| Home | Privacy | Contact |

Instrument Flying Handbook
Navigation Systems
Traditional Navigation Systems

| First | Previous | Next | Last |

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

Interception of Bearing.
Figure 7-9. Interception of Bearing.

The courses oriented FROM the station are called radials. The
VOR information received by an aircraft is not influenced
by aircraft attitude or heading. [Figure 7-10] Radials can
be envisioned to he like the spokes of a wheel on which the
aircraft is on one specific radial at any time. For example,
aircraft A (heading 180°) is inbound on the 360° radial; after
crossing the station, the aircraft is outbound on the 180°
radial at A1. Aircraft B is shown crossing the 225° radial.
Similarly, at any point around the station, an aircraft can be
located somewhere on a specific \'OR radial. Additionally,
a VOR needle on an RMI will always point to the course
that will take you to the VOR station where conversely the
ADF needle points to the station as a RB from the aircraft. In
the example above, the ADF needle at position A would be
pointed straight ahead, at A1 to the aircraft's 180° position
(tail) and at B, to the aircraft's right.

The VOR receiver measures and presents information to
indicate bearing TO or FROM the station. In addition to the
navigation signals transmitted by the VOR, a Morse code
signal is transmitted concurrently to identify the facility, as
well as voice transmissions for communication and relay of
weather and other information.

VORs are classified according to their operational uses. The
standard VOR facility has a power output of approximately
200 watts, with a maximum usable range depending upon
the aircraft altitude, class of facility, location of the facility,
terrain conditions within the usable area of the facility, and

other factors. Above and beyond certain altitude and distance
limits, signal interference from other VOR facilities and a
weak signal make it unreliable. Coverage is typically at least
40 miles at normal minimum instrument flight rules (IFR)
altitudes. VORs with accuracy problems in parts of their
service volume are listed in Notices to Airmen (NOTAMs)
and in the Airport/Facility Directory (A/FD) under the name
of the NAVAID.

VOR Components
The ground equipment consists of a VOR ground station,
which is a small, low building topped with a flat white disc,
upon which are located the VOR antennas and a fiberglass
cone-shaped tower [Figure 7-11] The station includes an
automatic monitoring system. The monitor automatically
turns off defective equipment and turns on the standby
transmitter, Generally, the accuracy of the signal from the
ground station is within 1º

VOR facilities are aurally identified by Morse code, or
voice, or both. The VOR can be used for ground-to-air
communication without interference with the navigation
signal. VOR facilities operate within the 108.0 to 117.95 MHz
frequency band and assignment between 108.0 and 112.0
MHz is in even-tenth increments to preclude any conflict
with ILS localizer frequency assignment, which uses the
odd tenths in this range.

VOR Radials.
Figure 7-10. VOR Radials.