MAINTENANCE PROCEDURES

accomplished at all levels of maintenance through the use of Contamination Analysis Kit 57L414. Hydraulic system fluid sampling is accomplished on a periodic basis according to the applicable maintenance instruction manual (MIM), maintenance requirement cards (MRC), and rework specification. Figure 4-1 shows the requirements for periodic fluid surveillance. You should perform analysis of hydraulic systems if extensive maintenance and/or crash/battle damage occurs. You should perform the analysis when a metal-generating component fails, an erratic flight control function or a hydraulic pressure drop is noted, or there are repeated and/or extensive system malfunctions. Analysis is performed when there is a loss of system fluid, or when the system is subjected to excessive temperature. Analysis is also performed when an aircraft is removed from storage in accordance with NAVAIR 15-05-500. You should perform analysis of the hydraulic system anytime hydraulic contamination is suspected. MAINTENANCE PROCEDURES The general contamination control procedures hydraulic systems, subsytems, components, and fluids are requirements for each maintenance level. Hydraulic fluid contamination controls ensure the cleanliness and purity of fluid in the hydraulic system. Fluid sampling and analysis is performed periodically. Checks are made sufficiently before the scheduled aircraft induction date so that if fluid decontamination is required, it may be accomplished at that time. The condition of the fluid depends, to a large degree, on the condition of the components in the system. If a system requires frequent component replacement and servicing, the condition of the fluid deteriorates proportionately. Replacement of aircraft hydraulic system filter elements takes place on a scheduled or conditional basis, depending upon the requirements of the specific system. A differential pressure flow check and bubble point test are performed to properly evaluate the condition of a cleanable filter element. These two checks are done to verify that the element is good before it is installed in a system or component. Many filter elements look identical, but all of them are not compatible with flow requirements of the system. If the hydraulic system fluid is lost to the point that the hydraulic pumps run dry or cavitate, you Figure 4-1.—Periodic fluid surveillance requirements. 4-2 and testing of