On December 8, 1993, at 0800 hours mountain standard time, an experimental Rotorway Exec-90 helicopter, N89678, crashed during takeoff at Stellar Airpark, Chandler, Arizona. The pilots were conducting a local visual flight rules (VFR) instructional flight. The helicopter, operated by Rotorway Aircraft Inc., Chandler, Arizona, sustained substantial damage. The certificated commercial pilot/certified flight instructor (first pilot), and the certificated private pilot/dual student (second pilot), received minor injuries. Visual meteorological conditions prevailed. The helicopter is equipped with a moveable ballast weight. When the helicopter is occupied by two pilots, the weight must be placed in an aft, stowed position along the longitudinal axis of the aircraft. When the helicopter is occupied by one pilot, the ballast weight is positioned on the front portion of the right landing gear skid tube. The proper positioning of the ballast weight is required to ensure that the helicopter's center of gravity (CG) limits are not exceeded. The first pilot reported that he was providing helicopter instruction to the second pilot on a taxiway at the south end of the airport. The first pilot positioned the ballast weight on the right skid tube and the second pilot began practicing solo hovering maneuvers. The first pilot then boarded the helicopter for a verbal critique, and then requested that the second pilot fly back to the company building. After takeoff, the helicopter pitched forward and the first pilot attempted to gain control of the aircraft by holding full aft cyclic pressure. The nose of the helicopter and the main rotor blades contacted the ground. The helicopter then rolled over onto its left side. An airworthiness inspector, Federal Aviation Administration, Flight Standards District Office, Scottsdale, Arizona, reported that the ballast weight was improperly positioned on the right skid of the helicopter that is normally utilized when the helicopter is flown by one pilot. The first pilot holds a commercial pilot certificate with airplane single-engine land, rotorcraft helicopter, and instrument airplane ratings. In addition, the first pilot is a certificated flight instructor with a rotorcraft helicopter rating. The most recent second-class medical certificate was issued to the pilot on April 8, 1992, and contains the limitation that the pilot must wear correcting lenses for far vision. According to the pilot/operator report submitted by the pilot, his total aeronautical experience consists of 1,941.7 hours, of which 212.2 were accrued in the accident helicopter make and model. In the preceding 90 and 30 days prior to the accident, the report lists a total of 100.5 and 32.6 hours, respectively, flown. The second pilot holds a private pilot certificate with an airplane single-engine land rating. The most recent third-class medical certificate was issued to the pilot on December 1, 1992, and contains the limitation that the pilot must wear correcting lenses. The second pilot reported that his total aeronautical experience consists of 558.4 hours, of which 15.1 hours were accrued in the accident helicopter make and model. In the preceding 90 and 30 days prior to the accident, the report lists a total of 7.4 and 1.7 hours respectively flown in the accident aircraft.