TM 55-1510-215-10
The toggle switches control electrical power from the
may also illuminate for short intervals after landing gear
designated generator to paralleling circuits and the bus
and/or flap operation.
If the caution light should
distribution system. Switch positions RESET, ON and
illuminate during normal steady-state cruise, it indicates
OFF are placarded on the MASTER SWITCH. RESET
that conditions exist that may cause a battery thermal
is up (spring-loaded back to ON), ON is center, and OFF
runaway. If this occurs, the battery switch shall be
is down. When a generator is removed from the aircraft
turned OFF and may be turned OFF and may be turned
electrical system, due either to fault or from placing the
back ON only for gear and flap extension and approach
GEN switch in the OFF position, the affected unit cannot
to landing.
have its output restored to aircraft use until the GEN
switch is moved to RESET, then ON.
NOTE
c. Master Switch. All electrical current may be shut
Battery may be usable after a 15 to 20
off using the MASTER SWITCH bar (fig. 2-7) which
minute cool down period.
extends above the battery and generator switches. The
MASTER SWITCH bar is raised when a battery or
f. Generator Out Warning Lights. Two annunciator
generator switch is turned on. Placed down, the bar
panel fault lights inform the pilot when either generator is
forces each switch to the OFF position.
not delivering current to the aircraft DC bus system.
These lights are placarded L GEN OUT and R GEN
d. Volt-Loadmeters .
Two meters on the left
OUT (fig. 2-22). Two flashing MASTER WARNING
subpanel display voltage readings and show the
lights and illumination of either fault light indicates that
electrical load from left and fight generating systems
either the identified generator has failed or voltage is
insufficient to keep it connected to the bus distribution
push-button switch which when manually pressed will
system.
cause the meter to indicate main bus voltage. Each
member normally shows output electrical lad from the
g. DC External Power Source. External DC power
respective generator, unless the push-button switch is
can be applied to the aircraft through an external power
pressed to obtain bus voltage reading.
Current
receptacle on the underside of the right wing leading
consumption is indicated as a percentage of total output
edge just outboard of the engine nacelle (fig. 2-23). The
amperage capscrew for the generating system
receptacle is installed inside of the wing structure and is
monitored.
accessible through a hinged access panel. DC power is
supplied through the DC external plug and applied
e. Battery Monitor.
Nickel-cadmium battery
directly to the battery bus after passing through the
overheating will cause the battery charge current to
external power relay. The holding coil circuit of the relay
increase. The aircraft has a charge-current sensor
is energized by the external power source. The BAT
which will detect a charge current. The charge current
switch must be in the ON position to connect external
system senses battery current through a shunt in the
DC power to the aircraft circuits.
negative lead of the battery. Any time the battery
charging current exceeds approximately 7-amperes for 6
2-70. AC Power Supply.
seconds or longer the yellow BATTERY CHARGE
annunciator light, if installed, and the master fault
AC power for the aircraft is supplied by two inverters,
caution light will illuminate. Following a battery engine
which obtain operating current from the DC power
start, the caution light will illuminate approximately six
system.
The inverters are operated by a switch
seconds after the generator switch is placed in the ON
placarded AIRCRAFT INVERTER 1 OFF 2, located on
position. The light will normally extinguish within two to
the pilot's subpanel. Only one inverter can be operated
five minutes, indicating that the battery is approaching a
at a time. The second inverter remains as a spare to be
full charge. The time interval will increase if the battery
used in case of AC power failure. The single-phase
has a low state of charge, the battery temperature is
inverters provide 115 VAC power to the vertical and
very low, or if the battery has previously been
directional gyros. The inverters also provide 26 VAC
discharged at a very low rate (i.e., battery operation of
power to the following engine instruments: fuel flow, oil
radios or lights for prolonged periods). The caution light
pressure, torquemeter; and avionics systems: HDG,
RMI, compass. ADI, yaw damp.
2-62 Change 10
