Stability and Control

The term

flying qualities

denotes primarily the combination of stability and control properties which have an important influence on the ease and precision with which a pilot can maintain a state of equilibrium and execute manoeuvres, and thereby on flight safety and operational effectiveness. The term

stability

characterizes the motion of an aeroplane when returning to its equilibrium position after it has been disturbed from it without the pilot taking action. Aircraft

control

describes the response to actions taken by a pilot to induce and maintain a state of equilibrium or to execute manoeuvres. For military aircraft, the definition of flying qualities is broadened with an assessment of the precision and effectiveness with which tasks can be performed. Qualities like agility and targeting precision are closely associated with

handling qualities

, a term which denotes the short-term dynamic response of an aeroplane as a reaction to control.

Flight dynamics

deals with the relatively short-term motion of an aeroplane in response to the pilot’s actions or to external disturbances like gusts, wind gradients, or turbulent air. In contrast to aeroplane performance, which is governed by forces along and normal to the flight path, stability and control is dominated by aerodynamic moments about the

centre of gravity

, with a rotational motion as a response to these moments.