TABLE OF CONTENTS In previous chapters, we considered the airplane stability and control in the linear range of angle of attack based on the assumption of small disturbances in all the motion variables. Under this assumption, the longitudinal and lateral-directional motions could be decoupled and analyzed separately. Such an approach is not possible when the cross coupling between longitudinal and lateral dynamics becomes important. This type of coupling occurs because of inertia terms in the equations of motion or nonlinearities in aerodynamics. In Chapter 7, we discussed two examples of inertia cross coupling, inertia coupling during rapid rolls and airplane spin. In this chapter, we will study the stability and control problems caused by cross coupling between longitudinal and lateral-directional motions on account of nonlinearities in aerodynamics and large amplitude motions, which typically occur during maneuvers at high angles of attack approaching or exceeding the stalling angle.
Flight at high angles of attack, or even at angles of attack close to the stall angle, was recognized to be disastrous from the very early days of aviation. The Wright Brothers had experienced perhaps the first military accident in 1908 during a demonstration flight because of an inadvertent stall and loss of control. During this early period and up to the end of World War II, several accidents occurred because of inadvertent stall, loss of control, and spin. These events led airplane designers to focus their attention to the study of spinning problems with an objective to develop...
