time for 30 45 seconds. Maintain cruise airspeed. At the end of your
"outbound timing" make a turn to intercept the initial approach course inbound.
TAILRADIALTURN (see Figure 659). Proceed inbound to the IAF.
Figure 659 Maneuvering Turn
Arc/Radial Intercepts On some TACAN approaches, missed approaches and departure
procedures, you will be required to fly an arc and then intercept a radial (inbound or outbound)
from that arc. In this situation you have to decide when to start your turn off the arc to intercept
the radial. You should already be familiar with judging turns off an arc based on needle and CDI
movements. However, there is a more refined method available. This method utilizes Radial
Spacing (Appendix C) and Radius of Turn (pg. 6 58).
Figure 660 illustrates a typical situation. Determine when to turn off the arc to fly inbound on
the 360º radial (180º course).
Determining Lead Radials:
Determine the number of radials per mile. Recall from Appendix C that 60
divided by DME equals the number of radials in one mile.
In this example: 60/12 = Five radials per mile on the 12 DME arc.
Calculate the turn radius of the aircraft. This is 5% of the groundspeed. At 120
knots, the turn radius is .6 NM.
Multiply the turn radius by the number of radials per mile. .6 NM X 5
radials/NM = 3 radials
6-98 RADIO INSTRUMENT FLIGHT PROCEDURES