TM 55-1510-220-10
hold the switch at the INCR position, to decrease cabin
temperature, hold the switch in the DECR position.
Allow approximately 30 seconds per valve to drive the
bypass valves to the fully open or fully closed position.
Only one valve moves at a time.
(2)
With the cabin temperature selector
switch in the MAN COOI, position, the automatic
temperature control system is bypassed. In the manual
cooling mode, the refrigeration system is on, providing
the right engine NI speed is above 65'SY, however, the
bypass valves may be manually positioned for the
desired temperature. Hold the MANUAL TEMP switch
in the DECR position approximately one minute to fully
close air-to-air heat exchanger bypass valves.
e.
Bleed Air and Vent Control.
(1)
Bleed air entering the cabin is controlled
by bleed air valve switches placarded BLEED AIR
VALVE OPEN ENVIRO OFF PNEU & ENVIRO OFF.
When the switch is in the OPEN position, the
environmental flow control unit and the pneumatic valve
are open. When the switch is in the ENVIRO OFF
position, the environmental flow control unit is closed
and
the pneumatic bleed air valve is open; in the PNEU &
ENVIRO OFF position, both are closed. For maximum
cooling on the ground, turn the bleed air valve switches
to the ENVIRO OFF position.
(2)
The forward vent blower is controlled by a
switch placarded VENT BLOWER AUTO LOW HI. The
HI and LOW positions regulate the blower to two speeds
of operation. IN the AUTO position, the fan will run at
low speed except when the CABIN TEMP mode selector
switch is placed in the OFF position. In the OFF
position, the blower will not operate.
(3)
Aft vent blower switch. The aft vent
blower is controlled by a switch placarded AFT VENT
BLOWER OFF AUTO ON, located on the overhead
control panel (fig. 2-12). The single speed blower
operates automatically through the cabin temperature
mode selector switch when the aft vent blower switch is
placed in the AUTO position during ground operation
and the air conditioner is operating. The blower runs
continuously when the switch is placed in the ON
position. In the OFF position, the blower will not
operate.
Section IX. ELECTRICAL POWER SUPPLY AND DISTRIBUTION SYSTEM
2-72. DESCRIPTION.
The aircraft employs both direct current (DC) and
alternating current (AC) electrical power. The DC
electrical power supply (fig. 2-23) is the basic power
system energizing most aircraft circuits. Electrical
power is used to start the engines, to power the landing
gear and flap motors, and to operate the standby fuel
pumps,
ventilation
blower,
lights
and
electronic
equipment. AC power is obtained from DC power
through inverters. The single phase AC power system is
shown in figure 2-24, and the three phase AC power
system is shown in figure 2-25. The three sources of
DC power consist of one 20 cell 34-ampere/hour battery
and two 400-ampere starter-generators. DC power may
be applied to the aircraft through an external power
receptacle on the right nacelle (refer to Section XII for
GPU
requirements).
The
3tarter-generators
are
controlled by generator control units. The output of
each generator passes / through a cable to the
respective generator bus (fig. 2-23). Other buses
distribute power to aircraft DC loads, and derive power
from the generator buses. The generators are
paralleled to balance the DC loads between the two
units. When one of the generating systems is not on
line, if no fault
exists, aircraft DC power requirements continue to be
supplied from one or the other generating source, but
not from both. Most DC distribution buses are
connected to both generator buses but have isolation
diodes to prevent power crossfeed between the
generating systems, when connection between the
generator buses is lost. Thus, when either generator is
lost because of a ground fault, the operating generator
will supply power for all aircraft DC loads except those
receiving power from the inoperative generator's bus
which cannot be crossfed. When a generator is not
operating, reverse current and over-voltage protection is
automatically provided. Two inverters operating from
DC power produce the required single-phase AC power.
Three phase AC electrical power for inertial navigation
system and mission avionics is supplied by two DC
powered mission inverters. AC power may be applied
through an external power receptacle located on the left
nacelle. The mission power system is shown in figure 2-
26.
2-73. DC POWER SUPPLY.
One nickel-cadmium battery furnishes DC power
when the engines are not operating. This
Change 2 2-59