Textron Cessna 172R User Manual

CESSNA
MODEL
172R
SECTION
7
AIRPLANE
&
SYSTEMS DESCRIPTION
VACUUM
GAGE
|
The
vacuum
gage
is
part
of
the
ammeter/vacuum
gage,
located|
on
the
lower
left
corner
of
the
instrument
panel.
It
is calibrated
in
inches
of
mercury
and indicates
vacuum
air available
for
operation
of
the
attitude
and
directional indicators.
The
desired
vacuum
range
is
4.5
to
5.5
inches
of
mercury.
Normally,
a
vacuum
reading
out
of
this
range may
indicate
a
system
malfunction
or
improper
adjustment,
and
in
this
case,
the attitude
and
directional
(heading)l
indicators should
not
be
considered reliable.
However,
due
to
lower
atmospheric
pressures
at
higher
altitudes,
the
vacuum
gage
may|
indicate
as
low
as
4.0
in.
Hg.
at
20,000
feet
and still be
adequate
for
normal
system
operation.
LOW VACUUM
ANNUNCIATION
Each
engine-driven
vacuum
pump
is
plumbed
to
a common
manifold,
located
forward of
the
firewall.
From
the
tee,
a
single
line
runs
into
the
cabin
to
operate
the
various
vacuum
system
instruments.
This
tee
contains check valves
to
prevent
back
flow
into
a
pump
if
it
fails.
Transducers
are
located
just
upstream
of
the
tee
and
measure
vacuum
output
of
each
pump.
If
output
of
the
left
pump
falls
below
3.0
in.
Hg.,
the amber
L
VAC
message
will
flash
on
the
annunciator
panel
for
approximately
10
seconds
before
turning steady
on.
If
output
of
the
right
pump
falls
below
3.0
in.
Hg.,
the amber
VAC
R
message
will
flash
on
the
annunciator
panel
for
approximately
10
seconds
before
turning
steady
on.
If
output
of
both
pumps
falls
below
3.0
in.
Hg.,
the amber
L
VAC
R
message
will
flash
on
the annunciator
panel
for
approximately
10
seconds
before
turning
steady
on.
Revision
8
7-45
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Textron Cessna 172R Specifications

General

Brand	Textron
Model	Cessna 172R
Category	Aircrafts
Language	English