 As the crew performed what appeared to be an unpublished and unauthorized procedure turn for course reversal on the VOR/DME 19 approach path, they descended prematurely and hit the side of a mountain.It was subsequently determined that a southerly wind created a downdraft effect which, coupled with the aircraft's low altitude over the terrain, contributed to the crash.In their final report, issued on June 25, 1970, the NTSB determined the following official Probable Cause for the accident