Communication Equipment
Navigation/Communication Equipment
Civilian pilots communicate with ATC on frequencies in
the very high frequency (VHF) range between 118.000 and
136.975 MHz. To derive full benefit from the ATC system,
radios capable of 25 kHz spacing are required (e.g., 134.500,
134.575, 134.600). If ATC assigns a frequency that cannot
be selected, ask for an alternative frequency.
Figure illustrates a typical radio panel installation
consisting of a communications transceiver on the left and
a navigational receiver on the right. Many radios allow the
pilot to have one or more frequencies stored in memory and
one frequency active for transmitting and receiving (calledsimplex operation). It is possible to communicate with some
flight service stations (FSS) by transmitting on 122.1 MHz
(selected on the communication radio) and receiving on a
VHF omnidirectional range (VOR) frequency (selected on
the navigation radio). This is called duplex operation.
An audio panel allows a pilot to adjust the volume of the
selected receiver(s) and to select the desired transmitter. The audio panel has two positions for receiver
selection, cabin speaker, and headphone (some units might
have a center “OFF” position). Use of a hand-held microphone
and the cabin speaker introduces the distraction of reaching
for and hanging up the microphone. A headset with a boom
microphone is recommended for clear communications. The
microphone should be positioned close to the lips to reduce the possibility of ambient flight deck noise interfering with
transmissions to the controller. Headphones deliver the
received signal directly to the ears; therefore, ambient noise
does not interfere with the pilot’s ability to understand the
transmission.
Switching the transmitter selector between COM1 and
COM2 changes both transmitter and receiver frequencies.
It is necessary only when a pilot wants to monitor one
frequency while transmitting on another. One example is
listening to Automatic Terminal Information Service (ATIS)
on one receiver while communicating with ATC on the
other. Monitoring a navigation receiver to check for proper
identification is another reason to use the switch panel.
Most audio switch panels also include a marker beacon
receiver. All marker beacons transmit on 75 MHz, so there
is no frequency selector.
Figure illustrates an increasingly popular form of
navigation/communication radio; it contains a global
positioning system (GPS) receiver and a communications
transceiver. Using its navigational capability, this unit can
determine when a flight crosses an airspace boundary or fix
and can automatically select the appropriate communications
frequency for that location in the communications radio.
Radar and Transponders
ATC radars have a limited ability to display primary returns,
which is energy reflected from an aircraft’s metallic structure.
Their ability to display secondary returns (transponder replies
to ground interrogation signals) makes possible the many
advantages of automation.
A transponder is a radar beacon transmitter/receiver installed
in the instrument panel. ATC beacon transmitters send out
interrogation signals continuously as the radar antenna
rotates. When an interrogation is received by a transponder, a
coded reply is sent to the ground station where it is displayed
on the controller’s scope. A reply light on the transponder
panel flickers every time it receives and replies to a radar
interrogation. Transponder codes are assigned by ATC.
When a controller asks a pilot to “ident” and the ident button
is pushed, the return on the controller’s scope is intensified for
precise identification of a flight. When requested, briefly push
the ident button to activate this feature. It is good practice
for pilots to verbally confirm that they have changed codes
or pushed the ident button.
Mode C (Altitude Reporting)
Primary radar returns indicate only range and bearing from
the radar antenna to the target; secondary radar returns can
display altitude, Mode C, on the control scope if the aircraft
is equipped with an encoding altimeter or blind encoder. In
either case, when the transponder’s function switch is in the
ALT position, the aircraft’s pressure altitude is sent to the
controller. Adjusting the altimeter’s Kollsman window has
no effect on the altitude read by the controller.
Transponders, when installed, must be ON at all times when
operating in controlled airspace; altitude reporting is required
by regulation in Class B and Class C airspace and inside a
30-mile circle surrounding the primary airport in Class B
airspace. Altitude reporting should also be ON at all times.
