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Pilot's Handbook of Aeronautical Knowledge
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Radio Navigation

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Pilot's Handbook of Aeronautical Knowledge

Preface

Acknowledgements

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

Appendix

Glossary

Index

There are four radio navigation systems available for use for
VFR navigation. These are:
• VHF Omnidirectional Range (VOR)
• Nondirectional Radio Beacon (NDB)
• Long Range Navigation (LORAN-C)
• Global Positioning System (GPS)

Very High Frequency (VHF) Omnidirectional
Range (VOR)

The VOR system is present in three slightly different
navigation aids (NAVAIDs): VOR, VOR/DME, and
VORTAC. By itself it is known as a VOR, and it provides
magnetic bearing information to and from the station. When
DME is also installed with a VOR, the NAVAID is referred
to as a VOR/DME. When military tactical air navigation
(TACAN) equipment is installed with a VOR, the NAVAID
is known as a VORTAC. DME is always an integral part of a
VORTAC. Regardless of the type of NAVAID utilized (VOR,
VOR/DME or VORTAC), the VOR indicator behaves the
same. Unless otherwise noted, in this section, VOR, VOR/
DME and VORTAC NAVAIDs are all referred to hereafter
as VORs.

The prefix "omni" means all, and an omnidirectional range
is a VHF radio transmitting ground station that projects
straight line courses (radials) from the station in all directions.
From a top view, it can be visualized as being similar to
the spokes from the hub of a wheel. The distance VOR
radials are projected depends upon the power output of the
transmitter.

The course or radials projected from the station are referenced
to magnetic north. Therefore, a radial is defined as a line of
magnetic bearing extending outward from the VOR station.
Radials are identified by numbers beginning with 001,
which is 1° east of magnetic north, and progress in sequence
through all the degrees of a circle until reaching 360. To aid
in orientation, a compass rose reference to magnetic north is
superimposed on aeronautical charts at the station location.
VOR ground stations transmit within a VHF frequency band
of 108.0–117.95 MHz. Because the equipment is VHF, the
signals transmitted are subject to line-of-sight restrictions.
Therefore, its range varies in direct proportion to the altitude
of receiving equipment. Generally, the reception range of
the signals at an altitude of 1,000 feet above ground level
(AGL) is about 40 to 45 miles. This distance increases with
altitude. [Figure 15-28]

VHF transmissions follow a line-of-sight course.
Figure 15-28. VHF transmissions follow a line-of-sight course.

VORs and VORTACs are classed according to operational
use. There are three classes:
• T (Terminal)
• L (Low altitude)
• H (High altitude)
The normal useful range for the various classes is shown in
the following table:
VOR/VORTAC NAVAIDS
Normal Usable Altitudes and Radius Distances
Distance
Class Altitudes (Miles)
T 12,000' and below 25
L Below 18,000' 40
H Below 14,500' 40
H Within the conterminous 48 states
only, between 14,500 and 17,999' 100
H 18,000'—FL 450 130
H 60,000'—FL 450 100

The useful range of certain facilities may be less than 50 miles.
For further information concerning these restrictions, refer to
the Communication/NAVAID Remarks in the A/FD.

 

15-22