Pilot/Controller Glossary

8/15/19

PCG C

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7

communications during operations within a sector
are normally maintained on discrete frequencies
assigned to the sector.

(See DISCRETE FREQUENCY.)

CONTROL SLASH

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 A radar beacon slash repre-

senting the actual position of the associated aircraft.
Normally, the control slash is the one closest to the
interrogating radar beacon site. When ARTCC radar
is operating in narrowband (digitized) mode, the
control slash is converted to a target symbol.

CONTROLLED AIRSPACE

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 An airspace of

defined dimensions within which air traffic control
service is provided to IFR flights and to VFR flights
in accordance with the airspace classification.

a.

Controlled airspace is a generic term that covers

Class A, Class B, Class C, Class D, and Class E
airspace.

b.

Controlled airspace is also that airspace within

which all aircraft operators are subject to certain pilot
qualifications, operating rules, and equipment
requirements  in  14 CFR  Part 91  (for  specific
operating requirements, please refer to 14 CFR
Part 91). For IFR operations in any class of controlled
airspace, a pilot must file an IFR flight plan and
receive an appropriate ATC clearance. Each Class B,
Class C, and Class D airspace area designated for an
airport contains at least one primary airport around
which the airspace is designated (for specific
designations and descriptions of the airspace classes,
please refer to 14 CFR Part 71).

c.

Controlled airspace in the United States is

designated as follows:

1.

CLASS A

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 Generally, that airspace from

18,000 feet MSL up to and including FL 600,
including the airspace overlying the waters within 12
nautical miles of the coast of the 48 contiguous States
and Alaska. Unless otherwise authorized, all persons
must operate their aircraft under IFR.

2.

CLASS B

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 Generally, that 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 and
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 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. The cloud clearance requirement for VFR
operations is “clear of clouds.”

3.

CLASS C

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 Generally, that 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 that have a certain
number of IFR operations or passenger enplane-
ments. Although the configuration of each Class C
area is individually tailored, the airspace usually
consists of a surface area with a 5 nautical mile (NM)
radius, a circle with a 10NM radius that extends no
lower than 1,200 feet up to 4,000 feet above the
airport elevation, and an outer area that is not charted.
Each person must establish two-way radio commu-
nications with the ATC facility providing air traffic
services prior to entering the airspace and thereafter
maintain those communications while within the
airspace. VFR aircraft are only separated from IFR
aircraft within the airspace.

(See OUTER AREA.)

4.

CLASS D

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 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 may be Class D or Class E
airspace. Unless otherwise authorized, each person
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. No separation
services are provided to VFR aircraft.

5.

CLASS E

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 Generally, if the airspace is not

Class A, Class B, Class C, or Class D, and it is
controlled airspace, 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 AGL used to transition to/from the terminal or en
route environment, en route domestic, and offshore
airspace areas designated below 18,000 feet MSL.
Unless designated at a lower altitude, Class E