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Instrument Flying Handbook
The National Airspace System
Airspace Classification

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Instrument Flying
Handbook

Preface

Table of Contents

Chapter 1. Human Factors
Chapter 2. Aerodynamic Factors
Chapter 3. Flight Instruments
Chapter 4. Section I
Airplane Attitude Instrument
Flying
Using Analog Instrumentation
Chapter 4. Section II
Airplane Attitude Instrument
Flying
Using an Electronic Flight
Display

Chapter 5. Section I
Airplane Basic
Flight Maneuvers
Using Analog Instrumentation
Chapter 5. Section II
Airplane Basic
Flight Maneuvers
Using an Electronic Flight
Display

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
Operations

Airspace Classification

Airspace in the United States [Figure 8-1] is designated as
follows:

1. Class A. Generally, airspace from 18,000 feet mean
sea level (MSL) up to and including flight level (FL)
600, including the airspace overlying the waters
within 12 nautical miles (NM) of the coast of the
48 contiguous states and Alaska. Unless otherwise
authorized, all pilots must operate their aircraft under
instrument flight rules (IFR).

2. Class B. Generally, airspace from the surface to 10,000
feet MSL surrounding the nation's busiest airports in
terms of airport operations or passenger enplanements.
The configuration of each Class B airspace area is
individually tailored, consists of a surface area and two
or more layers (some Class B airspace areas resemble
upside-down wedding cakes), and is designed to
contain all published instrument procedures once
an aircraft enters the airspace. An air traffic control
(ATC) clearance is required for all aircraft to operate
in the area, and all aircraft that are so cleared receive
separation services within the airspace.

3. Class C. Generally, airspace from the surface to
4,000 feet above the airport elevation (charted
in MSL) surrounding those airports that have an
operational control tower, are serviced by a radar
approach control, and have a certain number of IFR
operations or passenger enplanements. Although the
configuration of each Class C area is individually
tailored, the airspace usually consists of a surface
area with a 5 NM radius, an outer circle with a 10 NM
radius that extends from 1,200 feet to 4,000 feet above
the airport elevation and an outer area. Each aircraft
must establish two-way radio communications with
the ATC facility providing air traffic services prior
to entering the airspace and thereafter maintain those
communications while within the airspace.

4. Class D. Generally, that airspace from the surface
to 2,500 feet above the airport elevation (charted
in MSL) surrounding those airports that have an
operational control tower. The configuration of
each Class D airspace area is individually tailored
and when instrument procedures are published,
the airspace will normally be designed to contain
the procedures. Arrival extensions for instrument
approach procedures (IAPs) may be Class D or Class
E airspace. Unless otherwise authorized, each aircraft
must establish two-way radio communications with
the ATC facility providing air traffic services prior
to entering the airspace and thereafter maintain those
communications while in the airspace.

5. Class E. Generally, if the airspace is not Class A, B,
C, or D, and is controlled airspace, then it is Class E
airspace. Class E airspace extends upward from either
the surface or a designated altitude to the overlying
or adjacent controlled airspace. When designated as a
surface area, the airspace will be configured to contain
all instrument procedures. Also in this class are federal
airways, airspace beginning at either 700 or 1,200 feet
above ground level (AGL) used to transition to and
from the terminal or en route environment, and en
route domestic and offshore airspace areas designated
below 18,000 feet MSL. Unless designated at a lower
altitude, Class E airspace begins at 14,500 MSL over
the United States, including that airspace overlying the
waters within 12 NM of the coast of the 48 contiguous
states and Alaska, up to but not including 18,000 feet
MSL, and the airspace above FL 600.

6. Class G. Airspace not designated as Class A, B, C, D,
or E. Class G airspace is essentially uncontrolled by
ATC except when associated with a temporary control
tower.

Special Use Airspace
Special use airspace is the designation for airspace in which
Certain activities must be confined, or where limitations
may be imposed on aircraft operations that are not part
of those activities. Certain special use airspace areas can
create limitations on the mixed use of airspace. The special
use airspace depicted on instrument charts includes the
area name or number, effective altitude, time and weather
conditions of operation, the controlling agency, and the chart
panel location. On National Aeronautical Charting Group
(NACG) en route charts, this information is available on one
of the end panels.

Prohibited areas contain airspace of defined dimensions
within which the flight of aircraft is prohibited. Such areas
are established for security or other reasons associated with
the national welfare. These are published in the Federal
Register and are depicted on aeronautical charts. The area is
charted as a "P" followed by a number (e.g., "P-123").

Restricted areas are areas where operations are hazardous to
nonparticipating aircraft and contain airspace within which
the flight of aircraft while not wholly prohibited, is subject
to restrictions. Activities within these areas must be confined
because of their nature, or limitations may be imposed upon
aircraft operations that are not a part of those activities, or
both. Restricted areas denote the existence of unusual, often
invisible, hazards to aircraft (e.g., artillery firing, aerial

 
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