Gas turbine engine fuel control systems

A gas turbine engine fuel control comprising a transducer means responsive to an operational variable of the engine and providing a feedback signal representing the acutal value of said variable, a demand signal setting means providing a demand signal representing a desired value of said variable, comparator means comparing said demand signal with said feedback signal and providing an error signal representing the error between the demanded and actual values of said variable, limit signal generating means connected to said transducer and providing a limit signal representing the maximum permitted rate of change of the variable, correction signal generator means connected to said limit signal generating means and providing a correction signal dependent at least in part on the rate of change of said limit signal, limit signal correcting means connected to said limit signal generator and to said correction signal generator means and providing a corrected signal dependent at least in part on the rate of change of said limit signal, signal selection means connected to said limit signal correction means and to said comparator means and providing a control signal which is the lesser of the error signal and the corrected limit signal, and servo fuel control means connected to the signal selection means and to the transducer means and operating to control the fuel flow to the engine such that the rate of change of said variable is determined by said control signal.