Study of the aircraft aerodynamic characteristics at entering the clear-air turbulence zone and the flight safety issues

Shear flows in the atmosphere lead to formation of the clear-air turbulence (CAT) zones. These zones are having the characteristic horizontal size of 20 km to 2000 km and may be less than 1000 m thick making it difficult to detect them and create effective systems to find the bypass routes. Intense CAT zones could appear at the altitudes of up to 30 km and higher. The main CAT feature lies in the fact that it occurs not in the clouds, but in the clear sky with good visibility, where meteorological radar is unable to detect it, and the flight crew is unable to get prepared. Every year, about 750 cases of the aircraft entering the CAT zones are registered in the global civil aviation. This work constructs a grid solution that simulates the large-scale atmospheric turbulence based on the atmospheric profiles taken from the experiment within the framework of the boundary value problem for the Reynolds-averaged Navier – Stokes equations. On the basis of the obtained solution and within the frames of the engineering method, coherent vortex structures (CVS) are formed, interaction with which, assuming the hypothesis of the perturbed speed frozen field, makes it possible to evaluate possible increments in the aerodynamic forces and moments and to simulate a situation of the aircraft entering the CAT zones.