the emergency gear extension system. The gear DOWN AND LOCKED lights illuminated. On March 6, an external hydraulic power unit was attached to the airplane's hydraulic system, and 20 fault free cycles were performed. No faults were detected. Damage to both inboard flap track assemblies precluded a similar test of the flaps.