PRIMUS
r
1000 Integrated Avionics System
A28--1146--112--00
C--7
PRIMUS
â
II Radio System
Tuning Backup Control Head
The tuning backup control head is an additional backup system that
controls the copilot’s VOR receiver and communication transceiver.
RADIO MANAGEMENT UNIT (RMU) OPERATION
General
The RMU is the central control unit for the radio system. Two RMUs are
mounted on the center pedestal, forward of the engine throttle
quadrants.
The RMU is used to control operating modes, frequencies, and codes
in all the units of the PRIMUS
â
II radio system. Frequencies can also
be controlled by a radio control input from an external flight
management system (FMS). When the FMS tunes the radios, the
digital signals from the FMS come into the integrated radio system
where they act as if the RMU tuning knob were being operated. For
detailed FMS operation, refer to the applicable FMS operating
procedures. A third frequency control method uses the tuning backup
control head.
The RMU is also used to control the TCAS, a TCAS II system, that
displays conflict resolution advisories in the form of vertical guidance.
The RMU screen is divided into several dedicated windows. Each
window groups the data associated with a function. The windows,
COM, NAV, transponder, ATC/TCAS, and ADF, each control both the
frequency and operating mode of the associated function. The RMU
has other display modes, called pages, that control additional features
of the radio system.
The RMU is accomplished through the use of line select keys, function
keys, and concentric tuning knobs. Any selectable parameter, such as
a radio frequency, can be changed by pushing the line key next to the
displayed parameter. This places a cursor box around that parameter.
The values for that parameter can be set by rotating the tuning knobs.
On the ground, the RMU initiates a system power--on self--test when
power is first applied, or with weight--on--wheels (WOW) when power
has been off more than 10 seconds.
