Figure 1-9. TACAN/TCN-40 Control Panel

INSTRUMENT FLIGHT RULES WORKBOOK

CHAPTER ONE

information. Like VOR, TACAN provides 360 courses radiating from a station. Distance

measuring equipment, an integral part of TACAN, provides continuous slant-range distance

information. An additional advantage is that TACAN ground equipment is compact and

relatively easy to transport. This provides great versatility in beacon installation and mobility.

Stations that have VOR and TACAN systems collocated are called VORTAC stations.

The TACAN has a three-position switch. The three positions are as follows (Figure 1-9):

OFF

STBY Standby

T/R Transmit and Receive

The OFF position disconnects the unit from the aircraft power supply. In the STBY position, the

TACAN radio receives magnetic bearing information from ground TACAN navigation facilities.

This information is displayed in the cockpit by the No. 2 needle of the RMI (Figure 1-3). In the

T/R position, the TACAN radio receives magnetic bearing and distance information. The

distance from the aircraft to the TACAN navigation facility is displayed in the cockpit on the

Naval Aircraft Collision Warning System (NACWS). In the T/R position, the TACAN

determines distance by measuring the elapsed time between the transmission of an interrogating

pulse from the airborne set and the reception of the corresponding reply pulse from the ground

station.

Figure 1-9 TACAN/TCN-40 Control Panel

Although a TACAN radio is a transceiver, it cannot be used to transmit or receive voice

communications. A TACAN station will identify itself approximately every 37.5 seconds in

Morse code using its three-letter identifier. The appropriate mixer switch must be ON to hear the

identifying code.

TACAN station passage is indicated by:

Distance (DME) decreases to a minimum (primary indication),

TACAN needle rotates 180,

INTRODUCTION TO AIRBORNE NAVIGATION AND COMMUNICATIONS

EQUIPMENT AND PRINCIPLES OF OPERATION 1-13