On March 15, 1993, at 2040 Mountain standard time, a Cessna U206G, N733TH, operated by the pilot, experienced a loss of electrical current during a nighttime cross country flight. The pilot made a precautionary landing on an unlighted runway at the Laguna Army Airfield, Yuma Proving Ground, Yuma, Arizona. During roll out, the airplane collided with rough terrain and was substantially damaged. Visual meteorological conditions prevailed during the personal flight. The airline transport certificated pilot and four of the five passengers were not injured. The fifth passenger sustained minor injuries. The flight originated from Guaymas, Mexico, on March 15, 1993, at about 1630. In the pilot's completed "Aircraft Accident Report," NTSB Form 6120.1, he wrote, in pertinent part, the following: "...I experienced an alternator failure....I made two passes over the runway I intended to land on. After exercising particular caution to possible obstacles I chose to select a descent angle to the runway slightly steeper than normal, touching down at about half length, during the flare and landing roll it was difficult to see the runway...." During the airplane's landing roll out, it collided with a runway light. Thereafter, the airplane overran the departure end of the runway and came to a stop in a ditch. An examination of the airplane's maintenance records and electrical system revealed that on March 13, 1993, Konski Air, Van Nuys, California, had certified its completion of an annual inspection. The airplane's owner reported that he authorized the pilot to fly the airplane to Mexico between March 13 and 15, 1993. The accident occurred during the pilot's return flight from Mexico after the airplane had been operated for about five hours. An FAA airworthiness inspector reported that its examination of the airplane revealed nothing unusual except that the alternator drive belt was found "extremely loose."