On May 25, 2000, at 1040 mountain daylight time, a Cessna T210M, N761VZ, registered to and being flown by a private pilot, sustained substantial damage when the right gear collapsed during the landing touchdown and rollout on runway 28L at the Boise Air Terminal, Boise, Idaho. The pilot was uninjured. Visual meteorological conditions existed and a VFR flight plan was in effect. The flight, which was personal, was operated under 14CFR91, and originated from Aberdeen, Idaho, at 0910, on the morning of the accident. The pilot reported in a written statement (ATTACHMENT P-I) that he departed Aberdeen, Idaho, and had an uneventful flight to Boise. After lowering the landing gear, and while on short final, the tower advised the pilot that his landing gear did not appear to be locked down. The pilot executed a go-around, recycled the landing gear and then returned for a fly-by past the tower during which one gear was confirmed visually to still be in a partially extended position. The pilot left the pattern, flew south of the airport, and attempted to correct the situation by troubleshooting and ultimately adding all the hydraulic fluid from a one-half pint container he kept in the aircraft cabin for emergencies, but this did not correct the problem. He then re-entered the pattern, executed another flyby to verify the hung gear condition and then executed a power-off, full flaps landing to runway 28L. The aircraft touched down and gradually veered off the right side of the runway coming to rest with the nose pointed east. An inspector from the Federal Aviation Administration's (FAA) Boise Flight Standards District Office (FSDO) reported that the aircraft touched down about 3,000 feet beyond the runway threshold. The right gear collapsed upon touchdown and the aircraft gradually skidded off the right side of the runway. The inspector reported that the right horizontal stabilizer had sustained damage during the ground slide. Initial examination of the landing gear system revealed a hydraulic leak. The gear were operated by means of an electrically actuated, electrically driven, hydraulic pump. The emergency extension system utilized manual pressure through the same hydraulic lines. The pilot reported in a telephone interview that he had never seen any evidence of hydraulic leakage associated with the aircraft's landing gear system. A Malfunction or Defect Report (FAA Form 8010-4) was submitted by the fixed base operator who examined the aircraft following the accident. The form reported that "the hydraulic hose failed between the system and the nose gear door actuator, resulting in system fluid depletion. The R/H [right-hand] main gear could not be extended..." and that "maintenance is unable to determine the date of manufacture of the hose (no date code)..." (refer to ATTACHMENT MDR-I).