Gas Turbine Variable Exhaust Nozzle Control?

i want to know what is the variable exhaust nozzle control, the purpose or the application and maybe some example maybe....TQGas Turbine Variable Exhaust Nozzle Control?
On high performance jet aircraft, the nozzle control is under the management of an automated system. The purpose of it is to ensure maximum thrust by tailoring the convergent/divergent area during operation, especially for engines equipped with after burner.Gas Turbine Variable Exhaust Nozzle Control?
I'm not an engine guy, but this is out of the F15 manual...





09-3. Divergent Exhaust Nozzle System. The


divergent exhaust nozzle system is made up of


divergent nozzle segments, divergent seal segments,


divergent segment connecting links and divergent


nozzle brackets. The forward end of the divergent


nozzle segments are hinged to aft ends of the


convergent segments, and the outboard midpoints


are connected to the divergent nozzle brackets by


the divergent segment connecting links.





09-4. The forward ends of the divergent seal


segments are hinged to the convergent nozzle seal


segments. The divergent exhaust nozzle seeks the


best setting depending on pressure and velocity of


the exhaust gas and the velocity of airflow


surrounding the nozzle for maximum efficiency.





09-5. PRINCIPLES OF OPERATION.


09-6. Divergent Exhaust Nozzle System. The free


floating divergent exhaust nozzle system provides a


variable, divergent nozzle opening, depending on


the pressure of the exhaust gases and ambient air to


get high nozzle performance while maintaining low


external drag. The divergent exhaust nozzle system


operates independently of, but in unison with, the


convergent nozzle system to get maximum


engine/augmentor performance.
Are you talking about a Harrier jump Jet???