Improving Aircraft Fuel-Thermal Management

The benefits of fuel as a heat sink are well documented: less ram drag, smaller heat exchangers and ducting, and more stable temperatures. Prior to the mid-1970's use of fuel as a heat sink was fairly limited to supersonic flight, where ram air is very hot. Use of fuel to cool auxiliary oil systems (hydraulics, generators, gear boxes) throughout the entire flight envelope has been developed in the F-15, F-16, F-18, and X-29 aircraft. Adding the ECS load to the fuel-cooling system is the current focus. This has led to a large increase in the complexity and level of integration associated with fuel cooling. To make fuel-cooling effective there must be greater thermal management; this means more emphasis on load management and mission planning. The goal is to minimize the supplemental ram air-cooling needed. The integration is especially complex in a stealth vehicle which is intended for multiple mission roles. This paper reviews some suggested integration improvements from recent studies and offers additional suggestions. It also contains a discussion of thermal management The scope includes fighter and attack aircraft.