Cooling air supply system

A system for optimizing cooling air supply pressure includes a high pressure fluid source which receives bleed air from the exit of a high pressure compressor and a nozzle (36) and ejector assembly (38) for supplying fluid to a point of use at a pressure sufficient to maintain a required cooling airflow and backflow margin at the point of use, and for reducing leakage of the cooling fluid between the high pressure source and the point of use.