| Home | Privacy | Contact |

Instrument Flying Handbook
The National Airspace System
IFR En Route Charts

| 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

Tower En Route Control (TEC) is an ATC program that
uses overlapping approach control radar services to provide
IFR clearances. By using TEC, a pilot is routed by airport
control towers. Some advantages include abbreviated filing
procedures and reduced traffic separation requirements. TEC
is dependent upon the ATC's workload, and the procedure
varies among locales.

The latest version of Advisory Circular (AC) 90-91, North
American Route Program (NRP), provides guidance to users
of the NAS for participation in the NRP. All flights operating
at or above FL 290 within the conterminous United States
and Canada are eligible to participate in the NRP, the primary
purpose of which is to allow operators to plan minimum time!
cost routes that may be off the prescribed route structure. NRP
aircraft are not subject to route-limiting restrictions (e.g.,
published preferred IFR routes) beyond a 200 NM radius of
their point of departure or destination.

IFR En Route Charts

The objective of IFR en route flight is to navigate within the
lateral limits of a designated airway at an altitude consistent
with the ATC clearance. Your ability to fly instruments
safely and competently in the system is greatly enhanced by
understanding the vast array of data available to the pilot on
instrument charts. The NACG maintains and produces the
charts for the United States government.

En route high-altitude charts provide aeronautical information
for en route instrument navigation (IFR) at or above 18,000
feet MSL. Information includes the portrayal of Jet and
RNAV routes, identification and frequencies of radio aids,
selected airports, distances, time zones, special use airspace,
and related information. Established Jet routes from 18,000
feet MSL to FL 450 use NAVAIDs not more than 260 NM
apart. The charts are revised every 56 days.

To effectively depart from one airport and navigate en route
under instrument conditions a pilot needs the appropriate IFR
en route low-altitude chart(s). The IFR low altitude en route
chart is the instrument equivalent of the Sectional chart. When
folded, the cover of the NACG en route chart displays an
index map of the United States showing the coverage areas.
Cities near congested airspace are shown in black type and
their associated area chart is listed in the box in the lower
left-hand corner of the map coverage box. Also noted is an
explanation of the off-route obstruction clearance altitude
(OROCA). The effective date of the chart is printed on the
other side of the folded chart. information concerning MTRs
is also included on the chart cover. The en route charts are
revised every 56 days.

When the NACG en route chart is unfolded, the legend is
displayed and provides information concerning airports,
NAVAIDs, communications, air traffic services, and

Airport Information
Airport information is provided in the legend, and the symbols
used for the airport name, elevation, and runway length are
similar to the sectional chart presentation. Associated city
names are shown for public airports only. FAA identifiers are
shown for all airports. ICAO identifiers are also shown for
airports outside of the contiguous United States, instrument
approaches can be found at airports with blue or green
symbols, while the brown airport symbol denotes airports
that do not have instrument approaches . Stars are used to
indicate the part-time nature of tower operations, ATIS
frequencies, part-time or on request lighting facilities, and
part-time airspace classifications. A box after an airport name
with a "C' or "D" inside indicates Class C and D airspace,
respectively, per Figure 8-3.

Charted IFR Altitudes
The minimum en route altitude (MEA) ensures a navigation
signal strong enough for adequate reception by the aircraft
navigation (NAV) receiver and obstacle clearance along the
airway. Communication is not necessarily guaranteed with
MEA compliance. The obstacle clearance, within the limits of
the airway, is typically 1,000 feet in non-mountainous areas
and 2,000 feet in designated mountainous areas. MEAs can
be authorized with breaks in the signal coverage; if this is the
case, the NACG en route chart notes "MEA GAP" parallel
to the affected airway. MEAs are usually bi-directional;
however, they can be single-directional. Arrows are used to
indicate the direction to which the MEA applies.

The minimum obstruction clearance altitude (MOCA), as
the name suggests, provides the same obstruction clearance
as an MEA; however, the NAV signal reception is ensured
only within 22 NM of the closest NAVAID defining the route.
The MOCA is listed below the MEA and indicated on NACG
charts by a leading asterisk (e.g., "3400" - see Figure 8-2,
V287 at bottom left).

The minimum reception altitude (MRA) identifies the lowest
altitude at which an intersection can be determined from an
off-course NAVAID. If the reception is line-of-sight based,
signal coverage will only extend to the MRA or above.
However, if the aircraft is equipped with distance measuring
equipment (DME) and the chart indicates the intersection can
be identified with such equipment the pilot could define the
fix without attaining the MRA. On NACG charts, the MRA
is indicated by the symbol and the altitude preceded by
"MRA" (e.g., "MRA 9300"). [figure 8-2]