A nozzle whose diameter can be changed. It is normally in the shape of a convergent nozzle at subsonic speeds and of a convergent-divergent nozzle at supersonic speeds, or when a reheat is on. A variable nozzle permits the use of afterburner noise reduction and easier starting. The variable geometry may be achieved automatically, depending on the throttle position and/or speed or by controlling it manually from the cockpit. On most aircraft, only the primary (convergent) nozzle position is controlled.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved