ROCKWELL
COMMANDER
112/B/TC/TCA
MAINTENANCE
MANUAL
SECTION
vm
INSTRUMENTS
AN
Am
BULB SIMILAR TO THAT ILLUSTRATED
MAY
BE OBTAINED LOCALLY FROM A SURGICAL
SUPPLY COMPANY.
THIS
IS
THE
TYPE
USED
IN MEASURING BLOOD PRESSURE.
PRESSURE
•
.
~--
THICK-WALL
~CLAMP
SURGICAL
HOSE
PRESSURE
BLEED-OFF
SCREW
~~
" AIR BULB WITH
CHECK VALVES
<:J
""CLAMP
SUCTION
00
NOT
APPLY
POSITIVE PRESSURE WITH THE AIRSPEED
AND
VERTICAL SPEED INDICATOR. CONNECTED TO THE
STATIC SYSTEM OR
DAMAGE
WILL RESULT.
X282
Figure
8-3.
Pitot-Static Test Bulb
monitors
the
system
for
indication of
correct
suction
pressure.
The
gage
indicates
difference
in
suction
before
and
after
air
passes
through a gyro.
This
differential
pressure
will
gradually
decrease
as
the
central
filter
becomes
dirty,
causing
a
lower
reading
on the
suction
gage.
The
various
components of the
vacuum
system
are
secured
by conventional
clamps,
mounting
screws
and
nuts.
When
removing
a compo-
nent,
remove
the mounting
screws
and
disconnect
the
inlet
and
discharge
lines.
When
installing
a vacuum
system
component, make
sure
connections
are
made
correctly.
Use
thread
lubricant
sparingly
and only on
male
threads.
Avoid
overtightening
connections.
Be-
fore
reinstalling
a
vacuum
pump,
coat
the pump
drive
splines
lightly with a high
temperature
grease
such
as
Dow Silicone
Number
30 (Dow-Corning
Co.,
Midland,
Mich. ).
VACUUM
REGULATOR VALVE. A vacuum
regulator
valve
is
installed
in
the
line
between the
instruments
and
the
pump. Since the pump
is
capable
of
creating
more
vacuum than needed, the
regulator
valve
varies
the
degree
of vacuum
placed
on
the
instrument
system
as
well
as
protecting
the
system
from
too much vacuum.
The
regulator
valve opens
to
admit
air
to
the
vacuum
pump
line
when the
desired
degree
of vacuum
is
attain-
ed.
VACUUM
FILTER.
A
dry-element
type vacuum
sys-
tem
filter
cartridge
protects
the
vacuum-driven
gyro
instruments
from
dust
and
other
impurities.
The
filter
element
should
be
changed
every
500
hours
or
sooner
if
the
suction
gage
reading
drops
below 4. 5
inches
of
mercury.
Cleaning
The
vacuum
system
regulator
valve
is
adjusted
to
maintain
4.5
to
5.2
inches
Hg.
as
indicated
on
the
suction
gage
and
cannot function
properly
if
the
air
filters
are
dirty.
The
dry-type
filter
cartridge
and
the
regulator
valve
filter
should
be
changed and the
system
cleaned
every
500
hours
or
sooner
if
the
sys-
tem
requires
it.
In
general,
low-pressure,
dry
com-
pressed
air
should
be
used
in
cleaning
the
system
components
removed
from
the
aircraft.
Components
that
are
exposed
to engine
oil
and
dirt
should
be
washed
with
Stoddard
solvent,
then
dried
with a
low-pressure
air
blast.
Check
hoses
for
collapsed
inner
liners
as
well
as
external
damage.
8-5
Copyright Commander Owners Group 2013 All Rights Reserved
**unofficial copy**
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