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Aircraft subsystem and engine heat loads are increasing at a rapid rate.1 Fuel is used in integrated aircraft thermal management systems to cool aircraft subsystems and the engine lubricating oil. All current U. S. fighter aircraft circulate fuel on the airframe to match heat loads with available heat sink. Future aircraft will be required to circulate fuel in excess of that required for propulsive energy through the airframe and engine to assure component life and integrity. These thermal stresses push current fuels JP-4 and JP-8 to bulk fuel temperatures as high as 163°C at the inlet to the mainburner fuel nozzles and to wetted wall temperatures of 205°C inside the fuel nozzle passages.2 At these conditions, engine fuel nozzles, afterburner spray assemblies and manifolds are plugging, causing increased maintenance and cost. In some instances fuel degradation changes the spray pattern in the combustor or afterburner leading to damage to engine components.

In the Middle 1970's, the Air Force identified significant damage and losses due to noncombat hydraulic fluid fires. As a result of these fires, a search for a nonflammable hydraulic fluid for use in new aircraft was initiated. A nonflammable fluid, (CHLOROTRIFLUOROETHYLENE, CTFE), was identified, however, its weight was over 2.2 times heavier than conventional fluid. This paper discusses the system design approaches, component design, and test results of an overall program to establish technology for use of this nonflammable fluid in new aircraft. This will include the tradeoff study results for selection of 8000 psi as the pressure level, design approaches to control water hammer pressures, component and system design and evaluation. The status of ongoing programs for investigating dynamic seals, pumps, and low energy consumption hydraulic concepts will also be presented.