On March 24, 2012, about 1711 central daylight time, a Cessna T337B, N2334S, registered to and operated by a private individual, was landed with the landing gear retracted at the Dothan Regional Airport (DHN), Dothan, Alabama. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 personal flight. The airplane sustained substantial damage, and the airline transport pilot and one passenger were not injured. The flight originated from Enterprise Municipal Airport (EDN), Enterprise, Alabama about 1405. The pilot stated that after flying about 1.8 hours, he elected to return to EDN. When performing the “Before Landing” checklist he moved the landing gear selector handle to the down position but the landing gear did not fully extend and lock into position. He also attempted to lower the landing gear by pumping it down manually using the emergency landing gear selector handle but reported after several pump strokes, feeling great resistance. He then pitched up followed by pushing the control yoke which had the desired effect of fully raising all landing gears, then attempted numerous times to extend the landing gear. He then opted to proceed to DHN, where he performed a low pass by the air traffic control tower and was informed that the landing gear was in an “unsafe” position. He climbed to altitude and again raised the landing gear by pushing on the control yoke, then returned to DHN for landing. He executed the “Gear Up Landing” procedures and landed on grass adjacent to the paved runway. The airplane slid for about 200 feet then came to rest upright. Postaccident, the airplane was raised with jacks, and an airframe and powerplant mechanic attempted to lower the landing gears using the emergency gear extension handle. The nose landing gear went into the down and locked position; however, the main landing gears came out ½ cycle before the emergency gear extension handle “…came into a hydraulic lock.” The mechanic manually pushed the main landing gears into the locked position and the airplane was lowered from the jacks. Further, the forward propeller was in the feathered position and horizontal. Inspection of the airplane by a Federal Aviation Administration inspector following recovery revealed damage to the aft engine firewall at the engine mounts. Pictures of the damage were provided to a NTSB Structures Aerospace Engineer who confirmed the depicted damage constitutes substantial damage since it affects the structural strength and would require major repair or replacement. The airplane owner was provided the NTSB Pilot/Operator Aircraft Accident/Incident Report, and also instructed that the NTSB wanted to take possession of the hydraulic powerpack for the investigation. The NTSB Pilot/Operator Aircraft Accident/Incident Report was not received and the hydraulic powerpack was not provided; therefore, no determination could be made as to the reason for the landing gear malfunction reported by the pilot-in-command. Review of Pilot’s Operating Handbook revealed the procedures for landing with defective main gear specify to land on a hard surfaced runway or sod runway known to be smooth and level, and to feather the front propeller and position it horizontally.