On July 29, 1993, at about 1500 hours Pacific daylight time, a Cessna 150M, N45138, lost control and crashed while executing a landing on a privately owned ranch airstrip near Santa Margarita, California. The pilot was conducting a visual flight rules personal flight to San Luis Obispo, California. The airplane, registered to and operated by the pilot, sustained substantial damage. The certificated commercial pilot/certified flight instructor, the sole occupant, sustained serious injuries. Visual meteorological conditions prevailed. The flight originated at Santa Monica Airport, Santa Monica, California, at about 1100 hours and landed at Van Nuys Airport (VNY), Van Nuys, California; the flight departed Van Nuys at about 1200 hours. The pilot reported in a telephone interview, conducted on August 2, 1993, that he did not recall any of the events preceding the accident. He could not remember where the crash occurred. The pilot indicated on the Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2, that he normally flew to San Luis Obispo using pilotage techniques. During the flight he observed the unpaved/unpublished airstrip. He only recalls descending toward the airstrip to get a better look at it. The on-scene investigation was conducted by the Federal Aviation Administration. The reporting inspector reported that the airplane crashed about 200 feet southeast of the airport center. He also said that the propeller damage was consistent with power being applied. Photographs provided by the inspector indicate the airplane collided with the terrain in about a 30 degree left wing down and about a 45 degree nose down attitude. The landing flaps were found fully extended.