On May 1, 2000, at 0818 Pacific daylight time, an experimental Morton Christavia Mark I kitplane, N1143L, registered to, and constructed and being flown by a private pilot, was substantially damaged during an in-flight collision with terrain following a loss of control while on short final to runway 34, at McNary Field, Salem, Oregon. The pilot was uninjured. Visual meteorological conditions existed, and no flight plan had been filed. The flight, which was a maintenance check flight, was to have been operated under 14CFR91, and originated from McNary Field at 0816. According to tower personnel, the pilot radioed that the aircraft had a brand new engine installed and was on a maintenance check flight. Immediately after takeoff from runway 13, the pilot declared an emergency and was cleared to land on runway 34. The controller reported that on short final the aircraft suddenly pitched nose down and impacted terrain. The airport manager examined the impact site and reported that the aircraft impacted terrain 281 feet short of the threshold, skidded up on to the runway tearing out a runway threshold light, and then came to rest along the east edge of the runway 236 feet north of the threshold. Both main landing gear were torn off and slash marks characteristic of propeller strikes were observed in the soil immediately following the initial ground impact. The pilot reported that he took off from Salem on the initial test flight for the aircraft and experienced a nose-heavy condition during climb out. He requested immediate clearance to return and land and turned back toward the field. He reported that he "needed power for control and while trying to make [a] wheel landing contacted [the] ground approximately 200 [feet] short of [the] runway end." During an interview with an inspector from the Federal Aviation Administration's Hillsboro Flight Standards District Office, the pilot reported that during his approach the aircraft was controllable as long as power was applied, and that on short final he instinctively reduced the power for landing and the nose of the aircraft abruptly pitched down. He was unable to recover control prior to the ground impact. According to the center of gravity (CG) calculations provided by the pilot/builder, the aircraft's empty weight was 1,053 pounds and its arm was 11.0 inches. The arm for the forward pilot seat was 18 inches and the arm for the forward mounted fuel tank was -15 inches. The documentation provided also indicated that the forward CG limit was 10.5 inches and the aft limit was 19.5 inches. The CG at the time of the accident was calculated for the aircraft based on the previous information, plus a weight of 170 pounds for the pilot from his most recent medical examination, and the pilot's reported total of 16 gallons of aviation fuel (96 pounds) aboard at takeoff, as follows: WEIGHT ARM MOMENT ACFT WT 1,053 lb 11 inches 11,583 inch-pounds PILOT WT 170 lb 18 inches 3,060 inch-pounds FUEL WT 96 lb -15 inches -1,440 inch-pounds TOTAL WT 1,319 lb 10 inches 13,203 inch-pounds The center of gravity under these conditions (10 inches) would lie one-half inch forward of the forward most CG limit. In a telephone conversation with the pilot/builder, he reported that after having worked up the basic aircraft CG figures he then made two changes within the aircraft. The first was the replacement of the aircraft battery with a larger unit weighing 7 pounds more than the former battery. The battery was located forward of the cockpit. The second was the replacement of the engine exhaust assembly with a newer, stainless steel system which weighed 2 to 3 pounds more than the former. These two changes would have changed the aircraft CG, making the aircraft more nose heavy. The pilot/builder reported on his submitted NTSB Form 6120.1/2 under the "Recommendation" section that "closer attention by [the] builder to COG due to heavier equipment being placed after [the] COG [was] figured - builder's failure to re-work COG figures."