4. This program is not to be interpreted as
relieving pilots of their responsibilities to see and
avoid other traffic operating in basic VFR weather
conditions, to adjust their operations and flight path
as necessary to preclude serious wake encounters, to
maintain appropriate terrain and obstruction clear-
ance or to remain in weather conditions equal to or
better than the minimums required by 14 CFR
Section 91.155. Approach control should be advised
and a revised clearance or instruction obtained when
compliance with an assigned route, heading and/or
altitude is likely to compromise pilot responsibility
with respect to terrain and obstruction clearance,
vortex exposure, and weather minimums.
(See TBL 3-2-1.)
Class C Airspace Areas by State
These states currently have designated Class C
airspace areas that are depicted on sectional charts.
Pilots should consult current sectional charts and
NOTAMs for the latest information on services
available. Pilots should be aware that some Class C
airspace underlies or is adjacent to Class_B airspace.
TBL 3-2-1
Class C Airspace Areas by State
State/City Airport
ALABAMA
Birmingham . . . . . . . . . International
Huntsville . . . . . . . . . . . International-Carl T Jones Fld
Mobile . . . . . . . . . . . . . . Regional
ALASKA
Anchorage . . . . . . . . . . . International
ARIZONA
Davis-Monthan . . . . . . . AFB
Tucson . . . . . . . . . . . . . . International
ARKANSAS
Fayetteville (Springdale) Northwest Arkansas Regional
Little Rock . . . . . . . . . . Adams Field
CALIFORNIA
Beale . . . . . . . . . . . . . . . AFB
Burbank . . . . . . . . . . . . Burbank-Glendale-Pasadena
Fresno . . . . . . . . . . . . . . Air Terminal
Monterey . . . . . . . . . . . . Peninsula
Oakland . . . . . . . . . . . . . Metropolitan Oakland
International
Ontario . . . . . . . . . . . . . International
Riverside . . . . . . . . . . . . March AFB
Sacramento . . . . . . . . . . International
San Jose . . . . . . . . . . . . International
Santa Ana . . . . . . . . . . . John Wayne/Orange County
Santa Barbara . . . . . . . . Municipal
COLORADO
Colorado Springs . . . . . Municipal
CONNECTICUT
Windsor Locks . . . . . . . Bradley International
FLORIDA
Daytona Beach . . . . . . . Regional
Fort Lauderdale . . . . . . . Hollywood International
Fort Myers . . . . . . . . . . SW Florida Regional
Jacksonville . . . . . . . . . . International
Palm Beach . . . . . . . . . . International
Pensacola . . . . . . . . . . . NAS
Pensacola . . . . . . . . . . . Regional
Sarasota . . . . . . . . . . . . . Bradenton
Tallahassee . . . . . . . . . . Regional
Whiting . . . . . . . . . . . . . NAS
GEORGIA
Columbus . . . . . . . . . . . Metropolitan
Savannah . . . . . . . . . . . . International
HAWAII
Kahului . . . . . . . . . . . . . Kahului
IDAHO
Boise . . . . . . . . . . . . . . . Air Terminal
ILLINOIS
Champaign . . . . . . . . . . U of Illinois-Willard
Chicago . . . . . . . . . . . . . Midway
Moline . . . . . . . . . . . . . . Quad City
AIM 2/14/08
3-2-7
Controlled Airspace
State/City Airport
Peoria . . . . . . . . . . . . . . Greater Peoria
Springfield . . . . . . . . . . Capital
INDIANA
Evansville . . . . . . . . . . . Regional
Fort Wayne . . . . . . . . . . International
Indianapolis . . . . . . . . . . International
South Bend . . . . . . . . . . Michiana Regional
IOWA
Cedar Rapids . . . . . . . . . The Eastern Iowa
Des Moines . . . . . . . . . . International
KANSAS
Wichita . . . . . . . . . . . . . Mid-Continent
KENTUCKY
Lexington . . . . . . . . . . . Blue Grass
Louisville . . . . . . . . . . . Standiford Field
LOUISIANA
Baton Rouge . . . . . . . . . BTR Metro, Ryan Field
Lafayette . . . . . . . . . . . . Regional
Shreveport . . . . . . . . . . . Barksdale AFB
Shreveport . . . . . . . . . . . Regional
MAINE
Bangor . . . . . . . . . . . . . International
Portland . . . . . . . . . . . . . International Jetport
MICHIGAN
Flint . . . . . . . . . . . . . . . . Bishop International
Grand Rapids . . . . . . . . Kent County International
Lansing . . . . . . . . . . . . . Capital City
MISSISSIPPI
Columbus . . . . . . . . . . . AFB
Jackson . . . . . . . . . . . . . International
MISSOURI
Springfield . . . . . . . . . . Springfield-Branson Regional
MONTANA
Billings . . . . . . . . . . . . . Logan International
NEBRASKA
Lincoln . . . . . . . . . . . . . Municipal
Omaha . . . . . . . . . . . . . . Eppley Airfield
Offutt . . . . . . . . . . . . . . . AFB
NEVADA
Reno . . . . . . . . . . . . . . . Cannon International
NEW HAMPSHIRE
Manchester . . . . . . . . . . Manchester
NEW JERSEY
Atlantic City . . . . . . . . . International
NEW MEXICO
Albuquerque . . . . . . . . . International
NEW YORK
Albany . . . . . . . . . . . . . County
Buffalo . . . . . . . . . . . . . Greater Buffalo International
Islip . . . . . . . . . . . . . . . . Long Island MacArthur
Rochester . . . . . . . . . . . Greater Rochester International
Syracuse . . . . . . . . . . . . Hancock International
State/City Airport
NORTH CAROLINA
Asheville . . . . . . . . . . . Regional
Fayetteville . . . . . . . . . . Regional/Grannis Field
Greensboro . . . . . . . . . . Piedmont Triad International
Pope . . . . . . . . . . . . . . . AFB
Raleigh . . . . . . . . . . . . . Raleigh-Durham International
OHIO
Akron . . . . . . . . . . . . . . Akron-Canton Regional
Columbus . . . . . . . . . . . Port Columbus International
Dayton . . . . . . . . . . . . . James M. Cox International
Toledo . . . . . . . . . . . . . . Express
OKLAHOMA
Oklahoma City . . . . . . . Will Rogers World
Tinker . . . . . . . . . . . . . . AFB
Tulsa . . . . . . . . . . . . . . . International
OREGON
Portland . . . . . . . . . . . . . International
PENNSYLVANIA
Allentown . . . . . . . . . . . Allentown Bethlehem-Easton
PUERTO RICO
San Juan . . . . . . . . . . . . Luis Munoz Marin International
RHODE ISLAND
Providence . . . . . . . . . . Theodore Francis Green State
SOUTH CAROLINA
Charleston . . . . . . . . . . . AFB/International
Columbia . . . . . . . . . . . . Metropolitan
Greer . . . . . . . . . . . . . . . Greenville-Spartanburg
Myrtle Beach . . . . . . . . Myrtle Beach International
Shaw . . . . . . . . . . . . . . . AFB
TENNESSEE
Chattanooga . . . . . . . . . Lovell Field
Knoxville . . . . . . . . . . . McGhee Tyson
Nashville . . . . . . . . . . . . International
TEXAS
Abilene . . . . . . . . . . . . . Regional
Amarillo . . . . . . . . . . . . International
Austin . . . . . . . . . . . . . . Austin-Bergstrom International
Corpus Christi . . . . . . . . International
Dyess . . . . . . . . . . . . . . AFB
El Paso . . . . . . . . . . . . . International
Harlingen . . . . . . . . . . . Rio Grande Valley International
Laughlin . . . . . . . . . . . . AFB
Lubbock . . . . . . . . . . . . International
Midland . . . . . . . . . . . . . International
San Antonio . . . . . . . . . International
VERMONT
Burlington . . . . . . . . . . . International
VIRGIN ISLANDS
St. Thomas . . . . . . . . . . Charlotte Amalie Cyril E. King
AIM 2/14/08
3-2-8 Controlled Airspace
State/City Airport
VIRGINIA
Richmond . . . . . . . . . . . Richard Evelyn Byrd
International
Norfolk . . . . . . . . . . . . . International
Roanoke . . . . . . . . . . . . Regional/Woodrum Field
WASHINGTON
Point Roberts . . . . . . . . Vancouver International
Spokane . . . . . . . . . . . . Fairchild AFB
Spokane . . . . . . . . . . . . International
Whidbey Island . . . . . . . NAS, Ault Field
WEST VIRGINIA
Charleston . . . . . . . . . . . Yeager
WISCONSIN
Green Bay . . . . . . . . . . . Austin Straubel International
Madison . . . . . . . . . . . . Dane County Regional-Traux
Field
Milwaukee . . . . . . . . . . General Mitchell International
3-2-5. Class D Airspace
a. Definition. 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.
b. Operating Rules and Pilot/Equipment
Requirements:
1. Pilot Certification. No specific certifica-
tion required.
2. Equipment. Unless otherwise authorized
by ATC, an operable two-way radio is required.
3. Arrival or Through Flight Entry
Requirements. Two-way radio communication
must be established with the ATC facility providing
ATC services prior to entry and thereafter maintain
those communications while in the Class D airspace.
Pilots of arriving aircraft should contact the control
tower on the publicized frequency and give their
position, altitude, destination, and any request(s).
