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CHECK
VALVE
CHECK VALVE
VACUUM
VACUUM
REGULATOR
REGULATOR
GYRO
DIRECTIONAL
HORIZON
GYRO
CENTRAL
AIR FILTER
(TD-671
AND AFTER)
L.H.
VACUUM
PUMP
(TD
6A
UhrM GM-
07)
R.H.
VACUUM PUMP
Figure
3-17.
Vacuum
System
and
Central
Air Filter
ADJUSTING
THE
PRESSURE
SYSTEM
(TD-708
ments
may be accomplished
without
removing
the
and after)
instrument
from
the
airplane.
The frequency
of
cleaning
or replacing
the
air filters
will depend
a.
Start
only one engine
and set
the throttle to
upon
service
conditions;
however,
they
should
be
obtain
2200 rpm.
checked
approximately
every
100 hours
of operation.
It should
be
borne
in mind when operating
in local-
b.
Adjust
the
pressure
regulator
in
the
appropri-
ities where
there
is
an
excessive
amount
of sand
or
ate nacelle
to
obtain
a
gage reading
of
3.5
to
4.5
dust in
the
air,
that the
filter
should
be inspected,
pressure.
Shut down
engine.
and
if necessary,
replaced
at
more
frequent
inter-
Vals.
Under
extremely
dusty
conditions,
it may be
c.
Repeat
steps
a and b with
the
opposite
engine.
necessary
to
inspect
the
filter
daily.
A
clogged
filter
reduces
air
flow and
slows
up
the
rotor,
d.
After
both regulators
have
been individually
causing
a
loss
of gyroscopic
inertia
and improper
adjusted,
start
both engines
and set
the
throttles
at
gyro indication.
2200
rpm.
The pressure
gage
should
read
between
3.
5
to
4. 5
.
To replace
the filter assembly
on
the
instrument,
remove
the
air
filter
body-cover
by
taking
out the
four
fillister-head
machine
screws.
Lift out
the
CLEANING
THE
SUCTION
RELIEF
VALVE
snap ring which
holds the
filter
in place,
remove
SCRE EN
the
filter,
and
replace
it with a new one.
Replace
the
air
filter
body-cover
and gasket,
securing
them
How often
the
screens
are cleaned
depends
on
the
with
screws.
If
the
air filter
body-cover
is not used,
conditions
under
which
the
airplane
is
flown.
Should
the
filter
may be removed
by lifting
the
snap
ring
the
valves
need adjusting,
especially
to
lower
the
past
the
four protective
lugs.
vacuum,
the
screen
should be cleaned
and
the
setting
rechecked
before
readjusting.
The
screen
should
be
Aircraft
serials
TD-671
thru
TD-707
have
a
central
washed
in Stoddard
solvent,
or
a
similar
cleaner,
air
filter
installed
behind
the
instrument
panel.
The
then
blown
dry
with high pressure
air.
filter
(two
filters
are
used
with dual
instruments),
should
be replaced
every
500
hours
or less
if oper-
ating in
heavy
smoke
or
dust conditions.
Aircraft
REPLACING
GYRO
INSTRUMENT
AIR FILTERS
TD-708
and after
have an air filter
located
in
each
nacelle.
This
filter
should
be
replaced
every
500
The replacement
of
the
air filter
in
the
gyro instru-
hours
as noted above.
An
additional
air filter
is
3-31
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