On April 19, 2012, at 1715 eastern daylight time, a Cessna 210, N96050, experienced a main landing gear collapse on landing roll at Gatlinburg Pigeon Forge Airport (GKT), Gatlinburg, Tennessee. The airplane sustained substantial damage to the left horizontal stabilizer. The certificated private pilot was not injured. The airplane was registered to a private owner and was operating as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed and an instrument flight rules (IFR) flight plan was filed. The flight originated from Kennett, Missouri, at 1526. The pilot stated he canceled his IFR flight plan upon arrival in the vicinity of GKT and entered a right traffic pattern for landing. He completed the checklist and lowered the landing gear. He noticed the hydraulic unit stayed on and he did not have a green landing gear indication light in the cockpit. He looked outside and the nose wheel was extended, but both main landing gear were partially extended. He recycled the landing gear handle with negative results. He then attempted the emergency landing gear extension procedure several times with negative results. He contacted a mechanic over the airplane radio. He then made a fly by and they decided that he should attempt to see if the hydraulic fluid was low. The pilot initiated a climb to 3,500 feet above ground level and placed the airplane on autopilot. He went to the back of the airplane and obtained some tools and oil. He returned to the cockpit and gained access to the hydraulic fill port and poured some oil into the hydraulic fill area. He then attempted to recycle the landing gear with negative results. The airplane had about 5 gallons of fuel remaining, so he attempted some negative "G’s" with negative results. He then made a straight in approach with the nose wheel down and the main landing gear partially extended. During touchdown, the airplane veered to the left off the side of the runway and came to rest upright in a grassy area. Examination of the landing gear system revealed the landing gear down pressure hose (part number S2178-3-0144) on the nose landing gear was ruptured, which would not allow the main landing gear to fully extend and lock in the down position when the landing gear was extended with the landing gear handle or by emergency extension. Review of the Cessna Aircraft Company Series Service Manual, D20004-5-13, Revision 5, July 1, 2004, LANDING GEAR, SPECIAL INSPECTION ITEMS (19) states, "Each 1,000 hours or 5 years, inspect and replace as required, all rubber hydraulic hoses in both the retraction and brake system." The airframe and power plane mechanic with inspection authority who had been performing the inspections on the airplane for the last 3 years wrote in a statement to the NTSB investigator, "I have inspected these hoses the past 3 years they were flexible, no frying, held pressure with any leaks." There was no entry in the logbook to indicate the hydraulic hoses had been replaced within the last 5 years or 1,000 hours.