Radio contact should be initiated far enough from the
Class_D airspace boundary to preclude entering the
Class D airspace before two-way radio communica-
tions are established.
NOTE1. If the controller responds to a radio call with, “[aircraft
callsign] standby,” radio communications have been
established and the pilot can enter the Class D airspace.
2. If workload or traffic conditions prevent immediate
entry into Class D airspace, the controller will inform the
pilot to remain outside the Class D airspace until
conditions permit entry.
EXAMPLE1. “ remain outside the Class Delta
airspace and standby.”
It is important to understand that if the controller responds
to the initial radio call without using the aircraft callsign,
radio communications have not been established and the
pilot may not enter the Class D airspace.
2. “Aircraft calling Manassas tower standby.”
At those airports where the control tower does not operate
24 hours a day, the operating hours of the tower will be
listed on the appropriate charts and in the A/FD. During
the hours the tower is not in operation, the Class E surface
area rules or a combination of Class E rules to 700 feet
above ground level and Class G rules to the surface will
become applicable. Check the A/FD for specifics.
4. Departures from:
(a) A primary or satellite airport with an
operating control tower. Two-way radio communica-
tions must be established and maintained with the
control tower, and thereafter as instructed by ATC
while operating in the Class D airspace.
(b) A satellite airport without an operating
control tower. Two-way radio communications must
be established as soon as practicable after departing
with the ATC facility having jurisdiction over the
Class D airspace as soon as practicable after
departing.
5. Aircraft Speed. Unless otherwise autho-
rized or required by ATC, no person may operate an
aircraft at or below 2,500 feet above the surface
within 4 nautical miles of the primary airport of a
Class D airspace area at an indicated airspeed of more
than 200 knots (230 mph).
c. Class D airspace areas are depicted on Sectional
and Terminal charts with blue segmented lines, and
on IFR En Route Lows with a boxed .
d. Arrival extensions for instrument approach
procedures may be Class D or Class E airspace. As a
general rule, if all extensions are 2 miles or less, they
remain part of the Class D surface area. However, if
any one extension is greater than 2 miles, then all
extensions become Class E.
e. Separation for VFR Aircraft. No separation
services are provided to VFR aircraft.
AIM 2/14/08
3-2-9
Controlled Airspace
3-2-6. Class E Airspace
a. Definition. 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.
b. Operating Rules and Pilot/Equipment
Requirements:
1. Pilot Certification. No specific certifica-
tion required.
2. Equipment. No specific equipment
required by the airspace.
3. Arrival or Through Flight Entry Require-
ments. No specific requirements.
c. Charts. Class E airspace below 14,500 feet
MSL is charted on Sectional, Terminal, and IFR
Enroute Low Altitude charts.
d. Vertical limits. Except for 18,000 feet MSL,
Class E airspace has no defined vertical limit but
rather it extends upward from either the surface or a
designated altitude to the overlying or adjacent
controlled airspace.
e. Types of Class E Airspace:
1. Surface area designated for an air-
port. When designated as a surface area for an
airport, the airspace will be configured to contain all
instrument procedures.
2. Extension to a surface area. There are
Class_E airspace areas that serve as extensions to
Class B, Class_C, and Class D surface areas
designated for an airport. Such airspace provides
controlled airspace to contain standard instrument
approach procedures without imposing a commu-
nications requirement on pilots operating under VFR.
3. Airspace used for transition. There are
Class_E airspace areas beginning at either 700 or
1,200 feet AGL used to transition to/from the
terminal or en route environment.
4. En Route Domestic Areas. There are
Class_E airspace areas that extend upward from a
specified altitude and are en route domestic airspace
areas that provide controlled airspace in those areas
where there is a requirement to provide IFR en route
ATC services but the Federal airway system is
inadequate.
5. Federal Airways. The Federal airways are
Class E airspace areas and, unless otherwise
specified, extend upward from 1,200 feet to, but not
including, 18,000 feet MSL. The colored airways are
green, red, amber, and blue. The VOR airways are
classified as Domestic, Alaskan, and Hawaiian.
6. Offshore Airspace Areas. There are
Class_E airspace areas that extend upward from a
specified altitude to, but not including, 18,000 feet
MSL and are designated as offshore airspace areas.
These areas provide controlled airspace beyond
12_miles from the coast of the U.S. in those areas
where there is a requirement to provide IFR en route
ATC services and within which the U.S. is applying
domestic procedures.
7. Unless designated at a lower altitude, Class E
airspace begins at 14,500 feet MSL to, but not
including, 18,000 feet MSL overlying: the 48_contig-
uous States including the waters within 12 miles from
the coast of the 48 contiguous States; the District of
Columbia; Alaska, including the waters within
12_miles from the coast of Alaska, and that airspace
above FL_600; excluding the Alaska peninsula west
of long._160 _00'00''W, and the airspace below
1,500_feet above the surface of the earth unless
specifically so designated.
f. Separation for VFR Aircraft. No separation
services are provided to VFR aircraft.
AIM 2/14/08
3-3-1
Class G Airspace
Section 3. Class G Airspace
3-3-1. General
Class G airspace (uncontrolled) is that portion of
airspace that has not been designated as Class A,
Class_B, Class C, Class D, or Class E airspace.
3-3-2. VFR Requirements
Rules governing VFR flight have been adopted to
assist the pilot in meeting the responsibility to see and
avoid other aircraft. Minimum flight visibility and
distance from clouds required for VFR flight are
contained in 14_CFR Section 91.155.
(See TBL 3-1-1.)
3-3-3. IFR Requirements
a. Title 14 CFR specifies the pilot and aircraft
equipment requirements for IFR flight. Pilots are
reminded that in addition to altitude or flight level
requirements, 14 CFR Section 91.177 includes a
requirement to remain at least 1,000 feet (2,000 feet
in designated mountainous terrain) above the highest
obstacle within a horizontal distance of 4 nautical
miles from the course to be flown.
b. IFR Altitudes.
(See TBL 3-3-1.)
TBL 3-3-1
IFR Altitudes
Class G Airspace
If your magnetic course
(ground track) is:
And you are below
18,000 feet MSL, fly:
0_ to 179_ Odd thousands MSL, (3,000; 5,000; 7,000, etc.)
180_ to 359_ Even thousands MSL, (2,000; 4,000; 6,000, etc.)
AIM 2/14/08
3-4-1
Special Use Airspace
Section 4. Special Use Airspace
3-4-1. General
a. Special use airspace consists of that airspace
wherein activities must be confined because of their
nature, or wherein limitations are imposed upon
aircraft operations that are not a part of those
activities, or both. Except for controlled firing areas,
special use airspace areas are depicted on aeronauti-
cal charts.
b. Prohibited and restricted areas are regulatory
special use airspace and are established in 14 CFR
Part_73 through the rulemaking process.
c. Warning areas, military operations areas
(MOAs), alert areas, and controlled firing areas
(CFAs) are nonregulatory special use airspace.
d. Special use airspace descriptions (except CFAs)
are contained in FAA Order JO 7400.8, Special Use
Airspace.
e. Special use airspace (except CFAs) are charted
on IFR or visual charts and include the hours of
operation, altitudes, and the controlling agency.
3-4-2. Prohibited Areas
Prohibited areas contain airspace of defined
dimensions identified by an area on the surface of the
earth within which the flight of aircraft is prohibited.
Such areas are established for security or other
reasons associated with the national welfare. These
areas are published in the Federal Register and are
depicted on aeronautical charts.
3-4-3. Restricted Areas
a. Restricted areas contain airspace identified by
an area on the surface of the earth 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 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 such as artillery firing, aerial
gunnery, or guided missiles. Penetration of restricted
areas without authorization from the using or
controlling agency may be extremely hazardous to
the aircraft and its occupants. Restricted areas are
published in the Federal Register and constitute
14_CFR Part 73.
b. ATC facilities apply the following procedures
when aircraft are operating on an IFR clearance
(including those cleared by ATC to maintain
VFR-on-top) via a route which lies within joint-use
restricted airspace.
1. If the restricted area is not active and has been
released to the controlling agency (FAA), the ATC
facility will allow the aircraft to operate in the
restricted airspace without issuing specific clearance
for it to do so.
2. If the restricted area is active and has not been
released to the controlling agency (FAA), the ATC
facility will issue a clearance which will ensure the
aircraft avoids the restricted airspace unless it is on an
approved altitude reservation mission or has obtained
its own permission to operate in the airspace and so
informs the controlling facility.
NOTE-
The above apply only to joint-use restricted airspace and
not to prohibited and nonjoint-use airspace. For the latter
categories, the ATC facility will issue a clearance so the
aircraft will avoid the restricted airspace unless it is on an
approved altitude reservation mission or has obtained its
own permission to operate in the airspace and so informs
the controlling facility.
c. Restricted airspace is depicted on the en route
chart appropriate for use at the altitude or flight level
being flown. For joint-use restricted areas, the name
of the controlling agency is shown on these charts.
For all prohibited areas and nonjoint-use restricted
areas, unless otherwise requested by the using
agency, the phrase “NO A/G” is shown.
3-4-4. Warning Areas
A warning area is airspace of defined dimensions,
extending from three nautical miles outward from the
coast of the U.S., that contains activity that may be
hazardous to nonparticipating aircraft. The purpose
of such warning areas is to warn nonparticipating
pilots of the potential danger. A warning area may be
located over domestic or international waters or both.
