Vacuum System Filter - Cessna 1969-1976 172 Series Service Manual

d. Re s u r e air box
is
clean, inspect filter and r e -
place if damaged.
NOTE
A damaged filter may have broken filtering
panels or the flock coating may b e missing
from the filtering panels, which will allow
unfiltered air to enter the induction system.
Any filter that appears doubtful, shall have
a new
filter installed in its place.
e. Install filter at entrance to air box with gasket
on aft face of filter frame and with air flow arrow on
filter pointed in the correct direction.
To service the d r y type filter, proceed
as follows:
a. Remove filter from aircraft.
NOTE
U s e c a r e to prevent damage to filter element
when cleaning filter with compressed air.
b. Clean filter by blowing with compressed air
(not over 100 psi) from direction opposite of normal
air flow. Arrows on filter case indicate direction of
normal air flow.
Do not use solvent o r cleaning fluids to wash
filter. Use only a water and household deter-
gent solution when washing the filter.
c. After cleaning as outlined in step "b, the filter
may be washed,
if
necessary, in
a solution of warm
water and
a mild household detergent. A cold water
solution may be used.
NOTE
The filter assembly may be cleaned with
compressed air
a maximum of 30 times o r
it may be washed a maximum of 20 times.
A new filter should be installed after using
500 hours of engine operating time o r one
year, whichever should occur first. How-
ever, a new filter should be installed at
anytime the existing filter is damaged. A
damaged filter may have sharp o r broken
edges in the filtering panels which would
allow unfiltered air t o enter the induction
system. Any filter that appears doubtful,
shall have a new filter installed in its place.
d. After washing, rinse filter with clear water un-
til rinse water draining from filter is clear. Allow
water to drain from filter and dry with compressed
air (not over 100 psi.
NOTE
The filtering panels of the filter may become
distorted when wet, but they will return to
their original shape when dry.
e. Be s u r e air box is clean, inspect filter.
If
filter is damaged, install a new filter.
f . Install filter
at entrance to air box with gasket
on aft face of filter frame and with air flow arrows
on filter frame pointed in the correct direction.
2-23. VACUUM SYSTEM FILTER. The vacuum sys-
tem central air filter keeps d i r t and dust from enter-
ing the vacuum operated instruments. Chan e central
air filter element every 500 hours of o p e r a t i b time
and whenever suction gage reading drops bel w 4.6
inches of mercury. Also, do not operate the vacuum
disconnected as particles of dust o r other foreign
matter may enter the system and damage the gyros.
2-24. BATTERY. B>@ery servicing involves add-
ing distilled water t o maintain the electrolyte even
with the horizontal baffle plate at the bottom of the
filler holes, checking the battery cable connections,
and neutralizing and cleaning off and spilled electro-
lyte or corrosion. Use bicarbonate of soda (baking
soda) and water to neutralize electrolyte or corro-
sion. Follow with
.a thorough flushing with water.
Brighten cables and terminals with
a wire brush,
then coat with petroleum jelly before connecting.
The battery box also should be checked and cleaned
if
any corrosion is noted. Distilled water, not acid
o r "rejuvenators,
t t
should be used to maintain elec-
trolyte level. Check the battery every 50 hours (or
at
least every 30 days) oftener in hot weather. See
Section 16 for detailed battery removal, installation
and testing.
2-25. TIRES. Maintain t i r e pressure
at the air
pressures specified in figure 1-1. When checking
tire pressure, examine tires for wear, cuts, bruises,
and slippage. Remove oil, grease, and mud from
tires with soap and water.
system with the filter removed, o r a vacuum
1
ine
%
NOTE
Recommended t i r e pressures should be main-
tained. Especially in cold weather, remember
that any drop in temperature of the air inside
a t i r e causes a corresponding drop in air pres-
sure.
2-26. NOSE GEAR SHOCK STRUT. The nose gear
shock strut requires periodic checking t o ensure
that the strut is filled with hydraulic fluid and is
inflated to the correct
air
pressure. To service the
nose gear shock strut, proceed
as follows:
a. Remove valve cap and release air pressure.
b. Remove valve housing.
c. Compress nose gear to
its
shortest length and
fill
strut with hydraulic fluid to the bottom of the
filler hole.
d. Raise nose of aircraft, extend and compress
s t r u t several times t o expel any entrapped air, then
lower nose of aircraft and repeat step "c.
e. With strut compressed, install valve housing
assembly.
f . With nose wheel off ground, inflate strut. Shock
strut pressure
is
listed in Section 1.
2-9