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Pilot's Handbook of Aeronautical Knowledge

Radio Navigation

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Pilot's Handbook of Aeronautical Knowledge



Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making




Confusion is possible when navigating an aircraft with VOR/
DME-based RNAV, and it is essential that the pilot become
familiar with the equipment installed. It is not unknown for
pilots to operate inadvertently in one of the RNAV modes
when the operation was not intended by overlooking switch
positions or annunciators. The reverse has also occurred with
a pilot neglecting to place the unit into one of the RNAV
modes by overlooking switch positions or annunciators.
As always, the prudent pilot is not only familiar with the
equipment used, but never places complete reliance in just
one method of navigation when others are available for

Automatic Direction Finder (ADF)
Many general aviation-type aircraft are equipped with ADF
radio receiving equipment. To navigate using the ADF, the
pilot tunes the receiving equipment to a ground station known
as a nondirectional radio beacon (NDB). The NDB stations
normally operate in a low or medium frequency band of
200 to 415 kHz. The frequencies are readily available on
aeronautical charts or in the A/FD.

All radio beacons except compass locators transmit a
continuous three-letter identification in code except during
voice transmissions. A compass locator, which is associated
with an instrument landing system, transmits a two-letter

Standard broadcast stations can also be used in conjunction
with ADF. Positive identification of all radio stations is
extremely important and this is particularly true when using
standard broadcast stations for navigation.

NDBs have one advantage over the VOR. This advantage is
that low or medium frequencies are not affected by line-of sight.
The signals follow the curvature of the Earth; therefore,
if the aircraft is within the range of the station, the signals
can be received regardless of altitude.

The following table gives the class of NDB stations, their
power, and usable range:
(Usable Radius Distances for All Altitudes)
Power Distance
Class (Watts) (Miles)
Compass Locator Under 25 15
MH Under 50 25
H 50–1999 *50
HH 2000 or more 75
*Service range of individual facilities may be less than 50

One of the disadvantages that should be considered when
using low frequency (LF) for navigation is that low frequency
signals are very susceptible to electrical disturbances, such as
lightning. These disturbances create excessive static, needle
deviations, and signal fades. There may be interference from
distant stations. Pilots should know the conditions under
which these disturbances can occur so they can be more alert
to possible interference when using the ADF.

Basically, the ADF aircraft equipment consists of a tuner,
which is used to set the desired station frequency, and the
navigational display.

The navigational display consists of a dial upon which the
azimuth is printed, and a needle which rotates around the dial
and points to the station to which the receiver is tuned.
Some of the ADF dials can be rotated to align the
azimuth with the aircraft heading; others are fixed with 0°
representing the nose of the aircraft, and 180° representing
the tail. Only the fixed azimuth dial is discussed in this
handbook. [Figure 15-36]

ADF with fixed azimuth and magnetic compass.
Figure 15-36. ADF with fixed azimuth and magnetic compass.

Figure 15-37 illustrates terms that are used with the ADF
and should be understood by the pilot.

To determine the magnetic bearing "FROM" the station,
180° is added to or subtracted from the magnetic bearing to
the station. This is the reciprocal bearing and is used when
plotting position fixes.