The illustration shows a typical operation of a variable geometry exhaust nozzle. The nozzle is fully open at start up and remains in the same position till throttle is advanced to about 65% when it is fully closed. The nozzle remains fully closed until beyond 100% RPM and until minimum afterburner is selected, when it takes up an intermediate position between the maximum and the minimum. It opens up fully when throttle is just short of fully open position and remains so until the maximum afterburner position. The same sequence is followed when throttle is brought back except that the nozzle opens up to fully open position at about 60% RPM instead of 65% as was the case when throttle was being advanced.
An aircraft whose shape can be changed. The term, however, is generally used for aircraft whose sweepback can be varied in flight. See fixed geometry