Acceleration control in multispool gas turbine engine

A gas turbine engine system comprises a first compression stage (54); a second compression stage (53); a combustor (55); a controller (102); a first sensor (82) for sensing the speed of the first compression stage (54) and providing a first indication of the sensed speed to the controller (102); and a second sensor (84) for sensing the speed of the second compression stage (53) and providing a second indication of the sensed speed to the controller (102), wherein the controller (102) is operable to control the supply of fuel to the combustor (55) in dependence upon the first indication received from the first sensor (82) and the second indication received from the second sensor (84). This arrangement is particularly useful in controlling the acceleration of an aero-engine from minimum idle.