Depressurize reservoir (if necessary).
4 Unscrew the filter case and remove it from the filter head, using a slight rocking and downward pull on the
case after the case threads are free from the filter.
5 Extract the retaining ring and remove the filter element from the cases.
6 After ensuring that a replacement filter element is available, cut the filter element.
7.Before Installing the new filter, clean the filter head and the filter case and inspect them for damage;
replace all damaged parts.
Replace all O-ring packings
Fill the filter bowl with new fluid before attaching it to the filter housing head. Filling the bowls helps to
stop the Injection of air into the system
10 Install the filter in its case and screw the case into the filter head. The correct torque is usually handtight
plus one-eighth of a turn, but always check the specific maintenance manual for the specific torque value.
11. Pressurize the hydraulic system and inspect the filter assembly for leaks. If the assembly is
Satisfactory, replace the lockwire between the filter case and the head assembly.
(2) Stainless steel elements. Stainless steel filter elements are used in most modern aircraft. Filter element
surfaces of this type usually have a corrugated stainless steel mesh construction. Such filters are usually rated from 5to
10-micron nominal flow and at 25micron absolute flow. This means about 95 percent of 5to 10-micron particles and 100
percent of 25-micron particles will be filtered from the fluid. The curved passages of the filter element limit the length of
the particles that pass through the filter.
Drycleaning solvent is flammable and solvent vapors are toxic. Use P-D-680, Type II Solvent in a well-
ventilated area Keep away from open flames. Avoid prolonged solvent contact with skin.
Under no condition shall a wire brush be used in cleaning filter element. Failure to comply will result in
possible failure of equipment.
The use of any alcohol in cleaning components which contact hydraulic fluids is prohibited Formation of a
polymeric residue can result which could impair mechanical operation of the component.
(a) Wash filter element In drycleaning solvent, Federal Specification P-D-680, using a soft lint-free cloth
Allow to drain, and dry with low pressure compressed air
(b) Replace filter element when cracks, tears, and other signs of deterioration are noted.
d. Two-Stage Fluid Filters. Two-stage line-type hydraulic system filters are being used in some recent
aircraft models The typical two-stage filter has two filter elements, two bypass valves, and two differential pressure
indicators The first-stage element can filter out smaller particles than the second-stage element can. Normally, the fluid
passes through both elements, flowing first through the first stage element. As long as the first stage element is
unclogged and functioning, there will be no foreign matter left for the second-stage element to remove. However, if the
first-stage element becomes clogged, its bypass valve opens and fluid goes directly from the filter inlet port to the
second-stage element, which then takes over the job of filtering out foreign particles Although the second-stage element
is not capable of filtering out the very small particles, it can be safely used until the first-stage element is unclogged.