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Instrument Flying Handbook
The National Airspace System
IFR En Route Charts

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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

NDBs, localizers, and off-route VORs are used to establish
intersections. NDBs are sometimes collocated with
intersections, in which case passage of the NDB would mark
the intersection. A bearing to an off-route NDB also can
provide intersection identification. A localizer course used to
identify an intersection is depicted by a feathered arrowhead
symbol on the en route chart.
If feathered markings appear on the left-hand side of the
arrowhead, a back course (BC)
signal is transmitted. On NACG en route charts, the localizer
symbol is only depicted to identify an intersection.

Off-route VORs remain the most common means of
identifying intersections when traveling on an airway. Arrows
depicted next to the intersection indicate the NAVAID to
be used for identification. Another means of identifying an
intersection is with the use of DME. A hollow arrowhead
indicates DME is authorized for intersection identification. If
the DME mileage at the intersection is a cumulative distance
of route segments, the mileage is totaled and indicated by
a D-shaped symbol with a mileage number inside.
[Figure 8-4] Approved IFR GPS units can also be used to
report intersections.

Other Route Information
DME and GPS provide valuable route information concerning
such factors as mileage, position, and groundspeed. Even
without this equipment, information is provided on the
charts for making the necessary calculations using time and
distance. The en route chart depicts point-to-point distances
on the airway system. Distances from VOR to VOR are
charted with a number inside of a box. To differentiate
distances when two airways coincide, the word "TO" with the
three-letter VOR identifier appear to the left of the distance
boxes. TO PDX

VOR changeover points (COPs) are depicted on the charts by
this symbol: The numbers indicate the distance at which
to change the VOR frequency. The frequency change might
be required due to signal reception or conflicting frequencies.
If a COP does not appear on an airway, the frequency should
be changed midway between the facilities. A COP at an
intersection may indicate a course change.

Occasionally an "x" will appear at a separated segment of
an airway that is not an intersection. The "x" is a mileage
breakdown or computer navigation fix and may indicate a
course change.

Today's computerized system of ATC has greatly reduced
the need for holding en route. However,

published holding patterns are still found on charts at junctures where ATC has deemed it necessary to enable traffic flow.
When a holding pattern is charted, the controller may provide
the holding direction and the statement "as published."
[Figure 8-4]

Boundaries separating the jurisdiction of Air Route Traffic
Control Centers (ARTCC) are depicted on charts with blue
serrations. The name
of the controlling facility is printed on the corresponding side of
the division line. ARTCC remote sites are depicted as blue
serrated boxes and contain the center name, sector name, and
the sector frequency. [Figure 8-4]

Weather information and Communication Features
En route NAVAIDs also provide weather information and
serve communication functions.
When a NAVAID is shown as a shadowed box, an automated
flight service station (AFSS) of the same name is directly
associated with the facility. If an AFSS is located without an
associated NAVAID, the shadowed box is smaller and contains
only the name and identifier. The AFSS frequencies are
provided above the box. (Frequencies 122.2 and 255.4, end
emergency frequencies 121.5 and
243.0 are not listed.)

A Remote Communications Outlet (RCO) associated with
a NAVAID is designated by a thin-
lined box with the controlling AFSS frequency above the box,
and the name under the box. Without an associated facility,
the thin - lined RCO box contains the AFSS name and remote

Automated Surface Observing Station (ASOS), Automated
Weather Observing Station (AWOS), Hazardous In-flight
Weather Advisory Service (HIWAS) and Transcribed Weather
Broadcast (TWEB) are continuously
transmitted over selected NAVAIDs and depicted in the
NAVAID box. ASOS/AWOS are depicted by a white "A",
HIWAS by a "H" and TWEB broadcasts by a "T" in a solid black
circle in the upper right or left corner.