This SAE Aerospace Recommended Practice (ARP) provides a procedure for obtaining filter patch test samples from the following types of aerospace non-rotating hydraulic equipment: ? Mechanical/Hydraulic Units ? Electro/Hydraulic Units ? Pneumatic/Hydraulic Units Purpose This ARP provides the recommended practices to obtain and evaluate filter patch tests for aerospace hydraulic non-rotating equipment which are to be used in a quality control program to ensure that: ? The equipment meets cleanliness standards ? The equipment is not generating contaminants ? The equipment is 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 servo-valves and slide valves.