7. Double needle on RMI Read course
To operate set for sense antenna direction
finding: 1. Mode selector ANT.
2. Range switch Select.
3. TUNE control rotate for maximum
reading on tuning meter.
4. GAIN control As required.
To operate set for audio-null direction
1. Mode selector ANT.
2. BFO-OFF switch BFO.
3. Range switch select.
4. TUNE control Tune desired station.
5. GAIN control Adjust for minimum
6. Double needle switches (RMI, fig. 3-
9) As required.
7. BFO-OFF switch OFF.
8. Mode selector LOOP.
9. LOOP switch L or R. Turn left or
(minimum sound in headsets).
10. Double needle on RMI (fig. 3-9)
Read course to station.
The true null and direction to the
radio station may be indicated by
either end of the single needle.
This ambiguity must be solved to
determine proper direction to the
Shutdown. Mode selector OFF.
3-26. TACAN SYSTEMS.
Description. Two Tactical Air Navigation
(TACAN) systems are provided. One is dedicated to the
INS and is used only for position updating; the other is
used in conjunction with other avionics systems,
including the flight director system and the autopilot.
TACAN is a radio navigation system which provides
aircraft distance and bearing information relative to a
TACAN ground station. Both systems operate in the L-
band frequency range of 962 to 1213 MHz.
Their range, though limited to line-of-sight, is designed
to provide reliable reception of a TACAN ground station
at a distance of 170 nautical miles at an aircraft altitude
of 20,000 feet. The normal time required for the
systems to lock on to a selected ground station signal is
three seconds. The avionics TACAN system is
protected by the 2ampere TACAN circuit breaker
located on the overhead circuit breaker panel (fig. 2-
Avionics TACAN System. The AN/ARN136(V)
avionics TACAN system consists of the RT1321
receiver-transmitter and the CP-1398 azimuth computer,
both of which are located in the right nose avionics
compartment; the ID-2218 range indicator, located on
the instrument panel, the C-11265 control panel, located
in the pedestal extension; and an antenna located on
the top surface of the aircraft fuselage. The avionics
TACAN system operates in conjunction with TACAN and
VORTAC ground stations to provide distance, ground
speed, time-to-station, and bearing-to-station data. It
operates in the L band frequency range on one of 252
pre-selected frequencies, 126 X mode and 126 Y mode
channels. Course deviation from TACAN stations is
displayed on the HSI. Distance, time-to-station, and
ground speed are displayed on the TACAN digital
display (fig. 3-17). The ground speed and time-to-
station are accurate only if the aircraft is flying directly
toward the ground station at a sufficient distance that
the slant range and ground range are nearly equal.
The avionics TACAN system may be operated by
the flight director system or connected to and used with
the autopilot system. When employed as the primary
means of navigation, aircraft flight may be controlled
manually or by the autopilot. Indications of aircraft
heading and bearing to ground stations are displayed on
the course deviation indicators (HSIs). Relative bearing
to a station is displayed by the RMI bearing pointer.
TACAN distance, ground speed, and time-to-station are
all displayed on the TACAN indicator located on the
copilot's instrument panel (fig. 2-28).
The TACAN control panel (fig. 3-17) enables
selection of the TACAN frequency (channel) to be used,
and provides for self-test of TACAN circuits. X or Y
channel is selected by the X/Y switch. Most TACAN and
VORTAC stations are operated on the X mode. When Y
mode stations are operational, air navigation charts will
designate the Y mode stations. A toggle switch provides
system power ON/OFF control. Audio control is
provided by a rotary control placarded VOL.
INS TACAN System. The INS TACAN system
is of the same type as the avionics TACAN system.
This set, inaccessible to pilot control, is coupled directly