An air supply controller is configured to supply cooling air to an air cycle machine. The controller includes a chamber having a first inlet configured to receive air from a first source, a second inlet configured to receive air from a second source, and an outlet configured to pass air from first inlet and/or the second inlet to an air cycle machine. A control member is disposed within the chamber and configured to move from a first position to a second position. When the control member is in the first position it obstructs an airflow from the second inlet to the outlet and permits an airflow from the first inlet to the outlet. When the control member is in the second position it obstructs the airflow from the first inlet to the outlet and permits the airflow from the second inlet to the outlet.

An environmental control system including a turbomachine assembly having a shaft, motor, turbine and compressor, the compressor outputting a compressed air stream, a first valve that splits the compressed air stream into first and second compressed air streams, a heat exchanger to cool the first compressed air stream and output a cooled air stream, a second valve positioned to receive the cooled air stream and split the cooled air stream into first and second cooled air streams, wherein the first cooled stream is expanded in the turbine to produce an expanded air stream that is combined with the second compressed air stream and the second cooled air stream to provide a combined air stream having a temperature and a flow rate, and a controller that communicates control signals to the compressor, motor and first and second valves to control the temperature and flow rate of the combined air stream.