Communication Procedures
Clarity in communication is essential for a safe instrument
flight. This requires pilots and controllers to use terms that
are understood by both—the Pilot/Controller Glossary in the
Aeronautical Information Manual (AIM) is the best source of
terms and definitions. The AIM is revised twice a year and
new definitions are added, so the glossary should be reviewed
frequently. Because clearances and instructions are comprised
largely of letters and numbers, a phonetic pronunciation guide
has been developed for both.
ATC must follow the guidance of the Air Traffic Control
Manual when communicating with pilots. The manual
presents the controller with different situations and prescribes
precise terminology that must be used. This is advantageous
for pilots because once they have recognized a pattern or
format, they can expect future controller transmissions
to follow that format. Controllers are faced with a wide
variety of communication styles based on pilot experience,
proficiency, and professionalism.
Pilots should study the examples in the AIM, listen to
other pilots communicate, and apply the lessons learned
to their own communications with ATC. Pilots should ask
for clarification of a clearance or instruction. If necessary,
use plain English to ensure understanding, and expect the
controller to reply in the same way. A safe instrument flight
is the result of cooperation between controller and pilot.
Communication Facilities
The controller’s primary responsibility is separation of
aircraft operating under IFR. This is accomplished with ATC
facilities, to include the FSS, airport traffic control tower
(ATCT), terminal radar approach control (TRACON), and
air route traffic control center (ARTCC).
Flight Service Stations (FSS)
A pilot’s first contact with ATC is usually through FSS,
either by radio or telephone. FSSs provide pilot briefings,
receive and process flight plans, relay ATC clearances,
originate Notices to Airmen (NOTAMs), and broadcast
aviation weather. Some facilities provide En Route Flight
Advisory Service (EFAS), take weather observations,
and advise United States Customs and Immigration of
international flights.
Telephone contact with Flight Service can be obtained
by dialing 1-800-WX-BRIEF. This number can be used
anywhere in the United States and connects to the nearest
FSS based on the area code from which the call originates.
There are a variety of methods of making radio contact:
direct transmission, remote communication outlets (RCOs), ground communication outlets (GCOs), and by using duplex
transmissions through navigational aids (NAVAIDs). The
best source of information on frequency usage is the Airport/
Facility Directory (A/FD) and the legend panel on sectional
charts also contains contact information.
The briefer sends a flight plan to the host computer at the
ARTCC (Center). After processing the flight plan, the
computer sends flight strips to the tower, to the radar facility
that handles the departure route, and to the Center controller
whose sector the flight first enters. Figure shows a typical
strip. These strips are delivered approximately 30 minutes
prior to the proposed departure time. Strips are delivered to
en route facilities 30 minutes before the flight is expected to
enter their airspace. If a flight plan is not opened, it will “time
out” 2 hours after the proposed departure time.
When departing an airport in Class G airspace, a pilot receives
an IFR clearance from the FSS by radio or telephone. It
contains either a clearance void time, in which case an aircraft
must be airborne prior to that time, or a release time. Pilots
should not take off prior to the release time. Pilots can help
the controller by stating how soon they expect to be airborne.
If the void time is, for example, 10 minutes past the hour and
an aircraft is airborne at exactly 10 minutes past the hour,
the clearance is void—a pilot must take off prior to the void
time. A specific void time may be requested when filing a
flight plan.
ATC Towers
Several controllers in the tower cab are involved in handling
an instrument flight. Where there is a dedicated clearance
delivery position, that frequency is found in the A/FD and
on the instrument approach chart for the departure airport.
Where there is no clearance delivery position, the ground
controller performs this function. At the busiest airports, pretaxi clearance is required; the frequency for pre-taxi clearance
can be found in the A/FD. Taxi clearance should be requested
not more than 10 minutes before proposed taxi time.
