Abstract: A flywheel rotary engine power plant comprises a flywheel having internal passages through which power fluid is conducted to impart rotation to the flywheel about an axis. The flywheel is mounted on a journaled shaft and the pressure fluid is conducted through the shaft and introduced into a central region of the flywheel. The passages extend generally radially outwardly from the center of the flywheel. Each passage comprises a straight entrance section which merges into a single turn helix section of approximately 315.degree. extent and the helix section in turn merges into a straight exit section which extends to the passage outlet at the perimeter of the flywheel. The exiting fluid is directed against a vaned casing surrounding the perimeter of the flywheel to add a jet-propulsion effect. The propulsive force is developed by the action of the fluid on the single turn helix chambers and the jet-propulsion effect.