Editing Propelling nozzle (section)

===Variable-area for afterburning===
The afterburners on combat aircraft require a bigger nozzle to prevent adversely affecting the operation of the engine. The variable area iris<ref>"Variable Ejector For Iris Nozzles" C. R. Brown U.S. Patent 2,870,600</ref> nozzle consists of a series of moving, overlapping petals with a nearly circular nozzle cross-section and is convergent to control the operation of the engine. If the aircraft is to fly at supersonic speeds, the afterburner nozzle may be followed by a separate divergent nozzle in an ejector nozzle configuration, as below, or the divergent geometry may be incorporated with the afterburner nozzle in the variable geometry convergent-divergent nozzle configuration, as below.

Early afterburners were either on or off and used a 2-position clamshell, or eyelid, nozzle which gave only one area available for afterburning use.<ref>"Afterburning A Review of Current American Practice" Flight magazine 21 November 1952 p648, Flightglobal Archive website</ref>