Flight in mountainous terrain requires special attention to the forecasted weather, especially when it involves turbulence. In the mountains even moderate turbulence can prove devastating. On April 9, 1994 a CFI and his instrument student learned this first hand when the Cessna 172 they were flying crashed in the mountains of California. The CFI was killed and the student seriously injured.
The student obtained two weather briefings from Flight Service for a flight from Chandler, Arizona to Carlsbad, California with a stop in Yuma, Arizona. During both briefings, the student was advised of "frontal activity, gusty winds, and moderate turbulence forecast below 15,000 feet across the entire route."
While enroute the flight encountered cloud build-ups while approaching the Julian VORTAC at 8,000 feet MSL. While tracking inbound on V 458 to the Julian VORTAC, the student was unable to maintain altitude due to downdrafts. He recalls seeing the vertical speed indicator showing a 2,000-foot per minute descent. The CFI took control of the aircraft and attempted to climb, but was unable to gain or maintain altitude.
When the instructor advised San Diego TRACON that they were unable to maintain altitude, TRACON cleared the flight to maintain 7,000 feet. Two minutes later, the pilot advised TRACON that they were descending through 6,300 feet and still in the downdraft. TRACON advised the pilot of a low-altitude alert and asked him to maintain 7,000 feet. The pilot then asked for radar vectors, however the flight was below minimum vectoring altitude, so radar vectors were impossible.
After another minute, the flight was at 5,900 feet, and still descending. TRACON then advised the pilot to fly heading 280 and to climb as high as possible. There was no reply. The aircraft wreckage was found on the northeast face of California's Volcan Mountain at 4,800 foot.
Witnesses staying in a cabin 400 yards from the accident site reported winds in excess of 60 mph at the time of the accident.
The NTSB determined the cause of this accident to be the improper planning/decision by the pilot(s).
Briefings are sometimes inaccurate, however when flying in the mountains any forecast of turbulence must be taken seriously. Conditions can deteriorate extremely fast, thus both plane and pilot must be able to handle the worst-case scenario. If either cannot, the flight should be postponed until the conditions improve or cancelled.
Its possible that pilot reports (Pireps) could have helped these pilots make a more informed decision. For more information on Pireps and how to give them, take ASF's SkySpotter ® online course.
This accident report as well as others can be found in ASF's Online Database.
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