Flight Details
A non-instrument rated private pilot departed in visual flight rules (VFR) conditions with three passengers for a 134-mile trip to a fly-in restaurant destination to celebrate a passenger's birthday. There were no records of the pilot having received weather briefings from any Federal Aviation Administration (FAA) facilities.
Route and Radar Data
Recorded radar data showed that instead of flying a direct route, the airplane meandered towards a mountain top VOR navigational aid and was about 18 miles off a direct course between the departure and destination airports. About 30 minutes into the flight, the airplane reversed course and was headed back towards the open desert departure area when radar contact was lost.
Weather Conditions
A moderate north-south surface pressure gradient produced strong, gusty northerly low-level winds over the higher elevations of the mountain range. Observations from satellite imagery indicated that mostly clear skies were present from the departure airport until the accident airplane reached the vicinity of the accident area. However, a weather satellite visible image showed that cloud cover from the northwest covered the accident site around the estimated time of the accident. Clear areas were present south and west of the VOR. Cloud bases reported around the VOR ranged from on the surface to less than 1,000 feet above ground level (agl), with tops generally 8,000-10,000 feet mean sea level (msl) in the area. No in-flight advisories (SIGMET or AIRMET) were valid for the accident location at the time of departure. However, AIRMET TANGO was updated at 1335 to include a forecast of occasional moderate turbulence below 12,000 feet over coastal mountain areas. According to pilot reports from very near the accident area around the time of the crash, moderate turbulence and up and down drafts were being experienced from 500 to 1,200 feet per minute.
Accident Sequence
While traversing a mountain range between two valleys, the aircraft collided with mountainous terrain after a likely encounter with clouds, moderate turbulence, and up and down drafts in the 500- to 1,000-foot-per-minute range. Examination of the wreckage and the accident site showed that the airplane collided with mountainous terrain while in a wings level cruise flight attitude. The autopilot switch was found in the ON position.
Terrain and Navigation
There are two small lakes in the vicinity of the VOR. Overflying one lake on the accident flight's last radar observed heading would have taken the airplane over low terrain on a route back toward the departure airport, whereas overflying the second lake on the last observed heading would have taken the airplane toward mountainous terrain that rises to 5,430 feet msl within 2 miles, which is the location of the accident site.