The pilot stated that, after completing a preflight inspection and reviewing weather conditions for the departure and proposed destination locations, which included winds aloft and METARs, they departed on the cross-country flight in the Cessna 182.
About 2 hours and 15 minutes into the flight, while at an altitude of about 12,500 feet mean sea level (msl), the airplane encountered severe turbulence and windshear, and shortly thereafter, a downdraft.
Unable to escape the downdraft, the pilot attempted to level the wings and pitched up as the airplane hit snow- and ice-covered terrain on the north side of Mount Hawkins in the Wrangell St Elias National Park at an elevation of about 6,570 feet msl.
During the impact, the airplane sustained substantial damage to the fuselage, wings, left horizontal stabilizer, and elevator. The pilot and passenger sustained minor injuries.
A review of flight track data revealed that, after departure, the flight proceeded to the south and climbed to an altitude of about 11,000 feet msl before initiating a left turn to the east. The flight continued on an easterly heading at an altitude between about 11,000 and 12,900 feet msl. The last in-flight data point was at 1311:19, when the airplane was at an altitude of 11,800 feet msl with a groundspeed of 108 kts and on a track of 117°.
No frontal boundaries existed near the accident site, however a relatively strong pressure gradient was present along the northern Gulf of Alaska. The National Weather Service, Anchorage, Alaska, upper air soundings from 0400 and 1600 both indicated favorable conditions for severe mountain wave conditions between 9,000 and 14,000 feet mean sea level with updraft and downdraft speeds between 2,000 and 3,000 feet per minute. These conditions would be prevalent near any mountains with tops between 5,000 and 13,000 feet msl. The mountains to the south of the accident site were between this height. The Polar Operational Environmental Satellites imagery from 1337 also showed transverse wave banding at the accident site, which is indicative of mountain waves.
FAA Advisory Circular (AC) 00-6B, Aviation Weather, describes mountain wave conditions and the associated aviation hazards: A mountain wave is an atmospheric wave disturbance formed when stable air flow passes over a mountain or mountain ridge. Mountain waves are a form of mechanical turbulence which develop above and downwind of mountains. The waves remain nearly stationary while the wind blows rapidly through them. The waves may extend 600 miles or more downwind from the mountain range. Mountain waves frequently produce severe to extreme turbulence. Location and intensity varies with wave characteristics.
Mountain waves often produce violent downdrafts on the immediate leeward side of the mountain barrier. Sometimes the downward speed exceeds the maximum climb rate of an aircraft and may drive the aircraft into the mountainside.
Probable Cause: An encounter with mountain wave turbulence and windshear that exceeded the climb capability of the airplane and resulted in impact with terrain.
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This May 2021 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Glider pilots live for wave. Avoid the rotors and avoid the down air and it is hours and hours of completely smooth rapid upward flowing air. The difference between severe turbulence and smooth air, or rapid up air and rapid down air can be a very small distance. The key is to quickly fly across the downward air, not within and parallel to it. Unfortunately, GA outside of the glider community does not train how to visually identify different parts of the wave profile, and ways to get out (or in). Rather we simply seem to collectively and simply say “it is dangerous, avoid it”.
In my experience mountain flying success is not analyzing data but rather knowing when to turn around based on what you’re feeling.
Thank God the pilot and passengers survived without injury, a testament to the pilot’s flying abilities. Imagine he had used an aircraft emergency parachute system. Would they have impacted as well?
with a parachute, I’d imagine you always impact, and with substantial damage to the aircraft. Sounds like the passengers had minor injuries…..Probably about the same report as if they’d have had a chute.