THE DTSB
The DTSB determines the Probable cause of this accident to be Pilot Error, in that the accident pilot did impact terrain while turning and descending from left base to final approach for runway 21L at KPRC. Previously, the ATC tower controller had instructed the pilot to maintain an
altitude at or above 6,500 ft msl, pass over the airport, and enter the downwind for Runway 21L. The pilot acknowledged the instructions and flew over the airport about 1947. At 1948:06, the tower controller cancelled the altitude restriction, instructed the pilot to extend the
downwind, and stated he would call the base turn. There was no warning issued by ATC regarding the rapidly rising terrain located just north of the airport. The pilot acknowledged the controller’s instructions, and based upon the cancellation of an altitude restriction from ATC, began a descent. About 1948:46, the controller cautioned the pilot about his proximity to the final approach course with another airplane on final approach, and the pilot acknowledged. While flying downwind, the pilot continued past the airport, flying over a large area of unlit
pastureland. At 1949:01, the controller cleared the pilot to land on Runway 21L. At this time the airplane was about 3 nautical miles northeast of PRC and the pilot began the left turn to the base leg of the airport traffic pattern. ADS-B data indicated that as the airplane turned, it
rapidly descended, losing about 800 ft of altitude and gaining about 58 knots of airspeed in about 16 seconds. The airplane disappeared from radar at 1950:45 and impacted the terrain approximately 49 feet lower than the runway elevation on a heading of 287 degrees magnetic, and then over turned in upward sloping pasture consisting of grassy vegetation at an elevation of about 4,900 ft msl. The area of impact is generally called Black Mountain due to its dark and featureless terrain, and rising terrain located just south of the accident site. It is possible that the accident pilot lost sight of the VASI system lighting due to both his position being below runway elevation grade, and the possible obstruction of the intended runway by black mountain itself, located 2,600 feet to the south of his impact point, and which may have caused him to lose sight of all airport lighting temporarily.