On June 1, 1997, approximately 2240 mountain daylight time, a Cessna 402C, N1233P, impacted the terrain just after takeoff from Rawlins Municipal Airport, Rawlins, Wyoming. The airline transport pilot, who was the sole occupant, received serious injuries, and the aircraft, which was owned and operated by Casper Air Service, sustained substantial damage. The 14 CFR Part 135 cargo flight was departing for Riverton, Wyoming, and was being operated in visual meteorological conditions on a dark night. The pilot had filed an IFR flight plan. According to an FAA inspector who arrived at the scene the day after the accident, the aircraft impacted 200 foot high terrain about one and one-quarter mile off the end of runway 04, while making a VFR dark-night departure. Both propellers made a number of equally-spaced slash marks in the surface of the ground, and an inspection of the flight control system continuity showed no pre-impact anomalies. Both the flaps and the landing gear were in the up position. During the investigation, both engines and both propellers were subjected to teardown inspections. Except for impact damage, both engines and their fuel systems exhibited normal operational signatures throughout, with all components appearing well lubricated, and all magnetos producing a bright blue spark across a seven millimeter spark gap. The propeller blade visual inspections and the propeller hub teardown inspections revealed damage signatures consistent with ground impact in a flat pitch under significant power. Records provided by the operator indicate that the pilot had flown out of this airport in the past, and that at the time of departure, the aircraft was approximately 600 pounds below maximum certificated gross weight. As of the date of the last investigative interview, the pilot has been unable to remember the sequence of events leading up to the crash.