It is recommended that pilots read their IFR clearance back to
the clearance delivery controller. Instrument clearances can
be overwhelming when attempting to copy them verbatim,
but they follow a format that allows a pilot to be prepared
when responding “Ready to copy.” The format is: clearance
limit (usually the destination airport); route, including any
departure procedure; initial altitude; frequency (for departure control); and transponder code. With the exception of the
transponder code, a pilot knows most of these items before
engine start. One technique for clearance copying is writing
C-R-A-F-T.
Assume an IFR flight plan has been filed from Seattle,
Washington to Sacramento, California via V-23 at 7,000
feet. Traffic is taking off to the north from Seattle-Tacoma
(Sea-Tac) airport and, by monitoring the clearance delivery
frequency, a pilot can determine the departure procedure
being assigned to southbound flights. The clearance limit
is the destination airport, so write “SAC” after the letter C.
Write “SEATTLE TWO – V23” after R for Route because
departure control issued this departure to other flights. Write
“70” after the A, the departure control frequency printed on
the approach charts for Sea-Tac after F, and leave the space
after the letter T blank—the transponder code is generated by
computer and can seldom be determined in advance. Then,
call clearance delivery and report “Ready to copy.”
As the controller reads the clearance, check it against what
is already written down; if there is a change, draw a line
through that item and write in the changed item. Chances
are the changes are minimal, and most of the clearance is
copied before keying the microphone. Still, it is worthwhile
to develop clearance shorthand to decrease the verbiage that
must be copied (see Appendix 1).
Pilots are required to have either the text of a departure
procedure (DP) or a graphic representation (if one is
available), and should review it before accepting a clearance.
This is another reason to find out ahead of time which DP is
in use. If the DP includes an altitude or a departure control
frequency, those items are not included in the clearance.
The last clearance received supersedes all previous clearances.
For example, if the DP says “Climb and maintain 2,000 feet,
expect higher in 6 miles,” but upon contacting the departure
controller a new clearance is received: “Climb and maintain
8,000 feet,” the 2,000 feet restriction has been canceled. This
rule applies in both terminal and Center airspace.
When reporting “ready to copy” an IFR clearance before
the strip has been received from the Center computer, pilots
are advised “clearance on request.” The controller initiates
contact when it has been received. This time can be used for
taxi and pre-takeoff checks.
The local controller is responsible for operations in the Class
D airspace and on the active runways. At some towers,
designated as IFR towers, the local controller has vectoring
authority. At visual flight rules (VFR) towers, the local
controller accepts inbound IFR flights from the terminal radar
facility and cannot provide vectors. The local controller also
coordinates flights in the local area with radar controllers.
Although Class D airspace normally extends 2,500 feet above
field elevation, towers frequently release the top 500 feet to
the radar controllers to facilitate overflights. Accordingly,
when a flight is vectored over an airport at an altitude that
appears to enter the tower controller’s airspace, there is no
need to contact the tower controller—all coordination is
handled by ATC.
The departure radar controller may be in the same building
as the control tower, but it is more likely that the departure
radar position is remotely located. The tower controller will
not issue a takeoff clearance until the departure controller
issues a release.
Terminal Radar Approach Control (TRACON)
TRACONs are considered terminal facilities because they
provide the link between the departure airport and the en route
structure of the NAS. Terminal airspace normally extends 30
nautical miles (NM) from the facility with a vertical extent of
10,000 feet; however, dimensions vary widely. Class B and
Class C airspace dimensions are provided on aeronautical
charts. At terminal radar facilities, the airspace is divided
into sectors, each with one or more controllers, and each
sector is assigned a discrete radio frequency. All terminal
facilities are approach controls and should be addressed
as “Approach” except when directed to do otherwise (e.g.,
“Contact departure on 120.4.”).
Terminal radar antennas are located on or adjacent to the
airport. Figure shows a typical configuration. Terminal
controllers can assign altitudes lower than published
procedural altitudes called minimum vectoring altitudes
(MVAs). These altitudes are not published or accessible
to pilots, but are displayed at the controller’s position. However, when pilots are assigned an altitude
that seems to be too low, they should query the controller
before descending.
