Beechcraft C-12C Operator And Technical Reference Manual page 123

GENERATOR T2 , are located on the overhead
control panel under the MASTER SWITCH.
toggle switches control electrical power from the
designated generator to paralleling circuits and the bus
distribution system. Switch positions are RESET / ON
/ 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 GEN / GENERATOR switch
in the OFF position, the affected unit cannot have its
output restored to aircraft use until the GEN /
GENERATOR switch is moved to RESET, then ON.
d. Master Switch. All electrical current may be
shut off using the MASTER SWITCH bar that extends
above the battery and generator switches.
MASTER SWITCH bar is moved forward when a
battery or generator switch is turned on. When moved
aft, the bar forces each switch to the OFF position.
e. Volt-Loadmeters
the overhead control panel display voltage readings
and show the rate of current usage from left and right
generating systems. Each meter is equipped with a
spring-loaded push-button
manually pressed, will cause the meter to indicate
main bus voltage. Each meter normally shows output
amperage reading from the respective generator,
unless the push-button switch is pressed to obtain bus
voltage reading. Current consumption is indicated as
a percentage of total output amperage capacity for the
generating system monitored.
f. DC Load and Voltmeters
meters, located on the overhead panel, display voltage
readings and show the rate of current usage from the
left and right generating systems.
meters indicate output amperage as a percent of rated
capacity from the respective generator.
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.
g. Battery Monitor.
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 yellow BATTERY CHARGE annunciator
light and the master fault caution light will illuminate.
Following a battery engine start, the caution light will
illuminate approximately 6 seconds after the generator
switch is placed in the ON position.
normally extinguish within 2 to 5 minutes, indicating
The
The
C D T1. Two meters on
switch which, when
T2 . Four digital
The two load
Current
Nickel-cadmium battery
The light will
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).
illuminate for short intervals after landing gear and/or
flap operation. If the caution light should illuminate
during normal steady-state cruise, it indicates that
conditions exist that may cause a battery thermal
runaway. If this occurs, the battery switch shall be
turned OFF and may be turned back ON only for gear
and flap extension and approach to landing. Battery
may be usable after a 15 to 20 minute cooldown
period.
h. Battery Temperature Monitoring System
T2 . A battery temperature indicator system is
provided to monitor the temperature of the nickel
cadmium battery. The system consists of a battery
temperature probe, a dc-powered (ANVIS) post lighted
indicator, push-to-test switch and system circuit
breaker. The battery temperature indicator and push-
to-test switch, placarded BAT TEMP TEST, are both
located on the pilot's subpanel. The systems circuit
breaker, placarded BATT TEMP, is located in the
WARNING section of the overhead circuit breaker
panel. Dimming of the post lighted instrument is
provided through the SUBPANEL LIGHTS rheostat.
The instrument indicating range is 100 °F
(bottom of scale), to 190 °F (top of scale). A red,
yellow and green band located alongside the indicator
scale and two annunciators (lower) caution and
(upper) warning located on the face of the indicator
provide visual battery temperature information. When
illuminated, the lower annunciator indicates the battery
temperature exceeds 120 °F, the upper annunciator
indicates the battery temperature exceeds 150 °F.
The push-to-test switch, placarded BAT TEMP
TEST, when pressed and held, will normally move the
indicator pointer to the top of the scale and illuminate
both annunciators. The pointer rate of rise will vary,
being somewhat slower
temperatures. If a probe is faulty or leaking, or a wire
is broken, the pointer may not move at all or may stop
down the scale. Allow approximately 45 seconds for
the pointer to move to the top of the scale in normal
temperatures; 60 seconds in colder temperatures.
i. Generator Out Warning Lights.
caution/advisory annunciator panel lights inform the
pilot when either generator is not delivering current to
the aircraft dc bus system. These lights are placarded
#1 DC GEN and #2 DC GEN. Two flashing MASTER
CAUTION lights and illumination of either fault light
indicates that either the identified generator has failed
TM 1-1510-218-10
The caution light may also
with colder battery
Two
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