High Altitude Turbulence, A U-2 Perspective

Abstract

High altitude aircraft remain an important part of the Department of Defense reconnaissance capability set. These aircraft, which fly above commercial cruise altitudes, frequently encounter a unique type of turbulence including both traditional mechanical turbulence as well as oscillatory fluctuations of temperature and horizontal and vertical wind speeds. This latter type of turbulence is attributed to gravity (or buoyancy) waves. This paper expands on previous studies by comparing simulations of a representative high flying research aircraft to a U-2 with stability derivatives and autopilot provided by the developer. The effects of wave-like behavior on these aircraft are found to produce high aircraft loads at certain frequencies. The results of this paper provide insight unique to this line of research into the performance of actual Air Force assets. The potentially detrimental effects of high altitude turbulence lead to a recommendation to carefully study of the impacts of this environment on any new aircraft design or modification.