TABLE OF CONTENTS In designing an aircraft, there are several guidelines available for natural frequency, damping ratio, and/or time constant for each of the dynamic modes. These guidelines are based on approximately the past half century of flying experience. Dynamic stability characteristics directly affect the "flyability" or handling qualities of an aircraft. The interface between the human pilot (with physical and mental limitations) and inherent aircraft response characteristics must allow for accomplishment of mission objectives throughout the flight envelope. Precision tasks such as landing approach, tracking, and formation flying can only be accomplished successfully if the aircraft's dynamic stability characteristics are within acceptable ranges. These ranges are usually presented in terms of the dynamic characteristics we have discussed. Of course, another aspect of acceptable aircraft handling qualities involves sufficient control authority (usually referred to as control power) to trim and maneuver the aircraft throughout the flight envelope. We will focus on acceptable dynamic stability characteristics as presented in a Military Specification (MIL-F-8785C). [1] Although this specification is no longer a requirement for military aircraft, it does provide a good reference for the designer and establishes the concept of flying qualities levels. Another specification is published for civilian aircraft in Federal Aviation Requirement (FAR) documents.
The advent of modern high-performance aircraft with high-authority control augmentation systems (F-15) and fly-by-wire control systems (F-16 and F-22) has resulted in dynamic stability characteristics that do not conform to classic first- and second-order responses. Military Standard 1797 is currently used to address these...
