Air Cycle Machine (ACM) is used in electronic POD’s that are assembled to aircrafts, to provide cooling for electronic equipment. When flying, RAM air that has relatively high pressure and temperature is cooled in turbine by expansion. Cooled air used in air & air heat exchanger or liquid & air heat exchanger to cool electronics. Mechanical power that is extracted from turbine is used to operate compressor that evacuate air from pod to outside. Because of high speed of turbine and compressor, optimization is done about cricital speed and bedding. Thus, reliable and longlife cooling is provided at different altitudes and different flight velocities.