Ground Communication Switch

CHAPTER ELEVEN

STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS

1105. GROUND COMMUNICATION SWITCH

A ground comm push-to-enable switch, placarded GND COMM PUSH, is located on the right

side of the pedestal. The switch illuminates green when pressed and allows comm on the UHF,

VHF, and intercom systems during ground operations only.

1106. UHF COMMUNICATION SYSTEM

The RTU tunes and controls the UHF transceiver through the DAU. The CDU may also tune

and control the UHF transceiver through the CDU comm page.

UHF Communication Tuning Using RTU

The top two lines show either the active channel and preset channel or the active frequency and

preset frequency. Pressing a channel or frequency line key moves the selector star to that line.

The channel or frequency may now be tuned by rotating the tuning knobs. Up to 20 preset

channels may be selected.

When the active channel or frequency is changed on the RTU, the CDU comm active frequency

is changed and the selected transceiver is tuned. The CDU old active frequency is transferred to

the recall line and the old recall frequency is discarded. When the CDU, UHF, or VHF active

frequency is changed, the RTU display is updated and the transceiver is tuned.

UHF Communication Tuning Using CDU

The RADIO TUNING page provides two frequency locations each for UHF and VHF. Each has

an active frequency (labeled UHF or VHF). The second location is either a preset frequency

(labeled UHF 1 PRE or VHF 2 PRE) or a recall frequency (labeled UHF 1 RCL or VHF 2 RCL).

To select the RADIO TUNING page, press the CDU TUN button. Enter any valid frequency in

the scratch pad line. Press UHF, VHF, UHF 1 PRE, UHF 1 RCL, VHF 2 PRE, VHF 2 RCL, or

any normal preset line key to transfer the frequency from the scratch pad line to that selected

location. If the UHF or VHF location was selected, the scratch pad frequency is entered in that

location, and the transceiver is tuned immediately. The old active frequency is transferred to the

UHF 1 RCL or VHF 2 RCL, and RECALL locations; the old recall frequencies are discarded.

1107. VHF COMMUNICATION SYSTEM

The RTU tunes and controls the VHF transceiver. The CDU may also tune and control the VHF

transceiver through the CDU RADIO TUNING and COM PRESETS page. The VHF

transceiver provides a maximum line of sight range of 160 NM.

VHF Communication Using RTU

The top two lines of the CP's RTU main menu show the active frequency and frequency with a

preset frequency labeled PRE. Pressing the frequency line key or preset frequency line key

moves the selector star to that line. The active or preset frequency, when selected, may be tuned

by rotating the tuning knobs.

11-2 RADIO SYSTEMS