Abstract: An external cooling system for hydraulic fluid of an aircraft hydraulic system. The external cooling system includes a heat exchanger, where an input side of the heat exchanger is connected to a hydraulic fluid reservoir of the aircraft hydraulic system and an output side of the heat exchanger is connected to suction ports of a return side of an electric motor driven pump (EMDP) of the aircraft hydraulic system. The external cooling system operates on 120 VAC power and the hydraulic fluid does not exceed a maximum pressure of 50 pounds per square inch gauge. The EMDP pumps hydraulic fluid through the hydraulic system under conditions wherein fuel tanks in the aircraft are empty, and the external cooling system cools the hydraulic fluid as the EMDP pumps the hydraulic fluid, wherein the hydraulic fluid passes from the hydraulic fluid reservoir and through the external cooling system before entering the EMDP.

Abstract: A method of cooling hydraulic fluid for an aircraft hydraulic system is provided. The method comprises connecting an output side of an external cooling system to a return side of an electric motor driven pump (EMDP) in the hydraulic system and connecting an input side of the external cooling system to a hydraulic fluid reservoir in the hydraulic system. The EMDP pumps hydraulic fluid through the hydraulic system under conditions wherein fuel tanks in the aircraft are empty, and the external cooling system cools the hydraulic fluid as the EMDP pumps the hydraulic fluid, wherein the hydraulic fluid passes from the hydraulic fluid reservoir and through the external cooling system before entering the EMDP.