Control of a gas turbine engine

A method of controlling a gas turbine engine having in axial flow series, a booster compressor, a core compressor, combustion equipment, a core turbine, and a low-pressure turbine, the core turbine driving the core compressor via an interconnecting high-pressure shaft, the low-pressure turbine driving the booster compressor via an interconnecting low pressure shaft, and the low-pressure turbine also driving an external load having a defined speed characteristic that dictates the speed of the low-pressure turbine and booster compressor, the booster compressor having one or more rows of variable stator vanes, wherein the method includes:

• scheduling variation in the angle of the variable stator vanes as a function of the speed of the booster compressor such that the vanes open as the booster compressor speed increases;
• measuring or setting one or more operational parameters which are determinative of the temperature at entry to the core turbine;
• and
• biasing the scheduling of the angle variation of the variable stator vanes as a function of the operational parameter(s) to reduce variation in temperature at entry to the core turbine.