On April 29, 2006, about 1309 Pacific daylight time, a Beech C24R, N2074P, landed with the gear retracted at Mc Clellan Airfield, Sacramento, California. The owner operated the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, was not injured; the airplane sustained substantial damage. The personal flight departed Sacramento Executive Airport, Sacramento, about 1300, with a planned destination of Mc Clellan Airfield. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot submitted a written statement. As he was entering the traffic pattern he heard a transmission from a Cessna that was making an intersection takeoff. He looked down and noted the departing airplane's location. When he looked back into the cockpit, he verified that he was within flap operating range, and lowered the flaps to 15 degrees. He reported that he was on downwind for landing on runway 16. He began a slow descent from pattern altitude and reported the base leg turn. He placed the flaps full down while making his turn onto final, and radioed that he was on final. The pilot stated that he did not retard the throttle to idle, and that the landing gear warning horn did not sound. He proceeded with the landing and did not realize that the landing gear was not down until the propeller started "banging on the runway." He made a radio call warning other aircraft in the area that he had made a gear up landing. He shut the airplane down and then noticed a little smoke coming from the right side of the cockpit. He took off his seatbelt, opened the left door, and climbed out of the airplane. He used his cell phone to call Mc Clellan Jet Services, and they notified him that the fire department was en route to his location. A sling lifted the airplane, and the landing gear was manually extended using the landing gear handle inside the cockpit. The airplane was then towed to the Mc Clellan Jet Services hangar. The pilot stated that the airplane and engine had no mechanical failures or malfunctions during the flight. The National Transportation Safety Board investigator-in-charge interviewed the pilot, who stated that he had become distracted while looking for the departing airplane, did not use his checklist, and forgot to lower the landing gear.