CRYOGENIC FUEL COOLED ECS PRECOOLER

Aircraft systems including a fuel tank (302) containing a cryogenic fuel, an engine (304) configured to consume the fuel, and an ECS having a precooler (308) arranged to receive the fuel and air from the engine (304). The precooler (308) includes a first heat exchanger (320) configured to receive a first state of the fuel and output a second state of the fuel and a second heat exchanger (322) configured to receive the second state fuel and output a third state fuel. The first state has a first density, the second state has a second density, and the third state has a third density, wherein the first density is greater than the second density, and the second density is greater than the third density. The engine air is directed through the second heat exchanger (322) first and then through the first heat exchanger (320).