Appendix C: Advanced Instrument Concepts

APPENDIX C

ADVANCED INSTRUMENT CONCEPTS

C100. GENERAL

The purpose of this section is to provide the experienced RI student with greater comprehension

of selected radio instrument topics. Before delving into these concepts be sure that you have a

solid background in the basics of RI.

The information and techniques within this Appendix should not be viewed as required

procedures but as information to use in your execution of assigned maneuvers.

C101. RADIAL SPACING

You are no doubt familiar with the concept that as your distance from a NAVAID increases, the

spacing between given radials also increase. However, just how much does radial spacing

increase as you move from the station?

To answer this question, consider the following. At a distance of 60 NM from the station, there is

one mile between each radial. As you get closer to the station, the radials are closer together.

(For example, at 30 NM from the station, there is onehalf mile between radials or two radials per

mile; at 10 NM, it is 1/6 mile between radials, which equals six radials per mile. (Figure C1) In

general, 60 divided by distance from the station equals the number of radials per mile.

Figure C-1 Radial Spacing

C102. DISTANCE FROM AIRWAY CENTERLINE

Recall that a VOR Federal Airway is 8 NM wide, 4 NM on either side of the centerline. On

some occasions, it may be helpful to estimate your distance from airway centerline.

Again, merely convert angular distance to nautical miles by the same calculation used above,

e.g., 2 south of course at 30 NM from the TACAN station equates to 1 NM south of airway

centerline.

ADVANCED INSTRUMENT CONCEPTS C-1