No abstract

The paper describes an important mode of airplane flight in which the aircraft is under the joint control of a human pilot and an automatic control system. The first part of the paper describes the interaction of air loads and inertia reactions which govern the dynamic stability of the airplane, and seeks to give a physical picture of the response of the airplane to control and random disturbances. The paper then describes a research project in which the pilot’s controls were disconnected from the control surfaces, and separate servos provided both to drive the aerodynamic surfaces, and to resist the actions applied to the cockpit-controls by the pilot. The surface servos receive signals from cockpit-control motions and from a stability computer which senses airplane-body motions. Airplane response as seen by the pilot can be varied by adjusting the computer, and the pilot is unaware of the control-surface motions caused by the computer. Thus both airplane stability and control feel can be varied independently and easily in flight. Research airplanes so equipped are now being used to map out regions of acceptability for future design in the handling characteristics problem, and are incidentally demonstrating means for stabilizing existing airplanes which may be deficient in one or more respects.