NTSB Factual Report

On February 13, 2010, about 0830 mountain standard time, a Cessna 680 airplane, N606CS, was substantially damaged during an encounter with turbulence while in cruise flight near Eagle, Colorado. The two airline transport pilots were not injured. The airplane was owned by DEC Leasing, LLC, and operated by Citationshares Management, LLC. Visual meteorological conditions prevailed at the time of the accident and an instrument flight rules (IFR) flight plan had been filed for the 14 Code of Federal Regulations Part 91 repositioning flight. The airplane had departed Centennial Airport (APA), Denver, Colorado, about 0819 and was en route to Eagle County Airport (EGE), Eagle, Colorado.

The airplane was flying at 16,000 feet mean sea level (MSL) in clear air on top of lower clouds. Because of light to moderate turbulence the flight crew members reported that they requested and were cleared to climb to 18,000 feet MSL. While leveling off at 18,000 feet, the airplane encountered extreme turbulence which caused the autopilot to disengage and the flight crew members were briefly unable to keep the wings level, maintain altitude, or maintain airspeed. The extreme turbulence encounter lasted less than a minute and the airplane then made an uneventful descent and landing at EGE. A postflight inspection of the airplane revealed overstress damage that caused wrinkling and debonding of portions of the top skin on both wings.

Surface stations along the mountain range near the upset location registered high sustained winds with significant gusts during the times surrounding the event. Wind speeds approached 40 knots with gusts at 50 knots. Directions of the winds were generally perpendicular to the orientation of the mountain range.

An Airmen's Meteorological Information (AIRMET) in-flight weather advisory, issued at 0145, was active for moderate turbulence, icing, and mountain obscuration for the upset location and altitude. Low Level Significant Weather charts, valid during the time surrounding the accident, advised of moderate or greater turbulence below 20,000 feet for the accident region. Numerous aircraft in the area relayed turbulence information that indicated a significantly turbulent atmosphere over the central portion of Colorado during the times surrounding the accident. Pilot reports in the area near the time of the turbulence event indicated moderate levels of turbulence above 10,000 feet.

A copy of the preflight weather briefing for the accident flight was provided by the operator. This briefing, accessed via FlightPlan.com, included winds aloft estimates, surface observations, station forecasts, notices to airmen (NOTAMS) and pilot reports (PIREPS) for selected sites. The preflight weather briefing did not include available information about active AIRMETS, recent PIREPS, or Low Level Significant Weather (SIGWX) charts.

NTSB Probable Cause

The airplane’s encounter with localized severe to extreme mountain wave turbulence which resulted in substantial damage to both wings.