When a pilot accepts a clearance and reports ready for takeoff,
a controller in the tower contacts the TRACON for a release.
An aircraft is not cleared for takeoff until the departure
controller can fit the flight into the departure flow. A pilot may
have to hold for release. When takeoff clearance is received,
the departure controller is aware of the flight and is waiting
for a call. All of the information the controller needs is on
the departure strip or the computer screen; there is no need to
repeat any portion of the clearance to that controller. Simply
establish contact with the facility when instructed to do so
by the tower controller. The terminal facility computer picks up the transponder and initiates tracking as soon as it detects
the assigned code. For this reason, the transponder should
remain on standby until takeoff clearance has been received.
The aircraft appears on the controller’s radar display as a
target with an associated data block that moves as the aircraft
moves through the airspace. The data block includes aircraft
identification, aircraft type, altitude, and airspeed.
A TRACON controller uses Airport Surveillance Radar
(ASR) to detect primary targets and Automated Radar
Terminal Systems (ARTS) to receive transponder signals;
the two are combined on the controller’s scope.
At facilities with ASR-3 equipment, radar returns from
precipitation are not displayed as varying levels of intensity,
and controllers must rely on pilot reports and experience
to provide weather avoidance information. With ASR-9
equipment, the controller can select up to six levels of
intensity. Light precipitation does not require avoidance
tactics but precipitation levels of moderate, heavy, or
extreme should cause pilots to plan accordingly. Along
with precipitation, the pilot must additionally consider the
temperature, which if between –20° and +5 °C causes icing
even during light precipitation. The returns from higher levels
of intensity may obscure aircraft data blocks, and controllers
may select the higher levels only on pilot request. When
uncertainty exists about the weather ahead, ask the controller
if the facility can display intensity levels—pilots of small
aircraft should avoid intensity levels 3 or higher.
Tower En Route Control (TEC)
At many locations, instrument flights can be conducted
entirely in terminal airspace. These tower en route control
(TEC) routes are generally for aircraft operating below
10,000 feet, and they can be found in the A/FD. Pilots desiring
to use TEC should include that designation in the remarks
section of the flight plan.
Pilots are not limited to the major airports at the city pairs
listed in the A/FD. For example, a tower en route flight from
an airport in New York (NYC) airspace could terminate
at any airport within approximately 30 miles of Bradley
International (BDL) airspace, such as Hartford (HFD).
Air Route Traffic Control Center (ARTCC)
ARTCC facilities are responsible for maintaining separation
between IFR flights in the en route structure. Center radars
(Air Route Surveillance Radar (ARSR)) acquire and track
transponder returns using the same basic technology as
terminal radars.
Earlier Center radars display weather as an area of slashes
(light precipitation) and Hs (moderate rainfall), as illustrated
in Figure. Because the controller cannot detect higher
levels of precipitation, pilots should be wary of areas
showing moderate rainfall. Newer radar displays show
weather as three levels of blue. Controllers can select the
level of weather to be displayed. Weather displays of higher
levels of intensity can make it difficult for controllers to
see aircraft data blocks, so pilots should not expect ATC
to keep weather displayed continuously.
Center airspace is divided into sectors in the same manner
as terminal airspace; additionally, most Center airspace is
divided by altitudes into high and low sectors. Each sector
has a dedicated team of controllers and a selection of radio
frequencies because each Center has a network of remote
transmitter/receiver sites. All Center frequencies can be found
in the back of the A/FD in the format shown in Figure;
they are also found on en route charts.
Each ARTCC’s area of responsibility covers several states;
when flying from the vicinity of one remote communication
site toward another, expect to hear the same controller on
different frequencies.
