INSTRUMENT FLIGHT RULES WORKBOOK
Figure 1-16 TACAN Characteristics
2. Azimuth cone of confusion. The structure of the azimuth cone of confusion over a
TACAN station (Figure 1-16/1-17) is considerably different from other NAVAIDs. The azimuth
cone can be up to 100º or more in width (approximately 15 NM wide at 40,000 feet). Indications
on the aircraft instruments make it appear even wider. Approaching the TACAN station, usable
azimuth information is lost before the actual cone is reached. This is correct even though actual
azimuth unlock is prevented by the memory circuit until after the aircraft has entered the cone.
After the cone is crossed and usable signals are regained, the search cycle extends the unusable
area beyond the actual cone. Only azimuth information is unusable in the cone of confusion;
slant range distance information continues to be displayed on the range indicator.
1-20 INTRODUCTION TO AIRBORNE NAVIGATION AND COMMUNICATIONS
EQUIPMENT AND PRINCIPLES OF OPERATION