AIM 2/14/08
3-4-2 Special Use Airspace
3-4-5. Military Operations Areas
a. MOAs consist of airspace of defined vertical
and lateral limits established for the purpose of
separating certain military training activities from
IFR traffic. Whenever a MOA is being used,
nonparticipating IFR traffic may be cleared through
a MOA if IFR separation can be provided by ATC.
Otherwise, ATC will reroute or restrict nonparticipat-
ing IFR traffic.
b. Examples of activities conducted in MOAs
include, but are not limited to: air combat tactics, air
intercepts, aerobatics, formation training, and
low-altitude tactics. Military pilots flying in an active
MOA are exempted from the provisions of 14 CFR
Section 91.303(c) and (d) which prohibits aerobatic
flight within Class D and Class E surface areas, and
within Federal airways. Additionally, the Department
of Defense has been issued an authorization to
operate aircraft at indicated airspeeds in excess of
250_knots below 10,000 feet MSL within active
MOAs.
c. Pilots operating under VFR should exercise
extreme caution while flying within a MOA when
military activity is being conducted. The activity
status (active/inactive) of MOAs may change
frequently. Therefore, pilots should contact any FSS
within 100 miles of the area to obtain accurate
real-time information concerning the MOA hours of
operation. Prior to entering an active MOA, pilots
should contact the controlling agency for traffic
advisories.
d. MOAs are depicted on sectional, VFR Terminal
Area, and Enroute Low Altitude charts.
3-4-6. Alert Areas
Alert areas are depicted on aeronautical charts to
inform nonparticipating pilots of areas that may
contain a high volume of pilot training or an unusual
type of aerial activity. Pilots should be particularly
alert when flying in these areas. All activity within an
alert area shall be conducted in accordance with
CFRs, without waiver, and pilots of participating
aircraft as well as pilots transiting the area shall be
equally responsible for collision avoidance.
3-4-7. Controlled Firing Areas
CFAs contain activities which, if not conducted in a
controlled environment, could be hazardous to
nonparticipating aircraft. The distinguishing feature
of the CFA, as compared to other special use airspace,
is that its activities are suspended immediately when
spotter aircraft, radar, or ground lookout positions
indicate an aircraft might be approaching the area.
There is no need to chart CFAs since they do not cause
a nonparticipating aircraft to change its flight path.
AIM 2/14/08
3-5-1
Other Airspace Areas
Section 5. Other Airspace Areas
3-5-1. Airport Advisory/Information
Services
a. There are three advisory type services available
at selected airports.
1. Local Airport Advisory (LAA) service is
operated within 10 statute miles of an airport where
a control tower is not operating but where a FSS is
located on the airport. At such locations, the FSS
provides a complete local airport advisory service to
arriving and departing aircraft. During periods of fast
changing weather the FSS will automatically provide
Final Guard as part of the service from the time the
aircraft reports “on-final” or “taking-the-activerunway” until the aircraft reports “on-the-ground” or
“airborne.”
NOTE-
Current policy, when requesting remote ATC services,
requires that a pilot monitor the automated weather
broadcast at the landing airport prior to requesting ATC
services. The FSS automatically provides Final Guard,
when appropriate, during LAA/Remote Airport Advisory
(RAA) operations. Final Guard is a value added
wind/altimeter monitoring service, which provides an
automatic wind and altimeter check during active weather
situations when the pilot reports on-final or taking the
active runway. During the landing or take-off operation
when the winds or altimeter are actively changing the FSS
will blind broadcast significant changes when the
specialist believes the change might affect the operation.
Pilots should acknowledge the first wind/altimeter check
but due to cockpit activity no acknowledgement is expected
for the blind broadcasts. It is prudent for a pilot to report
on-the-ground or airborne to end the service.
2. RAA service is operated within 10 statute
miles of specified high activity GA airports where a
control tower is not operating. Airports offering this
service are listed in the A/FD and the published
service hours may be changed by NOTAM D. Final
Guard is automatically provided with RAA.
3. Remote Airport Information Service (RAIS)
is provided in support of short term special events like
small to medium fly-ins. The service is advertised by
NOTAM D only. The FSS will not have access to a
continuous readout of the current winds and
altimeter; therefore, RAIS does not include weather
and/or Final Guard service. However, known traffic,
special event instructions, and all other services are
provided.
NOTE-
The airport authority and/or manager should request RAIS
support on official letterhead directly with the manager of
the FSS that will provide the service at least 60 days in
advance. Approval authority rests with the FSS manager
and is based on workload and resource availability.
REFERENCE-
AIM, Traffic Advisory Practices at Airports Without Operating Control
Towers, Paragraph 4-1-9.
b. It is not mandatory that pilots participate in the
Airport Advisory programs. Participation enhances
safety for everyone operating around busy GA
airports; therefore, everyone is encouraged to
participate and provide feedback that will help
improve the program.
3-5-2. Military Training Routes
a. National security depends largely on the
deterrent effect of our airborne military forces. To be
proficient, the military services must train in a wide
range of airborne tactics. One phase of this training
involves “low level” combat tactics. The required
maneuvers and high speeds are such that they may
occasionally make the see-and-avoid aspect of VFR
flight more difficult without increased vigilance in
areas containing such operations. In an effort to
ensure the greatest practical level of safety for all
flight operations, the Military Training Route (MTR)
program was conceived.
b. The MTR program is a joint venture by the FAA
and the Department of Defense (DOD). MTRs are
mutually developed for use by the military for the
purpose of conducting low-altitude, high-speed
training. The routes above 1,500 feet AGL are
developed to be flown, to the maximum extent
possible, under IFR. The routes at 1,500 feet AGL
and below are generally developed to be flown under
VFR.
AIM 2/14/08
3-5-2 Other Airspace Areas
c. Generally, MTRs are established below
10,000_feet MSL for operations at speeds in excess of
250 knots. However, route segments may be defined
at higher altitudes for purposes of route continuity.
For example, route segments may be defined for
descent, climbout, and mountainous terrain. There
are IFR and VFR routes as follows:
1. IFR Military Training Routes-(IR).
Operations on these routes are conducted in
accordance with IFR regardless of weather
conditions.
2. VFR Military Training Routes-(VR).
Operations on these routes are conducted in
accordance with VFR except flight visibility shall be
5 miles or more; and flights shall not be conducted
below a ceiling of less than 3,000 feet AGL.
d. Military training routes will be identified and
charted as follows:
1. Route identification.
(a) MTRs with no segment above 1,500 feet
AGL shall be identified by four number characters;
e.g., IR1206, VR1207.
(b) MTRs that include one or more segments
above 1,500 feet AGL shall be identified by three
number characters; e.g., IR206, VR207.
(c) Alternate IR/VR routes or route segments
are identified by using the basic/principal route
designation followed by a letter suffix, e.g., IR008A,
VR1007B, etc.
2. Route charting.
(a) IFR Low Altitude En Route Chart. This
chart will depict all IR routes and all VR routes that
accommodate operations above 1,500 feet AGL.
(b) VFR Sectional Charts. These charts
will depict military training activities such as IR, VR,
MOA, Restricted Area, Warning Area, and Alert
Area information.
(c) Area Planning (AP/1B) Chart (DOD
Flight Information Publication-FLIP). This chart
is published by the DOD primarily for military users
and contains detailed information on both IR and VR
routes.
REFERENCE-
AIM, National Imagery and Mapping Agency (NIMA) Products,
Paragraph 9-1-5, Subparagraph a.
e. The FLIP contains charts and narrative
descriptions of these routes. This publication is
available to the general public by single copy or
annual subscription from:
National Aeronautical Charting Office (NACO)
Distribution Division
Federal Aviation Administration
6501 Lafayette Avenue
Riverdale, MD 20737-1199
Toll free phone: 1-800-638-8972
Commercial: 301-436-8301
This DOD FLIP is available for pilot briefings at FSS
and many airports.
f. Nonparticipating aircraft are not prohibited
from flying within an MTR; however, extreme
vigilance should be exercised when conducting flight
through or near these routes. Pilots should contact
FSSs within 100 NM of a particular MTR to obtain
current information or route usage in their vicinity.
Information available includes times of scheduled
activity, altitudes in use on each route segment, and
actual route width. Route width varies for each MTR
and can extend several miles on either side of the
charted MTR centerline. Route width information for
IR and VR MTRs is also available in the FLIP AP/1B
along with additional MTR (slow routes/air refueling
routes) information. When requesting MTR informa-
tion, pilots should give the FSS their position, route
of flight, and destination in order to reduce frequency
congestion and permit the FSS specialist to identify
the MTR which could be a factor.
3-5-3. Temporary Flight Restrictions
a. General. This paragraph describes the types of
conditions under which the FAA may impose
temporary flight restrictions. It also explains which
FAA elements have been delegated authority to issue
a temporary flight restrictions NOTAM and lists the
types of responsible agencies/offices from which the
FAA will accept requests to establish temporary
flight restrictions. The 14 CFR is explicit as to what
operations are prohibited, restricted, or allowed in a
temporary flight restrictions area. Pilots are responsi-
ble to comply with 14 CFR Sections 91.137, 91.138,
91.141 and 91.143 when conducting flight in an area
where a temporary flight restrictions area is in effect,
and should check appropriate NOTAMs during flight
planning.
