On December 1, 1999, approximately 1730 Pacific standard time, a Beechcraft B-19, N4617M, registered to and operated by Big Bend Community College as a 14CFR91 instructional flight, was destroyed after colliding with power lines and terrain approximately three mile northeast of Grand Coulee Dam Airport, Electric City, Washington. The certified flight instructor (CFI) and student pilot both sustained serious injuries. Night visual meteorological conditions prevailed and a flight plan was filed for the cross country flight. The flight originated from the Grant County International Airport (MWH), Moses Lake, Washington, approximately one hour prior to the accident. In a written statement, the certified flight instructor reported that the intent of the instructional flight was to complete lesson 2-4 in the Training Course Outline (attached). The lesson called for a cross-country flight with a diversion to an alternate airport. After reviewing the weather and the student's flight planning, the two pilots departed MWH at 1625 Pacific standard time, with a planned destination of Anderson Field, Brewster, Washington, (S97). The instructor pilot stated that approximately 20 minutes after departing MWH he instructed the student pilot to divert to Grand Coulee Dam Airport (S97), approximately 25 miles northeast of their location. The instructor pilot and student pilot both remember making a heading change for the new destination airport. However, both pilots were unable to recall any of the detailed events between the time of the heading change and the accident. The aircraft's initial impact point was a series of tower-mounted, high-voltage transmission lines (that are displayed on the sectional chart), located approximately three nautical miles northeast of the airport. According to Bonneville Power Administration, the height of the power lines are approximately 250 feet above ground level (2,250 feet above mean sea level [MSL]). According to Douglas County Sheriff's Office, witnesses reported seeing a bright flash, in the vicinity of the power lines, at the approximate time of the accident. According to a flight navigation log recovered from the accident aircraft, the planned altitude for the cross country flight was 4,500 feet above MSL. The published elevation for Grand Coulee Dam Airport is 1,590 feet MSL. Post-accident examination of the aircraft revealed no evidence of a pre-impact mechanical failure or malfunction.