A controller assembly comprises an electromechanical actuator and a single-stage pneumatic flow switch configured to thermally protect the electromechanical actuator by a supply of cooling fluid. The single-stage pneumatic flow switch is movable between a first mode in which the switch is configured to open a cooling fluid flow passage and a second mode in which the switch is configured to close the cooling fluid flow passage. The electromechanical actuator is coupled to a valve movable between an open and a closed configuration.