A modern jet aircraft has many cooling requirements-lubricant, engine avionics, engine hydraulics, fuel nozzles, airframe environmental control, and hot sections. For a subsonic or low supersonic vehicle, the air can provide a substantial portion of the cooling [1]. However, at higher velocities the cooling loads become greater and the ram air temperature rises rapidly. The fuel is utilized to make up the difference and is the primary heat sink above Mach 3. Air can still make a contribution for cooling the engine's hot sections in the Mach 3 to 4 range, but this capability diminishes and is not important above Mach 4.