Figure 8-1.--Periodic fluid surveillance requirements.
is not taken, the complete system could be con-
MAINTENANCE PROCEDURES
taminated. Hydraulic systems and components are
The general contamination control procedures and
serviced by using approved fluid dispensing equipment
testing of hydraulic systems, subsystems, components,
only. Unfiltered hydraulic fluid should NEVER be
and fluids are requirements for each maintenance level.
introduced into systems or components.
Hydraulic fluid contamination controls ensure the
All portable hydraulic test stands must receive the
cleanliness and purity of fluid in the hydraulic system.
required periodic maintenance checks. Make certain
Fluid sampling and analysis is performed periodically.
that each unit is approved, and the applicable MIM is
Checks are made sufficiently before the scheduled
readily accessible and up to date. When the portable
aircraft induction date so that if fluid decontamination
hydraulic test stand is not in use, it should be protected
is required, it may be accomplished at that time. The
against contaminants such as dust and water. You
condition of the fluid depends, to a large degree, on the
should ensure that correct hoses are used on each stand,
condition of the components in the system. If a system
and that they are approved for the type of fluid being
requires frequent component replacement and
used. Properly cap hoses when they are not being used.
servicing, the condition of the fluid deteriorates
Hoses must be serialized and must remain with the
proportionately.
equipment. Make sure the hoses are coiled, kept free of
Replacement of aircraft hydraulic system filter
kinks, and properly stowed. Make sure they are in
elements takes place on a scheduled or conditional
satisfactory condition and are checked periodically.
basis, depending upon the requirements of the specific
Replace any hose that exhibits fluid seepage from the
system. A differential pressure flow check and bubble
outer cover or separation between the inner tube and the
point test are performed to properly evaluate the
outer cover. Portable hydraulic test stands that show
condition of a cleanable filter element. These two
indications of contamination or that have loaded
checks are done to verify that the element is good
(clogged) filters are removed from service im-
before it is installed in a system or component. Many
mediately and returned to the supporting activity for
filter elements look identical, but not all of them are
maintenance.
compatible with flow requirements of the system.
Use only approved lubricants for O-ring seals;
If the hydraulic system fluid is lost to the point that
incorrect lubricants will contaminate a system. Many
the hydraulic pumps run dry or cavitate, you should
lubricants look alike, but few are compatible with
change the defective pumps, check filter elements, and
hydraulic fluids. The only approved O-ring seal
decontaminate the system as required. Check the
lubricants are hydraulic fluid MIL-H-5606, hydraulic
applicable MIM for corrective action to be taken
fluid MIL-H-83282, hydraulic fluid MIL-H-46170, or
regarding decontamination of the system. If this action
a thin film of grease, MIL-G-81322.
8-3