AIM 2/14/08
3-5-3
Other Airspace Areas
b. The purpose for establishing a temporary
flight restrictions area is to:
1. Protect persons and property in the air or on
the surface from an existing or imminent hazard
associated with an incident on the surface when the
presence of low flying aircraft would magnify, alter,
spread, or compound that hazard (14 CFR
Section_91.137(a)(1));
2. Provide a safe environment for the operation
of disaster relief aircraft (14 CFR Sec-
tion_91.137(a)(2)); or
3. Prevent an unsafe congestion of sightseeing
aircraft above an incident or event which may
generate a high degree of public interest (14 CFR
Section_91.137(a)(3)).
4. Protect declared national disasters for
humanitarian reasons in the State of Hawaii (14 CFR
Section_91.138).
5. Protect the President, Vice President, or other
public figures (14 CFR Section 91.141).
6. Provide a safe environment for space agency
operations (14 CFR Section 91.143).
c. Except for hijacking situations, when the
provisions of 14 CFR Section 91.137(a)(1) or (a)(2)
are necessary, a temporary flight restrictions area will
only be established by or through the area manager at
the Air Route Traffic Control Center (ARTCC)
having jurisdiction over the area concerned. A
temporary flight restrictions NOTAM involving the
conditions of 14_CFR Section 91.137(a)(3) will be
issued at the direction of the service area office
director having oversight of the airspace concerned.
When hijacking situations are involved, a temporary
flight restrictions area will be implemented through
the TSA Aviation Command Center. The appropriate
FAA air traffic element, upon receipt of such a
request, will establish a temporary flight restrictions
area under 14_CFR Section_91.137(a)(1).
d. The FAA accepts recommendations for the
establishment of a temporary flight restrictions area
under 14_CFR Section 91.137(a)(1) from military
major command headquarters, regional directors of
the Office of Emergency Planning, Civil Defense
State Directors, State Governors, or other similar
authority. For the situations involving 14 CFR
Section 91.137(a)(2), the FAA accepts recommenda-
tions from military commanders serving as regional,
subregional, or Search and Rescue (SAR) coordina-
tors; by military commanders directing or
coordinating air operations associated with disaster
relief; or by civil authorities directing or coordinating
organized relief air operations (includes representa-
tives of the Office of Emergency Planning, U.S.
Forest Service, and State aeronautical agencies).
Appropriate authorities for a temporary flight
restrictions establishment under 14 CFR
Section_91.137(a)(3) are any of those listed above or
by State, county, or city government entities.
e. The type of restrictions issued will be kept to a
minimum by the FAA consistent with achievement of
the necessary objective. Situations which warrant the
extreme restrictions of 14 CFR Section 91.137(a)(1)
include, but are not limited to: toxic gas leaks or
spills, flammable agents, or fumes which if fanned by
rotor or propeller wash could endanger persons or
property on the surface, or if entered by an aircraft
could endanger persons or property in the air;
imminent volcano eruptions which could endanger
airborne aircraft and occupants; nuclear accident or
incident; and hijackings. Situations which warrant
the restrictions associated with 14 CFR Sec-
tion_91.137(a)(2) include: forest fires which are
being fought by releasing fire retardants from
aircraft; and aircraft relief activities following a
disaster (earthquake, tidal wave, flood, etc.). 14 CFR
Section_91.137(a)(3) restrictions are established for
events and incidents that would attract an unsafe
congestion of sightseeing aircraft.
f. The amount of airspace needed to protect
persons and property or provide a safe environment
for rescue/relief aircraft operations is normally
limited to within 2,000 feet above the surface and
within a 3-nautical-mile radius. Incidents occurring
within Class B, Class C, or Class D airspace will
normally be handled through existing procedures and
should not require the issuance of a temporary flight
restrictions NOTAM. Temporary flight restrictions
affecting airspace outside of the U.S. and its
territories and possessions are issued with verbiage
excluding that airspace outside of the 12-mile coastal
limits.
AIM 2/14/08
3-5-4 Other Airspace Areas
g. The FSS nearest the incident site is normally the
“coordination facility.” When FAA communications
assistance is required, the designated FSS will
function as the primary communications facility for
coordination between emergency control authorities
and affected aircraft. The ARTCC may act as liaison
for the emergency control authorities if adequate
communications cannot be established between the
designated FSS and the relief organization. For
example, the coordination facility may relay
authorizations from the on-scene emergency re-
sponse official in cases where news media aircraft
operations are approved at the altitudes used by relief
aircraft.
h. ATC may authorize operations in a temporary
flight restrictions area under its own authority only
when flight restrictions are established under 14 CFR
Section 91.137(a)(2) and (a)(3). The appropriate
ARTCC/airport traffic control tower manager will,
however, ensure that such authorized flights do not
hamper activities or interfere with the event for which
restrictions were implemented. However, ATC will
not authorize local IFR flights into the temporary
flight restrictions area.
i. To preclude misunderstanding, the implement-
ing NOTAM will contain specific and formatted
information. The facility establishing a temporary
flight restrictions area will format a NOTAM
beginning with the phrase “FLIGHT RESTRIC-
TIONS” followed by: the location of the temporary
flight restrictions area; the effective period; the area
defined in statute miles; the altitudes affected; the
FAA coordination facility and commercial telephone
number; the reason for the temporary flight
restrictions; the agency directing any relief activities
and its commercial telephone number; and other
information considered appropriate by the issuing
authority.
EXAMPLE1. 14 CFR Section 91.137(a)(1):
The following NOTAM prohibits all aircraft operations
except those specified in the NOTAM.
Flight restrictions Matthews, Virginia, effective immedi-
ately until 9610211200. Pursuant to 14 CFR
Section_91.137(a)(1) temporary flight restrictions are in
effect. Rescue operations in progress. Only relief aircraft
operations under the direction of the Department of
Defense are authorized in the airspace at and below
5,000_feet MSL within a 2-nautical-mile radius of Laser
AFB, Matthews, Virginia. Commander, Laser AFB, in
charge (897) 946-5543 (122.4). Steenson FSS
(792)_555-6141 (123.1) is the FAA coordination facility.
2. 14 CFR Section 91.137(a)(2):
The following NOTAM permits flight operations in
accordance with 14 CFR Section 91.137(a)(2). The on-site
emergency response official to authorize media aircraft
operations below the altitudes used by the relief aircraft.
Flight restrictions 25 miles east of Bransome, Idaho,
effective immediately until 9601202359 UTC. Pursuant to
14 CFR Section 91.137(a)(2) temporary flight restrictions
are in effect within a 4-nautical-mile radius of the
intersection of county roads 564 and 315 at and below
3,500 feet MSL to provide a safe environment for fire
fighting aircraft operations. Davis County sheriff 's
department (792) 555-8122 (122.9) is in charge of
on-scene emergency response activities. Glivings FSS
(792) 555-1618 (122.2) is the FAA coordination facility.
3. 14 CFR Section 91.137(a)(3):
The following NOTAM prohibits sightseeing aircraft
operations.
Flight restrictions Brown, Tennessee, due to olympic
activity. Effective 9606181100 UTC until 9607190200
UTC. Pursuant to 14 CFR Section 91.137(a)(3) temporary
flight restrictions are in effect within a 3-nautical-mile
radius of N355783/W835242 and Volunteer VORTAC 019
degree radial 3.7 DME fix at and below 2,500 feet MSL.
Norton FSS (423) 555-6742 (126.6) is the FAA
coordination facility.
4. 14 CFR Section 91.138:
The following NOTAM prohibits all aircraft except those
operating under the authorization of the official in charge
of associated emergency or disaster relief response
activities, aircraft carrying law enforcement officials,
aircraft carrying personnel involved in an emergency or
legitimate scientific purposes, carrying properly accred-
ited news media, and aircraft operating in accordance with
an ATC clearance or instruction.
Flight restrictions Kapalua, Hawaii, effective 9605101200
UTC until 9605151500 UTC. Pursuant to 14_CFR
Section_91.138 temporary flight restrictions are in effect
within a 3-nautical-mile radius of N205778/W1564038
and Maui/OGG/VORTAC 275_degree radial at 14.1
nautical miles. John Doe 808-757-4469 or 122.4 is in
charge of the operation. Honolulu/HNL 808-757-4470
(123.6) AFSS is the FAA coordination facility.
5. 14 CFR Section 91.141:
The following NOTAM prohibits all aircraft.
Flight restrictions Stillwater, Oklahoma, June 21, 1996.
Pursuant to 14 CFR Section 91.141 aircraft flight
operations are prohibited within a 3-nautical-mile radius,
AIM 2/14/08
3-5-5
Other Airspace Areas
below 2000 feet AGL of N360962/W970515 and the
Stillwater/SWO/VOR/DME 176 degree radial 3.8-nauti-
cal-mile fix from 1400 local time to 1700 local time
June_21, 1996, unless otherwise authorized by ATC.
6. 14 CFR Section 91.143:
The following NOTAM prohibits any aircraft of U.S.
registry, or pilot any aircraft under the authority of an
airman certificate issued by the FAA.
Kennedy space center space operations area effective
immediately until 9610152100 UTC. Pursuant to 14 CFR
Section 91.143, flight operations conducted by FAA
certificated pilots or conducted in aircraft of U.S. registry
are prohibited at any altitude from surface to unlimited,
within the following area 30-nautical-mile radius of the
Melbourne/MLB/VORTAC 010 degree radial 21-nauti-
cal-mile fix. St. Petersburg, Florida/PIE/AFSS
813-545-1645 (122.2) is the FAA coordination facility and
should be contacted for the current status of any airspace
associated with the space shuttle operations. This airspace
encompasses R2933, R2932, R2931, R2934, R2935,
W497A and W158A. Additional warning and restricted
areas will be active in conjunction with the operations.
