90 will continuously adjust the vgdset signal until the p3error signal goes to zero as would appreciated by a person skilled in the art the correction factors described herein are exemplary the actual magnitude and form of the factors will of course vary depending on the specific engine design the vgdset signal is further processed in a conventional proportional plus integral controller pi 114 the output from the pi 114 passes through a switch 116 the switch 116 is provided to permit the control means 90 to be shut off during certain operations for example in the application for which the preferred embodiment was designed the variable diffuser vanes are only permitted to open when the engine 10 is at operating speed and the aircraft is on the ground the switch 116 receives aircraft signals through the ecu 50 and closes only when those conditions are satisfied it should be appreciated that the switch 116 is optional and can be removed from the control means 90 should for example inflight operation of the variable vane diffusers be required if the switch 116 is closed the vgdset signal passes to a function generator 118 which generates a current for the actuator 42 which in this embodiment is preferably controlled by a torque motor not shown a integrator windup protector 120 closes the loop between the generator 118 and the pi 114 in a manner familiar to those skilled in the art the protector 120 holds the magnitude of the signal from the pi 114 constant so long as the generator 118 is not generating a maximum control signal to illustrate what is happening to the engine 10 as the diffuser vanes.