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Instrument Flying Handbook
Navigation Systems
Traditional Navigation Systems

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Instrument Flying


Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Using an Electronic Flight

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight

Chapter 6. Helicopter
Attitude Instrument Flying

Chapter 7. Navigation Systems
Chapter 8. The National
Airspace System

Chapter 9. The Air Traffic
Control System

Chapter 10. IFR Flight
Chapter 11. Emergency

A single NAVAID will allow a pilot to determine the aircraft's
position relative to a radial. Indications from a second
NAVAID are needed in order to narrow the aircraft's position
down to an exact location on this radial.

Tracking TO and FROM the Station

To track to the station, rotate the OBS until TO appears, then
center the CDI. Fly the course indicated by the index. If the CDI
moves off center to the left, 'follow the needle by correcting
course to the left, beginning with a 20° correction.

When flying the course indicated on the index, a left
deflection of the needle indicates a crosswind component
from the left. If the amount! of correction brings the needle
back to center, decrease the left course correction by half. If
the CDI moves left or right now, it should do so much more
slowly, and smaller heading corrections can be made for the
next iteration.

Keeping the CDI. centered will take the aircraft to the station.
To track to the station, the OBS value at the index is not
changed. To home to the station, the CDI needle is periodically
centered, and the new course under the index is used for the
aircraft heading. Homing will follow a circuitous route to the
station, just as with ADF horning.

To track FROM the station on a VOR radial, you should
first orient the aircraft's location with respect to the station
and the desired outbound track by centering the CDI needle
with a FROM indication. The track is intercepted by either
flying over the station or establishing an intercept heading.
The magnetic course of the desired radial is entered under the
index using the OBS and the intercept heading held until the
CDI centers. Then the procedure for tracking to the station is
used to fly outbound on the specified radial.

Course Interception

If the desired course is not the one being flown, first orient
the aircraft's position with respect to the VOR station and the
course to be flown, and then establish an intercept heading.
The following steps may be used to intercept a predetermined
course, either inbound or outbound. Steps 1-3 may be omitted
when turning directly to intercept the course without initially
turning to parallel the desired course.

1. Determine the difference between the radial to be
intercepted and the radial on which the aircraft is
located (205° - 160° = 045°).

2. Double the difference to determine the interception
angle, which will not be less than 20° nor greater
than 90° (45° x 2 = 090°). 205° + 090° = 295° for the

3. Rotate the OBS to the desired radial or inbound

4. Turn to the interception heading.

5. Hold this heading constant until the CDI center, which
indicates the aircraft is on course. (With practice in
judging the varying rates of closure with the course
centerline, pilots learn to lead the turn to prevent
overshooting the course.)

6. Turn to the MH corresponding to the selected
course, and follow tracking procedures inbound or

Course interception is illustrated in Figure 7-16.

VOR Operational Errors
Typical pilot-induced errors include:

1. Careless tuning and identification of station.

2. Failure to check receiver for accuracy/sensitivity.

3. Turning in the wrong direction during an orientation.
This error is common until visualizing position rather
than heading.

4. Failure to check the ambiguity (TO/FROM) indicator,
particularly during course reversals, resulting
in reverse sensing, and corrections in the wrong

5. Failure to parallel the 'desired radial on a track
interception problem. Without this step, orientation
to the desired radial can be confusing. Since pilots
think in terms of left and right of course, aligning the
aircraft position to the radial/course is essential.

6. Overshooting and undershooting radials on interception

7. Overcontrolling corrections during tracking, especially
close to the station.

g. Misinterpretation of station passage. On VOR
receivers not equipped with an ON/OFF flag, a
voice transmission on the combined communication
and navigation radio (NAV/COM) in use for VOR
may cause the same TO/FROM fluctuations on the
ambiguity meter as shown during station passage.
Read the whole receiver TO/FROM, CDI, and
OBS before you make a decision. Do not utilize a
VOR reading observed while transmitting.

9. Chasing the CDI, resulting in homing instead of
tracking. Careless heading control and failure to
bracket wind corrections make this error common.