A gas turbine engine comprising: a first shaft ; a first turbine that drives the first shaft ; a fan driven by the first shaft via a speed change mechanism ; a second shaft rotatable relative to the first shaft ; a control unit ; a second turbine configured to drive the second shaft , the second turbine including at least one stage comprising a plurality of turbine vanes adjacent a plurality of turbine blades , and wherein the plurality of vanes includes at least one variable vane movable between an open position during a take-off condition and is selectively closed as the aircraft progresses to a cruise condition; the control unit is configured to move the at least one variable vane based on a temperature at a predetermined engine operational condition, and characterised in that : the predetermined engine operational condition comprises a takeoff condition, the variable vane is configured to be in the open position during take-off conditions when the temperature exceeds a predetermined temperature level, and the variable vane is configured to be in the closed position during cruise conditions; and further characterised in that the control unit is configured to control variable vane position based on inputs comprising at least fuel flow and ambient temperature to provide an output to control temperature at one or more desired engine locations. a first shaft ; a first turbine that drives the first shaft ; a fan driven by the first shaft via a speed change mechanism ; a second shaft rotatable relative to the first shaft ; a control unit ; a second turbine configured to drive the second shaft , the second turbine including at least one stage comprising a plurality of turbine vanes adjacent a plurality of turbine blades , and wherein the plurality of vanes includes at least one variable vane movable between an open position during a take-off condition and is selectively closed as the aircraft progresses to a cruise condition; the control unit is configured to move the at least one variable vane based on a temperature at a predetermined engine operational condition, and characterised in that : the predetermined engine operational condition comprises a takeoff condition, the variable vane is configured to be in the open position during take-off conditions when the temperature exceeds a predetermined temperature level, and the variable vane is configured to be in the closed position during cruise conditions; and further characterised in that the control unit is configured to control variable vane position based on inputs comprising at least fuel flow and ambient temperature to provide an output to control temperature at one or more desired engine locations. the predetermined engine operational condition comprises a takeoff condition, the variable vane is configured to be in the open position during take-off conditions when the temperature exceeds a predetermined temperature level, and the variable vane is configured to be in the closed position during cruise conditions; and further characterised in that the control unit is configured to control variable vane position based on inputs comprising at least fuel flow and ambient temperature to provide an output to control temperature at one or more desired engine locations. <EOS>