TABLE OF CONTENTS The airplane is a dynamic system with six degrees of freedom, three in translation and three in rotation. In general, airplane motion is characterized by three linear and three angular accelerations under the action of gravitational, inertial, and aerodynamic and propulsive forces and moments. We will study such a dynamic system in Chapters 4 and 6. However, a significant portion of the airplane's flight envelope consists of steady flight conditions such as cruise, climb, or glide. For such flight conditions, the principles of static equilibrium can be applied. This approach can be extended to some class of maneuvers like pull-up from a dive in vertical plane or a steady turn in horizontal plane. This background will also be helpful to understand the dynamic motion of the airplane. In this chapter, we will study the basic principles of static stability and control and discuss methods that are suitable for preliminary estimation of the static aerodynamic and stability characteristics of typical airplane configurations.
Consider a ball resting on three different types of surfaces as shown in Fig. 3.1. If the ball is disturbed, it will return to its original equilibrium state in Fig. 3.1a, move away in Fig. 3.1b, and assume a new equilibrium state in Fig. 3.1c. In other words, the forces and moments acting on the ball in its disturbed state are such that they cause it to move towards its original equilibrium state in Fig. 3.1a and away from it in...
