to enter aircraft circuits. When the MASTER SWITCH
(gangbar) is placed down, the BATTERY switch is
removed from the aircraft electrical
system, due to fault, power cannot be
restored to the system until the
OFF/RESET, then ON.
Generator Switches. The two switches
GENERATOR are located in the overhead control
panel. The toggle switches control electrical power from
the designated generator to paralleling circuits and the
bus distribution system. Switch positions are placarded
RESET, ON and OFF. RESET is forward (spring-
loaded back to ON), ON is center, and OFF is aft.
When a generator is removed from the aircraft electrical
system, due either to fault or from placing the
GENERATOR switch in the OFF position, the affected
unit cannot have its output restored to aircraft use until
the GENERATOR switch is moved to RESET, then ON.
Master Switch. All electrical current
may be shut off using the MASTER SWITCH gangbar
(fig 2-13) which extends above the battery and
generator switches. The MASTER SWITCH (gangbar)
is moved forward when a battery or generator switch is
turned on. When moved aft, the bar positions each
switch to the OFF position.
DC Load and Voltmeters. Four digital
meters, located in the overhead panel, display voltage
readings and show the rate of current usage from the
left and right generating systems. The two load meters
indicate output amperage as a percent of rated capacity
from the respective generator. Current consumption is
indicated as a percentage of total output amperage
capacity for the generating system being monitored.
The two voltmeters indicate bus voltage for the
respective generating system.
Battery Volt/Amp Meter. The mission
control panel (fig. 4-1), located in the fuselage sidewall
adjacent to the copilot's seat, incorporates a digital volt/
amp meter that displays available battery voltage, and
amperage. Minimum battery voltage for engine starting
is 22 VDC.
cadmium battery overheating will cause the battery
charge current to increase if thermal runaway is
imminent. The aircraft has a charge-current sensor
which will detect a charge current. The charge current
system senses battery current through a shunt in the
negative lead of the battery. Any time the battery
charging current exceeds approximately 7-amperes for
6 seconds or longer, the amber BATTERY CHARGE
annunciator and the master fault caution annunciator will
illuminate. Following a battery engine start, the caution
annunciator will illuminate approximately six seconds
after the generator switch is placed in the ON position.
The annunciator will normally extinguish within two to
five minutes, indicating that the battery is approaching a
full charge. The time interval will increase if the battery
has a low state of charge, the battery temperature is
very low, or if the battery has previously been
discharged at a very low rate (i.e., battery operation of
radios or lights for prolonged periods). The caution
annunciator may also illuminate for short intervals after
landing gear and/or flap operation. If the caution
annunciator should illuminate during normal steady-
state cruise, this indicates that conditions exist that may
cause a battery thermal runaway. If this occurs, the
battery current should be monitored using the battery
ammeter. If battery current continues to increase, the
battery is in thermal runaway and should be selected off
until the beginning of the approach.
Generator Out Warning Annunciators.
annunciators inform the pilot when either generator is
not delivering current to the aircraft DC bus system.
These annunciators are placarded #1 DC GEN and #2
DC GEN. Illumination of the two MASTER CAUTION
annunciators and either fault annunciator indicates that
either the identified generator has failed or voltage is not
sufficient to keep it connected to the power distribution
The GPU shall be adjusted to regulate
at 28 volts maximum to prevent
damage to the aircraft systems.
DC External Power Source. See figure
2-32. External DC power can be applied to the aircraft
through an external power receptacle on the underside
of the right wing stub, just outboard of the engine
nacelle. The receptacle is installed inside of the wing
structure and is accessible through a hinged access
panel. DC power is supplied through the DC external
power plug, through the external power