TACAN - P-340_wch40093

T-34C INSTRUMENTS

CHAPTER FOUR

404.

TACAN

Reference: T34C NATOPS Manual, Chapter 19, "TACAN Radio (TCN40)"; NIFM Part V,

"Tactical Air Navigation (TACAN)"; AIM, Chapter 1, Section 1, "Tactical Air Navigation

(TACAN)."

Tactical Air Navigation is used for airways Flight and Instrument approaches and for tactical

control of aircraft. TACAN is a navigational aid which provides azimuth and slant range distance

(DME) information to the pilot, enabling precise fixing of geographical position at all times.

TACAN stations operate in the UHF range (962 to 1213 MHz), are selected by dialing one of 252

"X" or "Y" channels, and are identified by an aural Morse Code repeating every 35 seconds. As

with VOR, reception range is limited by line of sight and is not affected by weather. Most

airways in the United States are defined by combination VOR and TACAN stations (VORTAC),

which provide VOR and TACAN azimuth and TACAN distance (DME) at one site. The VOR

portion of the facility is identified by a coded tone modulated at 1020 HMz or a combination of

tone and voice. The TACAN is identified by a coded tone modulated at 1350 HMz, transmitted

one time for each three or four times that the VOR is transmitted. DME furnishes reliable, line of

sight, SLANT RANGE information at distances up to 199 NM with an accuracy of 2 mile or 3%

of the distance, whichever is greater.

The T34C carries the TCN40 TACAN unit. As with the VOR, the receiver is located in the

avionics compartment and controlled by a receiver control box in the multifunction panel

(Figure 43). TACAN information is displayed on the TACAN needle (double bar) of the RMI

(Figure 46). Additionally, distance information is displayed on the NACWS in each cockpit

(Figures 44 and 45).

405.

NACWS

Reference: T34C NATOPS Manual, Chapter 19, "Naval Aircraft Collision Warning System

(NACWS 991)."

The Naval Aircraft Collision Warning System (NACWS) is a collision warning system used to

alert the pilot to other aircraft that are, or are likely to become, a threat of midair collision. The

system is based on a passive or nontransmitting mode of operation enhanced by an active mode

of operation. The NACWS equipment consists of a Transmitter/Receiver/Computer (TRC), two

Control/Display Units (CDU) (Figures 44 and 45), an Extended Remote Rack, two LBan

Antennas, and a Global Positioning System (GPS) antenna. The NACWS startup selftest is

automatically initiated when the NACWS is turned on.

On the Primary DME screen (Figure 4-4), the NACWS displays heading, DME, date, Zulu time,

range scale, and LAT/LONG.

On the proximity screen (Figure 4-5), the NACWS displays heading, DME, selected range scale

and potential threats.

NOTE

When a "threat" is identified by NACWS, and you are on an IFR

INTRODUCTION TO RADIO INSTRUMENTS 4-5