On December 24, 2003, about 2030 eastern standard time, a Cessna 172RG, N4721R, registered to an individual and operated by Avion Jet Center, LLC, as a Title 14 CFR Part 91 personal flight had the right main landing gear collapse during landing on runway 27 at Key West International Airport, Key West, Florida. Visual meteorological conditions prevailed at the time, and an IFR flight plan was filed. The commercial-rated pilot and passenger received no injuries, and the airplane incurred substantial damage. The flight originated from St. Lucie County International Airport, Fort Pierce, Florida, on the same day about 1815. The pilot stated that he was cleared to land on runway 27 and when he selected to extend the landing gear, he did not get a green light to confirm all three landing gear were down and locked. He continued with the landing checklist in hope the landing gear light would illuminate. There was no light upon completion of the landing checklist, he checked the electrical fuses and performed several cycles of gear extension with no change to the indication of the landing gear position. He pumped the emergency gear extension hand pump. He informed the tower of the situation. The tower instructed him to perform several low fly-bys. Tower and fire rescue personnel visually verified that all three landing gear were down. As the airplane's main landing gear touched the runway in a soft field-landing configuration, the right main landing gear collapsed. The airplane veered off the runway to the right and came to a stop at a ditch. The pilot and passenger exited the airplane without assistance. In a later statement to NTSB, the pilot stated that he pumped the emergency gear extension pump handle until he felt resistances. He could not remember how many strokes exactly he performed, somewhere from 2 to 3 strokes. The airplane was removed from the accident site and relocated to a maintenance facility on the airport. On a later date, under NTSB and FAA supervision, the airplane was placed on jacks to perform a gear extension and retraction examination. The nose gear was isolated from the hydraulic system due to the extent of damage received in the accident. The main landing gears were operationally checked once with the airplane's own battery power and twice with the emergency landing gear extension hydraulic hand pump for manual extension of the landing gear. The main landing gears extended and locked into position within 12 to 15 pumps of the emergency landing gear extension hydraulic hand pump. No defects were observed in the operation of the extension and locking of the main landing gears by hand pump. An examination of the main landing left and right gear actuators and locking systems revealed no anomalies. Avion's chief flight instructor stated close to a month before the accident, on the accident airplane, he had to perform an emergency extension of the landing gear by the hand pump; more so, it took anywhere from 10 to 20 pumps to lower the gear and into the lock position. According to the chief pilot who checked out the pilot only verbal instructions on how to extend the landing gear by hand pump was given during the check ride in the airplane.