March 25, 2013
High-altitude mountain flying has always been one of the more dangerous activities GA aircraft undertake each year. On average, 17 people die annually in GA accidents in the mountains of Colorado alone. Where eastern Appalachian flyers are used to climbing over mountains in the 2,000 to 3,000 foot range, pilots in the west regularly have to navigate in areas where the base ground is over twice that height, and the mountains themselves protrude skyward to well over 10,000 feet. Not many GA aircraft have the ability to climb over such high terrain, so the only option for most GA pilots in this area is to fly through the mountain passes. This brings numerous risks with it, as the statistics show. Some of these accidents occurred because pilots would check the weather from areas outside of the pass, when the weather inside of the pass was quite different. To solve this problem, Colorado aviation authorities recently installed Automated Weather Observing Systems (AWOS) in five mountain areas and two at critical areas of the plains. There are plans for more as they can get funding. These AWOS systems are exactly like those you may find at your local airport.
While these systems help with the weather, turbulence is still difficult to detect. Winds are usually fairly high at higher altitudes, particularly following a large weather system, The wind then funnels through mountain valleys, spills through the passes' cracks and crevices, and mixes with winds from other valleys and winds coming over the mountains. This can lead to a lot of disturbed air, and some serious turbulence. Always report pireps if any encounters with mountain turbulence occur - for the safety of pilots that may be following you, and those still on the ground.
For more information on mountain flying, visit the Colorado Pilot's Association Web site.
A Piper Malibu sustained substantial damage during an encounter with turbulence while on descent near Granby, Colorado. The ATP and his three passengers were not injured. Visual meteorological conditions prevailed for this cross-country flight that originated from Idaho Falls, Idaho, approximately 1 hour 24 minutes before the accident. An IFR flight plan had been filed.
According to the pilot, "the flight had been uneventful to that point." He said that "he felt the nose tuck a little and then wham — they hit severe/extreme turbulence." The 5 second event rolled the airplane into a 90 degree right bank, and a pitch up attitude of 45 degrees. The pilot reported that his airspeed indicator was reading 140 knots, and his altitude was 15,700 feet at the time of the event. He calculated his maneuvering speed to be approximately 120 knots.
Radar data indicated that the airplane gained 500 feet of altitude in 5 to 6 seconds. Additionally, the radar ground tract indicated that the airplane was over Corona Pass when the event happened. Both wings and horizontal stabilizer had to be replaced.
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