A variable vane control system for controlling the angle of rotation of a circumferential row of variable vanes of a gas turbine engine. The control system includes a mechanical linkage operable to rotate the variable vanes, one or more actuators for operating the linkage and one or more position sensors for detecting the respective actuation positions of the one or more actuators. The control system further includes a linkage position signalling switch for signalling that the mechanical linkage is at a calibration position corresponding to a predetermined rotation angle of the vanes. The control system further includes a controller for controlling the one or more actuators and thereby controlling the angle of rotation of the vanes, based on the detected actuation positions which the controller correlates with vane rotation angle. The controller further corrects the correlation between the detected actuation positions and vane rotation angle on receipt of a signal from the linkage position signalling switch indicating that the mechanical linkage is at the calibration positionvanes.