Section I. GENERAL
3B-1. GENERAL DESCRIPTION.
This chapter covers the avionics equipment
configuration installed in C-12D2 aircraft. It includes a
brief description of the avionics equipment, its
technical characteristics, capabilities, and locations.
3B-2. AVIONICS EQUIPMENT CONFIGURATION.
The avionics configuration of the aircraft is
comprised of three groups of electronic equipment.
The communication equipment group consists of the
interphone, UHF command, VHF command, and HF
command systems. The navigation equipment group
provides the pilot and copilot with the instrumentation
required to establish and maintain an accurate flight
course and position and to make an approach on
Conditions (IMC). The navigation group includes
equipment for determining altitude, attitude, position,
destination, range and bearing, heading reference,
groundspeed, and drift angle. The transponder and
radar group includes identification, position, and
emergency tracking system and a radar system to
locate potentially dangerous weather areas. A Ground
Proximity Altitude Advisory System (GPAAS) is also
3B-3. POWER SOURCE.
a. DC Power. DC power for the avionics
equipment is provided by four sources: the aircraft
battery, the left and right generators, and external
power. Power is routed through two 50-ampere circuit
breakers to the avionics power relay that is controlled
by the AVIONICS MASTER POWER SWITCH on the
overhead control panel. Refer to Figure 2-15, Sheet 1.
Individual system circuit breakers and the associated
avionics buses are shown in Figure 2-28 and
Table 2-7. With the switch in the ON position, the
avionics power relay is de-energized and power is
applied through both 50-ampere AVIONICS MASTER
POWER #1 and #2 circuit breakers to the individual
avionics circuit breakers on the overhead circuit
breaker panel. Refer to Figure 2-16, Sheet 3.
Should the AVIONICS MASTER POWER
switch fail to operate, power to the
individual avionics circuit breakers can be
provided by pulling the 5-ampere circuit
breaker, placarded AVIONICS MASTER
CONTROL, located on the overhead circuit
In the off (aft) position, the relay is energized and
power is removed from avionics equipment. When
external power is applied to the aircraft, the avionics
power relay is normally energized, removing power
from the avionics equipment. To apply external power
to the avionics equipment, move the AVIONICS
MASTER POWER switch to the EXT PWR position.
This will de-energize the avionics power relay and
allow power to be applied to avionics equipment.
b. AC Power. Two 750-volt ampere inverters
provide ac power for the avionics equipment. The
inverters supply 115-volt and 25-volt single-phase ac
power when operated by the INVERTER #1 or #2
switches. Normally both switches will be ON for
operation. However, either inverter will provide power
for all avionics equipment requiring ac power, should
one inverter fail. 115 Vac power from the inverters is
routed through fuses and transformers in the nose
avionics compartment. The transformers provide the
required 26 Vac needed by avionics equipment.
Section II. COMMUNICATIONS
The communications equipment group consists
of the interphone, UHF command, VHF command, and
HF command systems.
3B-5. MICROPHONE SWITCHES, MICROPHONE
JACKS, AND HEADSET JACKS.
microphone jacks, and headset jacks, refer to
Chapter 3, Paragraph 3-5.