This document sets forth recommendations of SAE Subcommittee A-6B (Fluid Power Sources) relative to the procedure and methods to be used in the obtaining and evaluation of filter patch tests for aerospace hydraulic non-rotating equipment. These patches are to be used in a quality control program to insure that the units meet cleanliness standards, are not generating contaminant, and the units are operating properly prior to delivery to the customer. This is to promote an improvement in cleanliness standards in aerospace hydraulic circuits. It is expected that this will promote a longer service life in non-rotating hydraulic equipment such as electrohydraulic servovalves and slide valves. (Reference: ARP 575 is a similar document used for testing of pumps and motors.)