Pilots shall consult all NOTAMs regarding this operation.
3-5-4. Parachute Jump Aircraft Operations
a. Procedures relating to parachute jump areas are
contained in 14 CFR Part 105. Tabulations of
parachute jump areas in the U.S. are contained in the
A/FD.
b. Pilots of aircraft engaged in parachute jump
operations are reminded that all reported altitudes
must be with reference to mean sea level, or flight
level, as appropriate, to enable ATC to provide
meaningful traffic information.
c. Parachute operations in the vicinity of an airport
without an operating control tower - there is no
substitute for alertness while in the vicinity of an
airport. It is essential that pilots conducting parachute
operations be alert, look for other traffic, and
exchange traffic information as recommended in
paragraph_4-1-9, Traffic Advisory Practices at
Airports Without Operating Control Towers. In
addition, pilots should avoid releasing parachutes
while in an airport traffic pattern when there are other
aircraft in that pattern. Pilots should make
appropriate broadcasts on the designated Common
Traffic Advisory Frequency (CTAF), and monitor
that CTAF until all parachute activity has terminated
or the aircraft has left the area. Prior to commencing
a jump operation, the pilot should broadcast the
aircraft's altitude and position in relation to the
airport, the approximate relative time when the jump
will commence and terminate, and listen to the
position reports of other aircraft in the area.
3-5-5. Published VFR Routes
Published VFR routes for transitioning around, under
and through complex airspace such as Class B
airspace were developed through a number of FAA
and industry initiatives. All of the following terms,
i.e., “VFR Flyway” “VFR Corridor” and “Class B
Airspace VFR Transition Route” have been used
when referring to the same or different types of routes
or airspace. The following paragraphs identify and
clarify the functionality of each type of route, and
specify where and when an ATC clearance is
required.
a. VFR Flyways.
1. VFR Flyways and their associated Flyway
Planning Charts were developed from the recommen-
dations of a National Airspace Review Task Group.
A VFR Flyway is defined as a general flight path not
defined as a specific course, for use by pilots in
planning flights into, out of, through or near complex
terminal airspace to avoid Class B airspace. An ATC
clearance is NOT required to fly these routes.
AIM 2/14/08
3-5-6 Other Airspace Areas
FIG 3-5-1
VFR Flyway Planning Chart
AIM 2/14/08
3-5-7
Other Airspace Areas
2. VFR Flyways are depicted on the reverse side
of some of the VFR Terminal Area Charts (TAC),
commonly referred to as Class B airspace charts. (See
FIG 3-5-1.) Eventually all TACs will include a VFR
Flyway Planning Chart. These charts identify VFR
flyways designed to help VFR pilots avoid major
controlled traffic flows. They may further depict
multiple VFR routings throughout the area which
may be used as an alternative to flight within Class B
airspace. The ground references provide a guide for
improved visual navigation. These routes are not
intended to discourage requests for VFR operations
within Class B airspace but are designed solely to
assist pilots in planning for flights under and around
busy Class B airspace without actually entering
Class__B airspace.
3. It is very important to remember that these
suggested routes are not sterile of other traffic. The
entire Class B airspace, and the airspace underneath
it, may be heavily congested with many different
types of aircraft. Pilot adherence to VFR rules must
be exercised at all times. Further, when operating
beneath Class B airspace, communications must be
established and maintained between your aircraft and
any control tower while transiting the Class B,
Class_C, and Class D surface areas of those airports
under Class B airspace.
b. VFR Corridors.
1. The design of a few of the first Class B
airspace areas provided a corridor for the passage of
uncontrolled traffic. A VFR corridor is defined as
airspace through Class B airspace, with defined
vertical and lateral boundaries, in which aircraft may
operate without an ATC clearance or communication
with air traffic control.
2. These corridors are, in effect, a “hole”
through Class B airspace. (See FIG 3-5-2.) A classic
example would be the corridor through the Los
Angeles Class B airspace, which has been subse-
quently changed to Special Flight Rules airspace
(SFR). A corridor is surrounded on all sides by
Class_B airspace and does not extend down to the
surface like a VFR Flyway. Because of their finite
lateral and vertical limits, and the volume of VFR
traffic using a corridor, extreme caution and vigilance
must be exercised.
FIG 3-5-2
Class B Airspace
3. Because of the heavy traffic volume and the
procedures necessary to efficiently manage the flow
of traffic, it has not been possible to incorporate VFR
corridors in the development or modifications of
Class_B airspace in recent years.
c. Class B Airspace VFR Transition Routes.
1. To accommodate VFR traffic through certain
Class B airspace, such as Seattle, Phoenix and
Los_Angeles, Class B Airspace VFR Transition
Routes were developed. A Class B Airspace VFR
Transition Route is defined as a specific flight course
depicted on a TAC for transiting a specific Class B
airspace. These routes include specific ATC-assigned
altitudes, and pilots must obtain an ATC clearance
prior to entering Class B airspace on the route.
2. These routes, as depicted in FIG 3-5-3, are
designed to show the pilot where to position the
aircraft outside of, or clear of, the Class B airspace
where an ATC clearance can normally be expected
with minimal or no delay. Until ATC authorization is
received, pilots must remain clear of Class B
airspace. On initial contact, pilots should advise ATC
of their position, altitude, route name desired, and
direction of flight. After a clearance is received, pilots
must fly the route as depicted and, most importantly,
adhere to ATC instructions.
AIM 2/14/08
3-5-8 Other Airspace Areas
FIG 3-5-3
VFR Transition Route
AIM 2/14/08
3-5-9
Other Airspace Areas
3-5-6. Terminal Radar Service Area (TRSA)
a. Background. TRSAs were originally estab-
lished as part of the Terminal Radar Program at
selected airports. TRSAs were never controlled
airspace from a regulatory standpoint because the
establishment of TRSAs was never subject to the
rulemaking process; consequently, TRSAs are not
contained in 14 CFR Part_71 nor are there any TRSA
operating rules in 14_CFR Part 91. Part of the Airport
Radar Service Area (ARSA) program was to
eventually replace all TRSAs. However, the ARSA
requirements became relatively stringent and it was
subsequently decided that TRSAs would have to
meet ARSA criteria before they would be converted.
TRSAs do not fit into any of the U.S. airspace classes;
therefore, they will continue to be non-Part_71
airspace areas where participating pilots can receive
additional radar services which have been redefined
as TRSA Service.
b. TRSAs. The primary airport(s) within the
TRSA become(s) Class D airspace. The remaining
portion of the TRSA overlies other controlled
airspace which is normally Class E airspace
beginning at 700 or 1,200 feet and established to
transition to/from the en route/terminal environment.
c. Participation. Pilots operating under VFR are
encouraged to contact the radar approach control and
avail themselves of the TRSA Services. However,
participation is voluntary on the part of the pilot. See
Chapter 4, Air Traffic Control, for details and
procedures.
d. Charts. TRSAs are depicted on VFR sectional
and terminal area charts with a solid black line and
altitudes for each segment. The Class D portion is
charted with a blue segmented line.
3-5-7. National Security Areas
National Security Areas consist of airspace of defined
vertical and lateral dimensions established at
locations where there is a requirement for increased
security and safety of ground facilities. Pilots are
requested to voluntarily avoid flying through the
depicted NSA. When it is necessary to provide a
greater level of security and safety, flight in NSAs
may be temporarily prohibited by regulation under
the provisions of 14_CFR Section 99.7. Regulatory
prohibitions will be issued by System Operations,
System Operations Airspace and AIM Office,
Airspace and Rules, and disseminated via NOTAM.
Inquiries about NSAs should be directed to Airspace
and Rules.
AIM 2/14/08
4-1-1
Services Available to Pilots
Chapter 4. Air Traffic Control
Section 1. Services Available to Pilots
4-1-1. Air Route Traffic Control Centers
Centers are established primarily to provide air traffic
service to aircraft operating on IFR flight plans within
controlled airspace, and principally during the
en_route phase of flight.
4-1-2. Control Towers
Towers have been established to provide for a safe,
orderly and expeditious flow of traffic on and in the
vicinity of an airport. When the responsibility has
been so delegated, towers also provide for the
separation of IFR aircraft in the terminal areas.
REFERENCE-
AIM, Approach Control, Paragraph 5-4-3.
4-1-3. Flight Service Stations
a. Flight Service Stations (FSSs) are air traffic
facilities which provide pilot briefings, en route
communications and VFR search and rescue
services, assist lost aircraft and aircraft in emergency
situations, relay ATC clearances, originate Notices to
Airmen, broadcast aviation weather and National
Airspace System (NAS) information, receive and
process IFR flight plans, and monitor navigational
aids (NAVAIDs). In addition, at selected locations
FSSs provide En Route Flight Advisory Service
(Flight Watch), take weather observations, issue
airport advisories, and advise Customs and Immigra-
tion of transborder flights.
b. Supplemental Weather Service Locations
(SWSLs) are airport facilities staffed with contract
personnel who take weather observations and provide
current local weather to pilots via telephone or radio.
All other services are provided by the parent FSS.
