the pilot was flying to a high altitude lake (elevation 11,300 feet) to aerially plant fish for the State of Colorado. The winds at the lower altitudes were calm. At 11,429 feet, data collected from an onboard GPS recorder, indicated that the airplane performed an abrupt 90 degree turn to the left, and impacted the adjacent ridge. Three other Colorado State pilots, flying the same mission in the area, reported wind shear and moderate turbulence from 11,500 to 12,500 feet. The density altitude was calculated to be 12,350 feet.