Chapter 3A Avionicsc D1; General; Communications - Beechcraft C-12C Operator And Technical Reference Manual

3A-1. DESCRIPTION.
This chapter covers the avionics equipment
configuration installed in C-12C and C-12D1 aircraft. It
includes a brief description of the avionics equipment
and its technical characteristics, capabilities, and
locations.
3A-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
instruments under
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 an 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
installed.
3A-3. POWER SOURCE.
a. DC Power.
equipment is provided by four sources: the aircraft
battery, left and right generators, and external power.
3A-4. DESCRIPTION.
The communications equipment group consists
of the interphone, UHF command, VHF command, and
HF command systems.
3A-5. MICROPHONE SWITCHES, MICROPHONE
JACKS, AND HEADSET JACKS.
For information
microphone jacks, and headset jacks, refer to
Chapter 3, Paragraph 3-5.
CHAPTER 3A
AVIONICS
Section I. GENERAL
Instrument Meteorological
DC power for the avionics
Section II. Communications
on microphone switches,
C D1
Power is routed through two 50-ampere circuit
breakers to the avionics power relay that is controlled
by the AVIONICS MASTER switch on the overhead
control panel, Figure 2-15. Individual system circuit
breakers and the associated avionics buses are shown
in Figure 2-27 and Table 2-6. With the switch in the
ON position, the avionics power relay is de-energized
and power is applied through both 50-ampere avionics
MASTER PWR #1 and #2 circuit breakers to the
individual avionics circuit breakers on the overhead
circuit breaker panel. Refer to Figure 2-16, Sheets 1
and 2. 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 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.
equipment is provided by two inverters. The inverters
supply 115-volt and 25-volt single-phase ac power
when operated by the INVERTER #1 or #2 switches.
Either inverter will provide power for all avionics
equipment requiring ac power. 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.
3A-6. INTERPHONE SYSTEM.
a. Description. Individual audio control panels
are provided for the pilot and copilot. The controls and
switches on each provide for reception and volume
control of interphone, communication, and navigational
audio signals and a choice of transmission on UHF,
VHF, or HF transmitters. The audio control panels are
protected by two 2-ampere circuit breakers, placarded
AUDIO PILOT and AUDIO COPILOT, located on the
overhead circuit breaker panel.
TM 1-1510-218-10
AC power for the avionics
3A-1