GROUND
SERVICE
PLUG
RECEPTACLE.
A
ground
service
plug
receptacle
may
be
installed
to
permit
use
of
an
external
power
source for
cold
weather starting
and during lengthy
main-
tenance work
on
the
airplane electrical system
(with
the exception
of
elec-
tronic
equipment).
NOTE
Electrical
power for the
airplane electrical circuits is pro-
vided through a
split
bus
bar
having
all electronic circuits
on
one
side
of
the bus and other
electrical circuits
on
the
other
side
of
the bus. When
an external
power
source is
connected, a
contactor automatically
opens the
circuit
to
the
electronic
portion
of
the
split
bus
bar as a protection
against
damage
to
the
transistors
in the
electronic
equip-
ment
by
transient voltages from
the power
source. There-
fore,
the
external
power
source
can not
be
used as
a
source
of
power
when
checking
electronic
components.
Just
before connecting an
external
power
source (generator
type or
bat-
tery cart),
the
master
switch should
be
turned
"ON."
.
The ground
service
plug
receptacle circuit incorporates a polarity
re-
versal protection.
Power from the
external
power source will flow
only if
the ground
service
plug
is correctly
connected to the
airplane.
If
the plug
is accidentally
connected backwards,
no
power will
flow
to the
airplane's
electrical system, thereby
preventing
any
damage
to
electrical
equipment.
The
battery
and
external
power
circuits
have been designed to com-
pletely eliminate
the need
to
"jumper' across
the
battery
contactor to close
it for
charging
a
completely
"dead
battery.
A
special
fused
circuit
in
the
external
power
system
supplies the needed
"jumper" across
the contacts so
that with a '"dead"
battery
and an
external
power
source
applied, turning
the
master
switch
"ON"
will close the
battery contactor.
STATIC
PRESSURE
ALTERNATE
SOURCE VALVE.
A
static pressure alternate source
valve
is
available to provide con-
tinued
operation
of
the
airspeed indicator, altimeter
and
vertical
speed
indicator
in the event
that
the
static system ports
or
lines
become ob-
structed.
7-2
Summary of Contents for 182 1973
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