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
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