course is the reciprocal of the radial. To track on a radial, turn in the shortest direction and place
the head of the number two needle (inbound) or the tail of the number two needle (outbound)
under the heading index. Set the desired course in the course selector window of the course
indicator. Periodically check for drift due to wind, which will be indicated by the number two
needle moving away from the desired radial and by deflection of the CDI from the center.
If off course fly an intercept heading to get back on course (intercept headings are generally
more than 20 degrees, and drift correction headings are generally less than 20°). When back on
course, turn to an estimated drift correction heading (Figure 3-1). If this estimated drift
correction heading is excessive, the aircraft will fly off course into the wind. If that is the case,
turn to a heading the same as the course, and allow the wind to drift the aircraft back on course,
then establish a drift correction angle half of the first. If the initial drift correction heading is
insufficient, the aircraft will drift off course downwind. In this case, turn to again intercept the
course, and then establish a new estimated drift correction heading with a greater drift correction
angle than the first. This process is "bracketing". When the correct drift correction angle is
found, the difference between the heading and the desired course will be the "drift correction
angle" ("crab angle"). Drift correction angles may be estimated. Note that the higher the TAS,
the shallower the drift correction angle required to maintain a desired track: the correction
necessary to maintain course at 300 KTAS is about 2 degrees for each 10 knots of direct
crosswind, at 200 KTAS 3° per 10 knots, at 360 KTAS, 1-1/2°, etc.
The definition of "Direct" in the Pilot/Controller Glossary (an appendix in the Aeronautical
Information Manual, the Air Traffic Control Handbook, etc.), is helpful in understanding the
correct procedure for flying a route which includes a "direct" leg:
Direct Straight line flight between two navigational aids, fixes, points, or any combination
Cleared direct to:
ATC will occasionally clear an aircraft from their current location direct to a navigational aid.
For example, "Rocket 205, you are cleared from present position direct to the Semmes TACAN."
To proceed directly to a TACAN:
Tune and identify the station.
Turn in the shortest direction to the head of the number 2 needle.
3. Note heading and set this course in the course selector window of the course indicator.
To avoid reverse sensing in the CDI, confirm a "TO" indication in the TO-FROM indicator.
Track inbound on the radial.