4-1-4. Recording and Monitoring
a. Calls to air traffic control (ATC) facilities
(ARTCCs, Towers, FSSs, Central Flow, and
Operations Centers) over radio and ATC operational
telephone lines (lines used for operational purposes
such as controller instructions, briefings, opening and
closing flight plans, issuance of IFR clearances and
amendments, counter hijacking activities, etc.) may
be monitored and recorded for operational uses such
as accident investigations, accident prevention,
search and rescue purposes, specialist training and
evaluation, and technical evaluation and repair of
control and communications systems.
b. Where the public access telephone is recorded,
a beeper tone is not required. In place of the “beep”
tone the FCC has substituted a mandatory require-
ment that persons to be recorded be given notice they
are to be recorded and give consent. Notice is given
by this entry, consent to record is assumed by the
individual placing a call to the operational facility.
4-1-5. Communications Release of IFR
Aircraft Landing at an Airport Without an
Operating Control Tower
Aircraft operating on an IFR flight plan, landing at an
airport without an operating control tower will be
advised to change to the airport advisory frequency
when direct communications with ATC are no longer
required. Towers and centers do not have nontower
airport traffic and runway in use information. The
instrument approach may not be aligned with the
runway in use; therefore, if the information has not
already been obtained, pilots should make an
expeditious change to the airport advisory frequency
when authorized.
REFERENCE-
AIM, Advance Information on Instrument Approach, Paragraph 5-4-4.
4-1-6. Pilot Visits to Air Traffic Facilities
Pilots are encouraged to visit air traffic facilities
(Towers, Centers and FSSs) and familiarize them-
selves with the ATC system. On rare occasions,
facilities may not be able to approve a visit because
of ATC workload or other reasons. It is, therefore,
requested that pilots contact the facility prior to the
visit and advise of the number of persons in the group,
the time and date of the proposed visit and the primary
interest of the group. With this information available,
the facility can prepare an itinerary and have someone
available to guide the group through the facility.
AIM 2/14/08
4-1-2 Services Available to Pilots
4-1-7. Operation Take-off and Operation
Raincheck
Operation Take-off is a program that educates pilots
in how best to utilize the FSS modernization efforts
and services available in Automated Flight Service
Stations (AFSS), as stated in FAA Order 7230.17,
Pilot Education Program - Operation Takeoff.
Operation Raincheck is a program designed to
familiarize pilots with the ATC system, its functions,
responsibilities and benefits.
4-1-8. Approach Control Service for VFR
Arriving Aircraft
a. Numerous approach control facilities have
established programs for arriving VFR aircraft to
contact approach control for landing information.
This information includes: wind, runway, and
altimeter setting at the airport of intended landing.
This information may be omitted if contained in the
Automatic Terminal Information Service (ATIS)
broadcast and the pilot states the appropriate ATIS
code.
NOTE-
Pilot use of “have numbers” does not indicate receipt of the
ATIS broadcast. In addition, the controller will provide
traffic advisories on a workload permitting basis.
b. Such information will be furnished upon initial
contact with concerned approach control facility. The
pilot will be requested to change to the tower
frequency at a predetermined time or point, to receive
further landing information.
c. Where available, use of this procedure will not
hinder the operation of VFR flights by requiring
excessive spacing between aircraft or devious
routing.
d. Compliance with this procedure is not
mandatory but pilot participation is encouraged.
REFERENCE-
AIM, Terminal Radar Services for VFR Aircraft, Paragraph 4-1-17.
NOTE-
Approach control services for VFR aircraft are normally
dependent on ATC radar. These services are not available
during periods of a radar outage. Approach control
services for VFR aircraft are limited when CENRAP is in
use.
4-1-9. Traffic Advisory Practices at
Airports Without Operating Control Towers
(See TBL 4-1-1.)
a. Airport Operations Without Operating
Control Tower
1. There is no substitute for alertness while in
the vicinity of an airport. It is essential that pilots be
alert and look for other traffic and exchange traffic
information when approaching or departing an
airport without an operating control tower. This is of
particular importance since other aircraft may not
have communication capability or, in some cases,
pilots may not communicate their presence or
intentions when operating into or out of such airports.
To achieve the greatest degree of safety, it is essential
that all radio-equipped aircraft transmit/receive on a
common frequency identified for the purpose of
airport advisories.
2. An airport may have a full or part-time tower
or FSS located on the airport, a full or part-time
UNICOM station or no aeronautical station at all.
There are three ways for pilots to communicate their
intention and obtain airport/traffic information when
operating at an airport that does not have an operating
tower: by communicating with an FSS, a UNICOM
operator, or by making a self-announce broadcast.
3. Many airports are now providing completely
automated weather, radio check capability and airport
advisory information on an automated UNICOM
system. These systems offer a variety of features,
typically selectable by microphone clicks, on the
UNICOM frequency. Availability of the automated
UNICOM will be published in the Airport/Facility
Directory and approach charts.
b. Communicating on a Common Frequency
1. The key to communicating at an airport
without an operating control tower is selection of the
correct common frequency. The acronym CTAF
which stands for Common Traffic Advisory
Frequency, is synonymous with this program. A
CTAF is a frequency designated for the purpose of
carrying out airport advisory practices while
operating to or from an airport without an operating
control tower. The CTAF may be a UNICOM,
MULTICOM, FSS, or tower frequency and is
identified in appropriate aeronautical publications.
AIM 2/14/08
4-1-3
Services Available to Pilots
TBL 4-1-1
Summary of Recommended Communication Procedures
Communication/Broadcast Procedures
Facility at Airport Frequency Use Outbound Inbound
Practice
Instrument
Approach
1. UNICOM (No Tower or
FSS)
Communicate with UNICOM
station on published CTAF
frequency (122.7; 122.8; 122.725;
122.975; or 123.0). If unable to
contact UNICOM station, use
self-announce procedures on
CTAF.
Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
2. No Tower, FSS, or
UNICOM
Self-announce on MULTICOM
frequency 122.9.
Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
Departing final
approach fix
(name) or on final
approach segment
inbound.
3. No Tower in operation,
FSS open
Communicate with FSS on CTAF
frequency.
Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
Approach com-
pleted/terminated.
4. FSS Closed (No Tower) Self-announce on CTAF. Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
5. Tower or FSS not in
operation
Self-announce on CTAF. Before taxiing and
before taxiing on
the runway for
departure.
10 miles out.
Entering
downwind, base,
and final. Leaving
the runway.
2. The CTAF frequency for a particular airport
is contained in the A/FD, Alaska Supplement, Alaska
Terminal Publication, Instrument Approach Proce-
dure Charts, and Instrument Departure
Procedure_(DP) Charts. Also, the CTAF frequency
can be obtained by contacting any FSS. Use of the
appropriate CTAF, combined with a visual alertness
and application of the following recommended good
operating practices, will enhance safety of flight into
and out of all uncontrolled airports.
c. Recommended Traffic Advisory Practices
1. Pilots of inbound traffic should monitor and
communicate as appropriate on the designated CTAF
from 10 miles to landing. Pilots of departing aircraft
should monitor/communicate on the appropriate
frequency from start-up, during taxi, and until
10_miles from the airport unless the CFRs or local
procedures require otherwise.
2. Pilots of aircraft conducting other than
arriving or departing operations at altitudes normally
used by arriving and departing aircraft should
monitor/communicate on the appropriate frequency
while within 10 miles of the airport unless required to
do otherwise by the CFRs or local procedures. Such
operations include parachute jumping/dropping, en
route, practicing maneuvers, etc.
REFERENCE-
AIM, Parachute Jump Aircraft Operations, Paragraph 3-5-4.
d. Airport Advisory/Information Services
Provided by a FSS
1. There are three advisory type services
provided at selected airports.
(a) Local Airport Advisory (LAA) is pro-
vided at airports that have a FSS physically located on
the airport, which does not have a control tower or
where the tower is operated on a part-time basis. The
CTAF for LAA airports is disseminated in the
appropriate aeronautical publications.
AIM 2/14/08
4-1-4 Services Available to Pilots
(b) Remote Airport Advisory (RAA) is
provided at selected very busy GA airports, which do
not have an operating control tower. The CTAF for
RAA airports is disseminated in the appropriate
aeronautical publications.
(c) Remote Airport Information Ser-
vice_(RAIS) is provided in support of special events
at nontowered airports by request from the airport
authority.
2. In communicating with a CTAF FSS, check
the airport's automated weather and establish
two-way communications before transmitting out-
bound/inbound intentions or information. An
inbound aircraft should initiate contact approximate-
ly 10 miles from the airport, reporting aircraft
identification and type, altitude, location relative to
the airport, intentions (landing or over flight),
possession of the automated weather, and request
airport advisory or airport information service. A
departing aircraft should initiate contact before
taxiing, reporting aircraft identification and type,
VFR or IFR, location on the airport, intentions,
direction of take-off, possession of the automated
weather, and request airport advisory or information
service. Also, report intentions before taxiing onto
the active runway for departure. If you must change
frequencies for other service after initial report to
FSS, return to FSS frequency for traffic update.
(a) Inbound
EXAMPLE-
Vero Beach radio, Centurion Six Niner Delta Delta is
ten_miles south, two thousand, landing Vero Beach. I have
the automated weather, request airport advisory.
