On May 17, 1994, at 1645 Pacific daylight time, a Rockwell Commander 112A, N1349J, was substantially damaged during a forced landing near Henderson, Nevada. The private pilot and his two passengers were not injured. Visual meteorological conditions prevailed for the personal flight. According to the pilot, he departed runway 18 and a shallow right climbing turn was initiated after the gear was retracted. A 200 rpm loss was experienced and a gradual degradation of engine power was observed without any sign of vibration, detonation, backfiring or sputtering. The loss of power continued to the point where the airplane could not maintain altitude. The pilot elected to turn towards a busy highway, but had to veer away to avoid colliding with vehicles on the highway. The airplane touched down on the left shoulder of the roadway with the landing gear extended. Prior to coming to a stop on the desert floor, both main landing gears collapsed after impacting a drainage ditch. The reason for the loss of engine power could not be determined.