Severe turbulence and maneuvering from airline flight records

Digital flight records from reported clear-air turbulence incidents are used to determine winds, to determine maneuver G loads, and to analyze control problems. Severe turbulence is found downwind of mountains and thunderstorms associated with vortices in atmospheric waves. It is also found in strong updrafts above thunderstorm buildups that are not detected by onboard weather radar. An important finding is that there are large maneuvering loads in over half of the reported clear-air turbulence incidents. Maneuvering loads are determined through an analysis of the short-term variations in elevator deflection and aircraft pitch angle. For altitude control in mountain waves the results indicate that small pitch angle changes with proper timing are sufficient to counter the vertical winds. For airspeed control in strong mountain waves, however, there is neither the available thrust nor the quickness in engine response necessary to counter the large and rapid variations in horizontal wind.