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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

Some DME receivers provide a groundspeed in knots by
monitoring the rate of change of the aircraft's position relative
to the ground station. Groundspeed values are accurate only
when tracking directly to or from the station.

DME Components
navigation facilities established by the FAA provide course
and distance information from collocated components under
a frequency-pairing plan. DME operates on frequencies
in the UHF spectrum between 962 MHz and 1213 MHZ.
Aircraft receiving equipment, which provides for automatic
DIME selection assures reception of azimuth and distance
information from a common source when designated VOR/
DME, VORTAC, ILS/DME, and LOC/DM-E are selected.
Some aircraft have separate VOR and DME receivers, each
of which must be tuned to the appropriate navigation facility.
The airborne equipment includes an antenna and a receiver.

The pilot controllable features of the DME receiver

Channel (Frequency) Selector
Many DMEs are channeled by an associated VHF radio, or
there may be a selector switch so a pilot can select which
VHF radio is channeling the DME. For a DME with its
own frequency selector, use the frequency of the associated
VOR/DME or VORTAC station.

On/Off/Volume Switch
The DME identifier will be heard as a Morse code identifier
with a tone somewhat higher than that of the associated VOR
or LOC. It will be heard once for every three or four times
the VOR or LOC identifier is heard. If only one identifier is
heard about every 30 seconds, the DME is functional. but
the associated VOR or LOC is not.

Mode Switch
The mode switch selects between distance (DIST) or distance
in NMs, groundspeed, and time to station. There may also
be one or more HOLD functions which permit the DME to
stay channeled to the station that was selected before the
switch was placed in the hold position. This is useful when
you make an ILS approach at a facility that has no collocated
DME, but there is a VOR/DME nearby.

Some DMEs correct for slant-range error.

Function of DME
A DME is used for determining the distance from a ground
DME transmitter. Compared to other VHF/UHF NAVAIDs,

a DME is very accurate. The distance information can be
used to determine the aircraft position or flying a track that
is a constant distance from the station. This is referred to as
a DME arc.

There are many instrument approach procedures (IAPs) that
incorporate DME arcs. The procedures and techniques given
here for intercepting and maintaining such arcs are applicable
to any facility that provides DME information. Such a facility
may or may not be collocated with the facility that provides
final approach guidance.

As an example of flying a DME arc, refer to Figure 7-37 and
follow these steps:

1. Track inbound on the OKT 325° radial, frequently
checking the DME mileage readout.

2. A 0.5 NM lead is satisfactory for groundspeeds of 150
knots or less; start the turn to the arc at 10.5 miles. At
higher groundspeeds, use a proportionately greater

DME Arc Interception.
Figure 7-17. DME Arc Interception.