(b) Outbound
EXAMPLE-
Vero Beach radio, Centurion Six Niner Delta Delta, ready
to taxi to runway 22, VFR, departing to the southwest. I
have the automated weather, request airport advisory.
3. Airport advisory service includes wind
direction and velocity, favored or designated runway,
altimeter setting, known airborne and ground traffic,
NOTAMs, airport taxi routes, airport traffic pattern
information, and instrument approach procedures.
These elements are varied so as to best serve the
current traffic situation. Some airport managers have
specified that under certain wind or other conditions
designated runways be used. Pilots should advise the
FSS of the runway they intend to use.
CAUTION-
All aircraft in the vicinity of an airport may not be in
communication with the FSS.
e. Information Provided by Aeronautical
Advisory Stations (UNICOM)
1. UNICOM is a nongovernment air/ground
radio communication station which may provide
airport information at public use airports where there
is no tower or FSS.
2. On pilot request, UNICOM stations may
provide pilots with weather information, wind
direction, the recommended runway, or other
necessary information. If the UNICOM frequency is
designated as the CTAF, it will be identified in
appropriate aeronautical publications.
f. Unavailability of Information from FSS or
UNICOM
Should LAA by an FSS or Aeronautical Advisory
Station UNICOM be unavailable, wind and weather
information may be obtainable from nearby
controlled airports via Automatic Terminal Informa-
tion Service (ATIS) or Automated Weather
Observing System (AWOS) frequency.
g. Self-Announce Position and/or Intentions
1. General. Self-announce is a procedure
whereby pilots broadcast their position or intended
flight activity or ground operation on the designated
CTAF. This procedure is used primarily at airports
which do not have an FSS on the airport. The
self-announce procedure should also be used if a pilot
is unable to communicate with the FSS on the
designated CTAF. Pilots stating, “Traffic in the area,
please advise” is not a recognized Self-Announce
Position and/or Intention phrase and should not be
used under any condition.
2. If an airport has a tower and it is temporarily
closed, or operated on a part-time basis and there is no
FSS on the airport or the FSS is closed, use the CTAF
to self-announce your position or intentions.
3. Where there is no tower, FSS, or UNICOM
station on the airport, use MULTICOM frequency
122.9 for self-announce procedures. Such airports
will be identified in appropriate aeronautical
information publications.
4. Practice Approaches. Pilots conducting
practice instrument approaches should be particular-
ly alert for other aircraft that may be departing in the
AIM 2/14/08
4-1-5
Services Available to Pilots
opposite direction. When conducting any practice
approach, regardless of its direction relative to other
airport operations, pilots should make announce-
ments on the CTAF as follows:
(a) Departing the final approach fix, inbound
(nonprecision approach) or departing the outer
marker or fix used in lieu of the outer marker, inbound
(precision approach);
(b) Established on the final approach segment
or immediately upon being released by ATC;
(c) Upon completion or termination of the
approach; and
(d) Upon executing the missed approach
procedure.
5. Departing aircraft should always be alert for
arrival aircraft coming from the opposite direction.
6. Recommended self-announce phraseologies:
It should be noted that aircraft operating to or from
another nearby airport may be making self-announce
broadcasts on the same UNICOM or MULTICOM
frequency. To help identify one airport from another,
the airport name should be spoken at the beginning
and end of each self-announce transmission.
(a) Inbound
EXAMPLE-
Strawn traffic, Apache Two Two Five Zulu, (position),
(altitude), (descending) or entering downwind/base/final
(as appropriate) runway one seven full stop, touch-andgo, Strawn.
Strawn traffic Apache Two Two Five Zulu clear of runway
one seven Strawn.
(b) Outbound
EXAMPLE-
Strawn traffic, Queen Air Seven One Five Five Bravo
(location on airport) taxiing to runway two six Strawn.
Strawn traffic, Queen Air Seven One Five Five Bravo
departing runway two six. Departing the pattern to the
(direction), climbing to (altitude) Strawn.
(c) Practice Instrument Approach
EXAMPLE-
Strawn traffic, Cessna Two One Four Three Quebec
(position from airport) inbound descending through
(altitude) practice (name of approach) approach runway
three five Strawn.
Strawn traffic, Cessna Two One Four Three Quebec
practice (type) approach completed or terminated runway
three five Strawn.
h. UNICOM Communications Procedures
1. In communicating with a UNICOM station,
the following practices will help reduce frequency
congestion, facilitate a better understanding of pilot
intentions, help identify the location of aircraft in the
traffic pattern, and enhance safety of flight:
(a) Select the correct UNICOM frequency.
(b) State the identification of the UNICOM
station you are calling in each transmission.
(c) Speak slowly and distinctly.
(d) Report approximately 10 miles from the
airport, reporting altitude, and state your aircraft type,
aircraft identification, location relative to the airport,
state whether landing or overflight, and request wind
information and runway in use.
(e) Report on downwind, base, and final
approach.
(f) Report leaving the runway.
2. Recommended UNICOM phraseologies:
(a) Inbound
PHRASEOLOGY-
FREDERICK UNICOM CESSNA EIGHT ZERO ONE
TANGO FOXTROT 10 MILES SOUTHEAST
DESCENDING THROUGH (altitude) LANDING
FREDERICK, REQUEST WIND AND RUNWAY
INFORMATION FREDERICK.
FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE
TANGO FOXTROT ENTERING DOWNWIND/BASE/
FINAL (as appropriate) FOR RUNWAY ONE NINER (full
stop/touch-and-go) FREDERICK.
FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE
TANGO FOXTROT CLEAR OF RUNWAY ONE NINER
FREDERICK.
(b) Outbound
PHRASEOLOGY-
FREDERICK UNICOM CESSNA EIGHT ZERO ONE
TANGO FOXTROT (location on airport) TAXIING TO
RUNWAY ONE NINER, REQUEST WIND AND TRAFFIC
INFORMATION FREDERICK.
FREDERICK TRAFFIC CESSNA EIGHT ZERO ONE
TANGO FOXTROT DEPARTING RUNWAY ONE NINER.
“REMAINING IN THE PATTERN” OR “DEPARTING
THE PATTERN TO THE (direction) (as appropriate)”
FREDERICK.
AIM 2/14/08
4-1-6 Services Available to Pilots
4-1-10. IFR Approaches/Ground Vehicle
Operations
a. IFR Approaches. When operating in accor-
dance with an IFR clearance and ATC approves a
change to the advisory frequency, make an
expeditious change to the CTAF and employ the
recommended traffic advisory procedures.
b. Ground Vehicle Operation. Airport ground
vehicles equipped with radios should monitor the
CTAF frequency when operating on the airport
movement area and remain clear of runways/taxi-
ways being used by aircraft. Radio transmissions
from ground vehicles should be confined to
safety-related matters.
c. Radio Control of Airport Lighting Systems.
Whenever possible, the CTAF will be used to control
airport lighting systems at airports without operating
control towers. This eliminates the need for pilots to
change frequencies to turn the lights on and allows a
continuous listening watch on a single frequency. The
CTAF is published on the instrument approach chart
and in other appropriate aeronautical information
publications. For further details concerning radio
controlled lights, see AC 150/5340-27, Air-to-
Ground Radio Control of Airport Lighting Systems.
4-1-11. Designated UNICOM/MULTICOM
Frequencies
Frequency use
a. The following listing depicts UNICOM and
MULTICOM frequency uses as designated by the
Federal Communications Commission (FCC).
(See TBL 4-1-2.)
TBL 4-1-2
Unicom/Multicom Frequency Usage
Use Frequency
Airports without an operating
control tower.
122.700
122.725
122.800
122.975
123.000
123.050
123.075
(MULTICOM FREQUENCY)
Activities of a temporary, seasonal,
emergency nature or search and
rescue, as well as, airports with no
tower, FSS, or UNICOM.
122.900
(MULTICOM FREQUENCY)
Forestry management and fire
suppression, fish and game
management and protection, and
environmental monitoring and
protection.
122.925
Airports with a control tower or
FSS on airport.
122.950
NOTE1. In some areas of the country, frequency interference
may be encountered from nearby airports using the same
UNICOM frequency. Where there is a problem, UNICOM
operators are encouraged to develop a “least interfer-
ence” frequency assignment plan for airports concerned
using the frequencies designated for airports without
operating control towers. UNICOM licensees are
encouraged to apply for UNICOM 25 kHz spaced channel
frequencies. Due to the extremely limited number of
frequencies with 50 kHz channel spacing, 25 kHz channel
spacing should be implemented. UNICOM licensees may
then request FCC to assign frequencies in accordance with
the plan, which FCC will review and consider for approval.
2. Wind direction and runway information may not be
available on UNICOM frequency 122.950.
b. The following listing depicts other frequency
uses as designated by the Federal Communications
Commission (FCC). (See TBL 4-1-3.)
AIM 2/14/08
4-1-7
Services Available to Pilots
TBL 4-1-3
Other Frequency Usage Designated by FCC
Use Frequency
Air-to-air communication
(private fixed wing aircraft).
122.750
Air-to-air communications
(general aviation helicopters).
123.025
Aviation instruction, Glider, Hot Air
Balloon (not to be used for
advisory service).
123.300
123.500
4-1-12. Use of UNICOM for ATC Purposes
UNICOM service may be used for ATC purposes,
only under the following circumstances:
a. Revision to proposed departure time.
b. Takeoff, arrival, or flight plan cancellation
time.
c. ATC clearance, provided arrangements are
made between the ATC facility and the UNICOM
licensee to handle such messages.
