The airplane collided with mountainous terrain at about 1000 Pacific time and sustained substantial damage; the Private pilot and one passenger sustained serious injuries. The airplane departed the Santa Ynez Airport, Santa Ynez, Calif., at about 0900, and the pilot was planning to fly over a remote area located near the accident site. Visual conditions prevailed. The airplane was reported as missing on May 9 and an Alert Notice (ALNOT) was issued. Later that day, the airplane wreckage and its occupants were located. According to search-and-rescue personnel, the pilot reported engine problems. The pilot force-landed the airplane in the rough, mountainous terrain.