Textron Cessna 172R - Master Switch

CESSNA
MODEL
172R
SECTION
7
AIRPLANE
&
SYSTEMS
DESCRIPTION
MASTER
SWITCH
The
master
switch
is
a
split
rocker
type
switch labeled
MASTER,
and is
ON
in
the
up
position
and
OFF
in
the
down
position.
The|
right
half of
the
switch,
labeled
BAT,
controls all
electrical
power
to
the
airplane.
The
left
half,
labeled
ALT,
controls
the
alternator.
A
CAUTION
PRIOR
TO TURNING
THE
MASTER SWITCH
ON
OR
OFF,
STARTING
THE
ENGINE
OR
APPLYING
AN EXTERNAL
POWER
SOURCE,
THE
AVIONICS
MASTER SWITCH
SHOULD
BE
TURNED
OFF
TO
PREVENT ANY
HARMFUL
TRANSIENT
VOLTAGE
FROM DAMAGING
THE
AVIONICS
EQUIPMENT.
I
\
Normally,
both sides
of
the
master
switch should be used
simultaneously;
however,
the
BAT
side
of
the
switch could be
turned
on
separately
to
check
equipment
while
on
the
ground.
To check
or
use
avionics
equipment
or
radios
while
on
the
ground,
the
avionics
master
switch
must
also
be
turned
on.
The
ALT
side
of
the
switch,
when
placed
in
the
OFF
position,
removes
the
alternator
from
thel
electrical
system.
With
this
switch
in
the
OFF
position,
the
entirel
electrical
load
is
placed
on
the
battery.
Continued
operation
with
the
alternator
switch
in
the
OFF
position
will
reduce
battery
power
low|
enough
to
open
the
battery
contactor,
remove
power
from
the
alternator
field,
and
prevent
alternator
restart.
Revision
8
7-33
All manuals and user guides at all-guides.com