Section I. GENERAL
Except for mission avionics, this chapter covers
all avionics equipment installed in the RC-12K aircraft.
It provides a brief description of the equipment, the
technical characteristics and locations. It covers
systems, controls, and provides the proper techniques
and procedures to be employed when operating the
equipment. For more detailed operational information
consult the vendor manuals that accompany the aircraft
AVIONICS EQUIPMENT CONFIGURATION.
The aircraft avionics covered, consists of three
groups of electronic equipment. The communication
group consists of the interphone, UHF command, BU
VOW, VHF FM, VHF command and HF command
systems. The navigation 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 Instrument
Meteorological Conditions (IMC). The navigation group
includes equipment for determining altitude, attitude,
position, destination, range and bearing, heading
transponder and radar group includes an identification,
position, emergency tracking system, a radar system to
locate potentially dangerous weather areas, and a radar
system to differentiate between friendly and unfriendly
All avionics equipment require a 3-
minute warmup period. The weather
radar has an automatic time delay of 3
to 4 minutes.
DC Power. DC power for the avionics
equipment is provided by four sources: the aircraft
battery, left and right generators, and external power.
Power is routed through two 50-ampere circuit breakers
to the avionics power relay which is controlled by the
AVIONICS MASTER POWER switch in the overhead
control panel (fig. 2-13). Individual system circuit
breakers and the associated avionics busses are shown
in figure 2-6. With the switch in the ON (forward)
position, the avionics power relay is de-energized and
power is applied through both the AVIONICS MASTER
POWER No. 1 and No. 2 circuit breakers to the
individual avionics circuit breakers in the overhead
circuit breaker panel (fig. 2-6). In the OFF (aft)
position, the relay is energized and power is removed
from the avionics equipment.
If the AVIONICS MASTER POWER
switch fails to operate, power to the
individual avionics circuit breakers
can be provided by pulling the 5-
ampere circuit breaker, placarded
AVIONICS MASTER CONTR, located
in the overhead circuit breaker panel
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 the avionics equipment.
Single-Phase AC Power. AC power for the
avionics equipment is provided by two inverters. The
inverters supply 115-volt and 26-volt singlephase AC
power when operated by the INVERTER No. 1 or No. 2
switches (fig. 2-13). Either inverter is capable of
powering all avionics equipment requiring AC power.
AC power from the inverters is routed through fuses
located in the nose avionics compartment.
Three-Phase AC Power. Three phase AC
electrical power for operation of the inertial navigation
system and mission avionics is supplied by two DC
powered, 3000 volt-ampere, solid state, three phase
inverters. The three phase inverters are controlled by
two three-position switches located in the mission
control panel (fig. 4-1) placarded No. 1 INV OFF ON
RESET and No. 2 INV OFF ON RESET.