T-6A INSTRUMENT NAVIGATION
Figure 3-1 VOR Navigation
The above example concerned EHSI indications with the aircraft at a fixed position. Let us now
consider the changes in EHSI indications produced by a moving aircraft.
The following examples assume no wind conditions.
When flying either directly inbound to or outbound from a NAVAID, you will be maintaining a
constant course and staying on the same radial. In Figure 3-2, aircraft "A" is flying inbound to
the NAVAID with a heading of 135°. The position of the aircraft is northwest of the NAVAID
on the 315° radial. It stays on the same radial despite the fact its geographical position changes
(moves closer to the station).
Aircraft "B" in Figure 3-2 is outbound from the NAVAID with a heading of 225°. Again the
geographical position changes but the aircraft remains on the 225° radial.
If you fly a heading that does not take you directly inbound or outbound in relation to a
NAVAID, your position relative will change. In Figure 3-2, while maintaining a heading of
360°, aircraft "C's" position changes from southeast of the NAVAID on the 135° radial to
northeast of the NAVAID on the 045° radial.
Figure 3-2 illustrates two important principles:
The tail of the needle always indicates which radial the aircraft is on.
2. Maintaining a constant heading if not flying directly to or from a NAVAID, will cause the
tail of the needle to rise and the head to fall (assuming no wind conditions).
FUNDAMENTALS OF INSTRUMENT NAVIGATION