1. Vent blower operation - Check
2. VENT BLOWER switch - ON.
2. HTR switch - AUTO
3. Cold air outlets - Adjust as required.
3. CABIN TEMP control - As required.
4. CABIN AIR and VENT AIR controls -
Position as required.
4. CABIN AIR, DEFROST AIR control - As
c. Emergency Operation - Cabin Heat .
With the heater control switch off,
automatic temperature control should fail to operate, the
cold air will enter the cockpit and
temperature may be controlled manually by manipulating
cabin through the warm air outlets.
the HTR control switch between the OFF and MAN
d. Normal Operation - Ventilation System.
The two ventilation air blowers
1. HTR switch - OFF.
compartment only when the aircraft
is on the ground with landing gear
shock struts compressed by aircraft
Section IX. ELECTRICAL POWER SUPPLY AND DISTRIBUTION SYSTEM
When a generator is not operating, reverse current and
over-voltage protection is automatically provided. Two
This aircraft employs both direct current (DC) and
inverters operating from DC power produce the required
single-phase AC power.
The DC electrical supply forms the basic power
system, energizing most aircraft circuits.
2-69. DC Power Supply.
power is used to start the engines, to power the landing
gear and flap motors, and to operate the transfer and
One nickel-cadmium battery furnishes DC power when
auxiliary fuel pumps, heater blower, ventilation blower,
the engines are not operating. This is a 24-volt, 34-
lights and electronic equipment. AC power is obtained
ampere/hour battery, located in the right wing center
from Dc power through inverters. The three sources of
section, and accessible through a panel on the top of the
DC power consist of one 24 volt, 34 ampere/hour battery
wing. DC power is produced by two engine-driven 28-
and two 250 ampere starter-generators. The starter
volt 250-ampere starter-generators.
generators are controlled by generator control units.
indicators associated with the DC supply system are
The output of each generator passes through a cable to
located on the left subpanel, and consist of a single
the respective generator bus. Other busses distribute
battery switch (BAT), two generator switches (GEN 1
power to aircraft DC loads, and derive power from the
AND GEN 2), and single MASTER SWITCH and two
When the generator buses are
coupled, the generators may be paralleled to balance
SYSTEMS for battery vent system anti-icing.)
the Dc loads between the two units.
generating systems are not coupled, if no fault exists,
a. Battery Switch.
A switch, placard BAT, is
only generator paralleling and load balance between the
located on the left subpanel under the MASTER
two units is lost. In this circumstance, all aircraft DC
power requirements continue to be supplied, from one or
to the aircraft bus system through the battery relay, and
the other generator source, but not from both. Most DC
must be ON to allow external power to enter aircraft
distribution buses are connected to both generator
circuits. When the MASTER SWITCH is placed down,
buses but have isolation diodes to prevent power
the BAT switch is forced OFF.
crossfeed between the generator buses is uncoupled.
Thus, when either generator is lost because of a ground
b. Generator Switches . Two switches, placarded
fault, the operating generator will supply power for all
GEN 1 and GEN 2, are located on the left subpanel
aircraft DC loads except those receiving power from the
inoperative generator's bus which cannot be crossfed.
2-56 Change 10