UA538283-2

The Servo Fuel Heater is designed to provide oil-to-fuel transfer to prevent icing of the main engine control servo fuel system, utilizing heat from the engine scavenge oil system directed over a servo fuel filled tube-core bundle.

Fuel flows through the tube-core bundle, and oil is guided over the tubes to the oil outlet port. At cold start, oil pressure is generated, which opens the bypass valve, permitting cold oil to bypass the tube core bundle and leave direct through the outlet port. As engine heat warms the oil, viscosity reaches a level where pressure falls below the bypass valve setting when the valve will close the bypass to outlet. Warm oil will then flow across the fuel filled tube-core bundle to the outlet port. Oil heat is transferred through the core bundle tube walls, into the fuel flow, to provide a controlled heat transfer for efficient servo fuel system operating conditions.