Navigation Tuning Using the RTU

CHAPTER TWELVE

STUDENT GUIDE FOR T-1A AIRCRAFT SYSTEMS

1203. NAVIGATION TUNING USING THE RTU

The third line of the P and CP RTU displays the nav receiver's active frequencies. FMS

automatic tuning mode may also be displayed. The large knob changes the hundreds, tens, and

units digits in one-MHz increments. The small tuning knob changes the tenths and hundredths

digits in 0.50-Hz increments.

1204. NAVIGATION TUNING USING THE CDU

The nav receivers may be tuned or controlled by the CDU when the CDU RADIO TUNING and

NAV PRESETS pages are selected. When the RTU active nav frequency is changed, the CDU

nav page active frequency is automatically updated to the same frequency. The old CDU active

frequency is transferred to the recall line. When the active frequency is changed on the CDU,

the RTU active frequency is updated.

1205. TACTICAL AIR NAVIGATION SYSTEM

The TACAN system provides slant range distance, relative bearing, velocity, time-to-station, and

audio identification information to a selected TACAN or DME ground station. TACAN

information is displayed on both P's EADI and EHSI and the MFD. The TACAN system

consists of a TACAN transmitter/receiver and upper and lower antennas.

TACAN Tuning Using the RTU

The fifth line of the P's RTU displays the TACAN active code. Pressing the TCN line key

moves the selector star to that line. The code may now be changed using the tuning knobs. The

RTU large tuning knob changes the hundreds and tens digits from 1 to 12. The small tuning

knob changes the units digits from 0 to 9X and then from 0 to 9Y.

TACAN Tuning Using the CDU

The TACAN may be tuned by the CDU when the CDU RADIO TUNING and RADIO

PRESETS pages are selected. Enter any valid code in the scratch pad line. Press either TACAN

or any preset line key to transfer the code from the scratch pad line to that selected location. If

the TACAN location was selected, the old TACAN code is discarded, and the TACAN is tuned

to the new code. If the code entered is invalid or out of range, the CDU last line displays an

error message. The RTU has tuning priority over the CDU.

1206. AIR TRAFFIC CONTROL TRANSPONDER SYSTEM

The ATC transponder system provides aircraft identification and altitude reporting information

for the Air Traffic Control and Radar Beacon System (ATCRBS). The ATC transponder system

also provides altitude coding information to the TCAS. The transponder system consists of a

transponder located in the avionics rack, an ident pushbutton switch located on each of the

control wheels, and two antennas.

12-2 NAVIGATION RADIOS