A spiral cooling system for cooling an aft turbine casing of a gas turbine engine. The gas turbine engine includes a turbine casing having a fore end and an aft end, a star bearing support member supporting a bearing housing and including a plurality of struts each mounted to an aft flange at the aft end of the turbine casing. The turbine casing includes an outer casing wall and an inner casing wall at the aft end defining an airflow plenum therebetween that receives cooling air at an input end opposite to the aft flange. The spiral cooling system includes a plurality of fins secured to an inside surface of the outer wall and being spaced from the inner wall that directs the airflow from the input end in a circular manner around the plenum to an output end of the plenum.