AIRCRAFT POWER PLANT WITH HYDROGEN TURBO-EXPANDER

A method of operating an aircraft power plant (112) includes: driving a load (16) onboard an aircraft with a combustion engine (14); heating a solid metal hydride (34) onboard the aircraft to cause hydrogen gas (26) to be released from the solid metal hydride (34); expanding the hydrogen gas (26) through a turbo-expander (38) to produce work; and using the work produced by the turbo-expander (38) to drive the load (16).