The purpose of this document is to provide guide lines for allowable leakage for in-service aircraft hydraulic components at a nominal 100 F temperature and to outline the procedure for measuring such leakage. The limits to be applied to any specific aircraft should be adjusted before inclusion in a maintenance manual. Leakage as hereafter referred to in this document shall mean external leakage. The allowable leakage for hydraulic components has been documented in various military specifications concerning components. The leakage requirements given in the military specifications are intended in part to control the quality, assembly and proper functioning of the components. However, components that are in service sometimes develop leakage rates in excess of the specified amount. The does not necessarily imply that the components have degraded to a degree that they no longer provide reliable operation or that they would be detrimental to the system. The intent of this ARP is to establish a level of allowable leakage that will be applicable only to in-service hydraulic components. It is hoped that this will result in minimizing what is often the unnecessary removal of hydraulic components from an aircraft.