The test procedure applies to the refueling manifold system connecting the receiver aircraft fuel tanks to the refueling source fuel pump(s) for both ground and aerial refueling. The test procedure is intended to verify that the limit value for surge pressure specified for the receiver fuel system is not exceeded when refueling from a refueling source which meets the requirements of AS1284 (reference 2). This recommended practice is not directly applicable to surge pressure developed during operation of an aircraft fuel system, such as initiating or stopping engine fuel feed or fuel transfer within an aircraft, or the pressure surge produced when the fuel pumps are first started to fill an empty fuel manifold.

Purpose:

The need for large fuel loads requires high refueling rates for both ground and aerial refueling to minimize refueling time. Stopping the high refueling fuel velocity in a short period of time causes a pressure in the refueling system (both aircraft systems and refueling equipment) higher than the normal operating pressure. This higher pressure, called surge pressure, or water hammer, is described in reference 1, section 3.10, "Fluid Transients." The intensity of the surge pressure is dependent upon the interaction between the aircraft refueling system and the refueling source system. This document establishes a standard procedure for testing an aircraft refueling system when combined with a refueling source (refueling truck, hose cart, hydrant system, or aerial refueling tanker) to verify that the surge pressure within the receiver aircraft does not exceed the value specified for the system.