On November 29, 2013, about 1500 Pacific standard time, a Cessna 210, N6575X, was substantially damaged during landing at the Florence Municipal Airport (6S2), Florence, Oregon. The airplane was registered to a private individual and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The airline transport pilot and his passenger were not injured. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight. The local flight originated from 6S2 about 1400. The pilot reported that prior to the flight, the landing gear actuator was rebuilt and all subsequent ground tests were uneventful. The pilot and passenger proceeded to conduct a local maintenance test flight. During the flight, the landing gear retracted normally, however, when it was extended, the left and right main landing gear would not extend. The pilot stated that the nose wheel landing gear was extended and locked in the down position, and that despite numerous attempts he was unable to raise or lower the landing gear. The pilot initiated a partial gear up landing to Runway 33. During the landing roll the left horizontal stabilizer struck the runway. Postaccident examination of the airplane by the pilot revealed that the left horizontal stabilizer and elevator were bent upward about 10 degrees. The airplane was recovered to a secure location for further examination. Examination of the airframe by a Federal Aviation Administration (FAA) inspector was conducted on December 19, 2013, at the owner's hangar. The airplane was placed on jacks and a hydraulic mule was attached to the hydraulic system. Despite multiple attempts, the landing gear would not retract or extend. The hydraulic power pack was subsequently removed and retained for further examination. The hydraulic power pack, part number EA1332-1, serial number 699, was examined by APPH, Wichita, Kansas, under the supervision of an FAA inspector. The examination revealed that all safety wire was intact and no evidence of system contamination was found. The power pack was placed on a test bench and functionally tested using the Cessna 210 Service Manual instructions. During the test, the system would allow the landing gear to be extended, however, would not allow the flaps to be extended or retracted. In addition, the unit did not allow the landing gear to be retracted or build up any pressure with the hand pump. Further examination of the hydraulic pack revealed that the number one thermal relief valve lost pressure after it was relieved. Four poppet assemblies did not retain pressure during the test. In addition, the hand pump assembly spring was not correct for the make/model hydraulic power pack. No additional anomalies were noted during the examination. Review of the maintenance logbook records for the airplane revealed that an entry dated April 8, 2013, at tach time of 1,854.9 hours and airframe total time of 1,885.7 hours, stated in part "….repaired leak in hydraulic power pack." No further entries were noted within the logbook regarding the hydraulic power pack.