Stability of Uncontrolled. Motion

The preceding chapters have been to some extent simply the preparation for what fol­lows in this and the succeeding two chapters, that is, a treatment of the uncontrolled and controlled motions of an airplane. The system model was developed in Chap. 4, and the aerodynamic ingredients were described in Chaps. 2, 3, and 5. In this chapter we tackle first the simplest of these cases, the uncontrolled motion, that is, the motion when all the controls are locked in position. An airplane in steady flight may be sub­jected to a momentary disturbance by a nonuniform or nonstationary atmosphere, or by movements of passengers, release of stores, and so forth. In this circumstance some of the questions to be answered are, “What is the character of the motion fol­lowing the cessation of the disturbance? Does it subside or increase? If it subsides what is the final flight path?” The stability of small disturbances from steady flight is an extremely important property of aircraft—first, because steady flight conditions make up most of the flight time of airplanes, and second, because the disturbances in this condition must be small for a satisfactory vehicle. If they were not it would be unacceptable for either commercial or military use. The required dynamic behavior is ensured by design—by making the small-disturbance properties of concern {the nat­ural modes) such that either human or automatic control can keep the disturbances to an acceptably small level. Finally the small-disturbance model is actually valid for disturbance magnitudes that seem quite violent to human occupants.

Leave a reply

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>