4-1-13. Automatic Terminal Information
Service (ATIS)
a. ATIS is the continuous broadcast of recorded
noncontrol information in selected high activity
terminal areas. Its purpose is to improve controller
effectiveness and to relieve frequency congestion by
automating the repetitive transmission of essential
but routine information. The information is continuously broadcast over a discrete VHF radio frequency
or the voice portion of a local NAVAID. ATIS
transmissions on a discrete VHF radio frequency are
engineered to be receivable to a maximum of 60 NM
from the ATIS site and a maximum altitude of
25,000 feet AGL. At most locations, ATIS signals
may be received on the surface of the airport, but local
conditions may limit the maximum ATIS reception
distance and/or altitude. Pilots are urged to cooperate
in the ATIS program as it relieves frequency
congestion on approach control, ground control, and
local control frequencies. The A/FD indicates
airports for which ATIS is provided.
b. ATIS information includes the time of the latest
weather sequence, ceiling, visibility, obstructions to
visibility, temperature, dew point (if available), wind
direction (magnetic), and velocity, altimeter, other
pertinent remarks, instrument approach and runway
in use. The ceiling/sky condition, visibility, and
obstructions to vision may be omitted from the ATIS
broadcast if the ceiling is above 5,000 feet and the
visibility is more than 5 miles. The departure runway
will only be given if different from the landing
runway except at locations having a separate ATIS for
departure. The broadcast may include the appropriate
frequency and instructions for VFR arrivals to make
initial contact with approach control. Pilots of aircraft
arriving or departing the terminal area can receive the
continuous ATIS broadcast at times when cockpit
duties are least pressing and listen to as many repeats
as desired. ATIS broadcast shall be updated upon the
receipt of any official hourly and special weather. A
new recording will also be made when there is a
change in other pertinent data such as runway change,
instrument approach in use, etc.
EXAMPLE-
Dulles International information Sierra. 1300 zulu
weather. Measured ceiling three thousand overcast.
Visibility three, smoke. Temperature six eight. Wind
three five zero at eight. Altimeter two niner niner two. ILS
runway one right approach in use. Landing runway one
right and left. Departure runway three zero. Armel
VORTAC out of service. Advise you have Sierra.
c. Pilots should listen to ATIS broadcasts
whenever ATIS is in operation.
d. Pilots should notify controllers on initial
contact that they have received the ATIS broadcast by
repeating the alphabetical code word appended to the
broadcast.
EXAMPLE-
“Information Sierra received.”
e. When a pilot acknowledges receipt of the ATIS
broadcast, controllers may omit those items contained in the broadcast if they are current. Rapidly
changing conditions will be issued by ATC and the
ATIS will contain words as follows:
EXAMPLE-
“Latest ceiling/visibility/altimeter/wind/(other conditions) will be issued by approach control/tower.”
NOTE-
The absence of a sky condition or ceiling and/or visibility
on ATIS indicates a sky condition or ceiling of 5,000 feet or
above and visibility of 5 miles or more. A remark may be
made on the broadcast, “the weather is better than
5000 and 5,” or the existing weather may be broadcast.
f. Controllers will issue pertinent information to
pilots who do not acknowledge receipt of a broadcast
AIM 2/14/4-1-8 Services Available to Pilots
or who acknowledge receipt of a broadcast which is
not current.
g. To serve frequency limited aircraft, FSSs are
equipped to transmit on the omnirange frequency at
most en route VORs used as ATIS voice outlets. Such
communication interrupts the ATIS broadcast. Pilots
of aircraft equipped to receive on other FSS
frequencies are encouraged to do so in order that these
override transmissions may be kept to an absolute
minimum.
h. While it is a good operating practice for pilots
to make use of the ATIS broadcast where it is
available, some pilots use the phrase “have numbers”
in communications with the control tower. Use of this
phrase means that the pilot has received wind,
runway, and altimeter information ONLY and the
tower does not have to repeat this information. It does
not indicate receipt of the ATIS broadcast and should
never be used for this purpose.
4-1-14. Automatic Flight Information
Service (AFIS) -Alaska FSSs Only
a. Alaska FSSs AFIS is the continuous broadcast
of recorded noncontrol information at airports in
Alaska where a Flight Service Station (FSS) provides
local airport advisory service. Its purpose is to
improve FSS Specialist efficiency by reducing
frequency congestion on the local airport advisory
frequency. The AFIS broadcast will automate the
repetitive transmission of essential but routine
information (weather, favored runway, breaking
action, airport NOTAMs, other applicable information). The information is continuously broadcast over
a discrete VHF radio frequency (usually the ASOS
frequency). Use of AFIS is not mandatory, but pilots
who choose to utilize two-way radio communications with the FSS are urged to listen to AFIS, as it
relieves frequency congestion on the local airport
advisory frequency. AFIS broadcasts are updated
upon the receipt of any official hourly and special
weather, worsening braking action reports, and
changes in other pertinent data. When a pilot
acknowledges receipt of the AFIS broadcast, FSS
Specialists may omit those items contained in the
broadcast if they are current. When rapidly changing
conditions exist, the latest ceiling, visibility,
altimeter, wind or other conditions may be omitted
from the AFIS and will be issued by the Flight Service
Specialist on the appropriate radio frequency.
EXAMPLE-
“Kotzebue information ALPHA. One six five five zulu.
Wind, two one zero at five; visibility two, fog; ceiling one
hundred overcast; temperature minus one two, dew point
minus one four; altimeter three one zero five. Altimeter in
excess of three one zero zero, high pressure altimeter
setting procedures are in effect. Favored runway two six.
Weather in Kotzebue surface area is below V-F-R
minima -an ATC clearance is required. Contact
Kotzebue Radio on 123.6 for traffic advisories and advise
intentions. Notice to Airmen, Hotham NDB out of service.
Transcribed Weather Broadcast out of service. Advise on
initial contact you have ALPHA.”
NOTE-
The absence of a sky condition or ceiling and/or visibility
on Alaska FSS AFIS indicates a sky condition or ceiling of
5,000 feet or above and visibility of 5 miles or more. A
remark may be made on the broadcast, “the weather is
better than 5000 and 5.”
b. Pilots should listen to Alaska FSSs AFIS
broadcasts whenever Alaska FSSs AFIS is in
operation.
NOTE-
Some Alaska FSSs are open part time and/or seasonally.
c. Pilots should notify controllers on initial
contact that they have received the Alaska FSSs
AFIS broadcast by repeating the phonetic alphabetic
letter appended to the broadcast.
EXAMPLE-
“Information Alpha received.”
d. While it is a good operating practice for pilots
to make use of the Alaska FSS AFIS broadcast where
it is available, some pilots use the phrase “have
numbers” in communications with the FSS. Use of
this phrase means that the pilot has received wind,
runway, and altimeter information ONLY and the
Alaska FSS does not have to repeat this information.
It does not indicate receipt of the AFIS broadcast and
should never be used for this purpose.
4-1-15. Radar Traffic Information Service
This is a service provided by radar ATC facilities.
Pilots receiving this service are advised of any radar
target observed on the radar display which may be in
such proximity to the position of their aircraft or its
intended route of flight that it warrants their attention.
This service is not intended to relieve the pilot of the
responsibility for continual vigilance to see and avoid
other aircraft.
3/15/07 7110.65R CHG 2 AIM 7/31/08
AIM 2/14/08
4-1-9
Services Available to Pilots
a. Purpose of the Service
1. The issuance of traffic information as
observed on a radar display is based on the principle
of assisting and advising a pilot that a particular radar
target’s position and track indicates it may intersect or
pass in such proximity to that pilot’s intended flight
path that it warrants attention. This is to alert the pilot
to the traffic, to be on the lookout for it, and thereby
be in a better position to take appropriate action
should the need arise.
2. Pilots are reminded that the surveillance radar
used by ATC does not provide altitude information
unless the aircraft is equipped with Mode C and the
radar facility is capable of displaying altitude
information.
b. Provisions of the Service
1. Many factors, such as limitations of the radar,
volume of traffic, controller workload and communications frequency congestion, could prevent the
controller from providing this service. Controllers
possess complete discretion for determining whether
they are able to provide or continue to provide this
service in a specific case. The controller’s reason
against providing or continuing to provide the service
in a particular case is not subject to question nor need
it be communicated to the pilot. In other words, the
provision of this service is entirely dependent upon
whether controllers believe they are in a position to
provide it. Traffic information is routinely provided
to all aircraft operating on IFR flight plans except
when the pilot declines the service, or the pilot is
operating within Class A airspace. Traffic information may be provided to flights not operating on IFR
flight plans when requested by pilots of such flights.
NOTE-
Radar ATC facilities normally display and monitor both
primary and secondary radar when it is available, except
that secondary radar may be used as the sole display
source in Class A airspace, and under some circumstances
outside of Class A airspace (beyond primary coverage and
in en route areas where only secondary is available).
Secondary radar may also be used outside Class A
airspace as the sole display source when the primary radar
is temporarily unusable or out of service. Pilots in contact
with the affected ATC facility are normally advised when
a temporary outage occurs; i.e., “primary radar out of
service; traffic advisories available on transponder
aircraft only.” This means simply that only the aircraft
which have transponders installed and in use will be
depicted on ATC radar indicators when the primary radar
is temporarily out of service.
