Abstract: A turbine blade assembly including an airfoil portion, a root portion and a cooling air plenum tube. A cooling air flow path is formed in the root and airfoil portions of the blade and has first and second inlets and an outlet formed in the bottom of the root. The plenum tube has an open front end that forms a first supply port for receiving a flow of cooling air. Openings in the tube upper portion form first and second discharge ports and a second supply port. An open rear end of the tube forms a third discharge port. A baffle assembly within the plenum tube forms first, second, and third chambers and first and second passages. The first chamber receives cooling air from the first supply port and directs a first portion to the first discharge port, which then directs it to the first inlet of the cooling air flow path. The first chamber directs a second portion of the cooling air to the first passage which, in turn, directs it to the third chamber.