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tenance work on the airplane electrical system (with the exception of elec
tronic equipment).
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.
connected, a contactor automatically opens the circuit to
the electronic portion of the split bus bar as a protection
against damage to the transistors i n the electronic equip
ment by transient voltages from the power source.
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.
the ground service plug is correctly connected to the airplane.
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.
external power s ystem supplies the needed "jumper" across the contacts s o
that with a "dead" battery an d 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.
If erroneous instrument readings are suspected due to water or ice
in the static system ports or lines, the static pressure alternate s ource
valve knob should be pulled on, venting the static system to the cabin.
7-2
NGrE
When an external power source is
Power from the ex ternal power source will flow only if
There
A special fused circuit in the
If the plug
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