Center Approach/Departure Control
The majority of airports with instrument approaches do not
lie within terminal radar airspace and, when operating to or
from these airports, pilots communicate directly with the
Center controller. Departing from a tower-controlled airport,
the tower controller provides instructions for contacting the
appropriate Center controller. When departing an airport
without an operating control tower, the clearance includes
instructions such as “Upon entering controlled airspace,
contact Houston Center on 126.5.” Pilots are responsible
for terrain clearance until reaching the controller’s MVA.
Simply hearing “Radar contact” does not relieve a pilot of
this responsibility.
If obstacles in the departure path require a steeperthan-standard climb gradient (200 feet per nautical mile
(FPNM)), then the controller advises the pilot. However,
it is the pilot’s responsibility to check the departure airport
listing in the A/FD to determine if there are trees or wires
in the departure path. When in doubt, ask the controller for
the required climb gradient.
A common clearance in these situations is “When able,
proceed direct to the Astoria VOR…” The words “when able”
mean to proceed to the waypoint, intersection, or NAVAID
when the pilot is able to navigate directly to that point using
onboard available systems providing proper guidance, usable
signal, etc. If provided such guidance while flying VFR, the
pilot remains responsible for terrain and obstacle clearance.
Using the standard climb gradient, an aircraft is 2 miles
from the departure end of the runway before it is safe to
turn (400 feet above ground level (AGL)). When a Center
controller issues a heading, a direct route, or says “direct
when able,” the controller becomes responsible for terrain
and obstruction clearance.
Another common Center clearance is “Leaving (altitude)
fly (heading) or proceed direct when able.” This keeps the
terrain/obstruction clearance responsibility in the flight deck
until above the minimum IFR altitude. A controller cannot
issue an IFR clearance until an aircraft is above the minimum
IFR altitude unless it is able to climb in VFR conditions.
On a Center controller’s scope, 1 NM is about 1
⁄28 of an inch.
When a Center controller is providing Approach/Departure
control services at an airport many miles from the radar
antenna, estimating headings and distances is very difficult.
Controllers providing vectors to final must set the range on
their scopes to not more than 125 NM to provide the greatest
possible accuracy for intercept headings. Accordingly, at
locations more distant from a Center radar antenna, pilots
should expect a minimum of vectoring.
ATC Inflight Weather Avoidance
Assistance
ATC Radar Weather Displays
ATC radar systems are able to display areas of precipitation
by sending out a beam of radio energy that is reflected back to
the radar antenna when it strikes an object or moisture, which
may be in the form of rain drops, hail, or snow. The larger
the object, or the denser its reflective surface, the stronger
the return. Radar weather processors indicate the intensity
of reflective returns in terms of decibels with respect to the
radar reflectively factor (dBZ).
ATC systems cannot detect the presence or absence of
clouds. ATC radar systems can often determine the intensity
of a precipitation area, but the specific character of that area
(snow, rain, hail, VIRGA, etc.) cannot be determined. For
this reason, ATC refers to all weather areas displayed on
ATC radar scopes as “precipitation.”
All ATC facilities using radar weather processors with the
ability to determine precipitation intensity describes the
intensity to pilots as:
1. “LIGHT” (< 30 dBZ)
2. “MODERATE” (30 to 40 dBZ)
3. “HEAVY” (>40 to 50 dBZ)
4. “EXTREME” (>50 dBZ).
ARTCC controllers do not use the term “LIGHT” because
their systems do not display “LIGHT” precipitation
intensities. ATC facilities that, due to equipment limitations,
cannot display the intensity levels of precipitation, describe
the location of the precipitation area by geographic position or
position relative to the aircraft. Since the intensity level is not
available, the controller states, “INTENSITY UNKNOWN.”
ARTCC facilities normally use a Weather and Radar
Processor (WARP) to display a mosaic of data obtained from
multiple NEXRAD sites. The WARP processor is only used
in ARTCC facilities.
There is a time delay between actual conditions and those
displayed to the controller. For example, the precipitation
data on the ARTCC controller’s display could be up to 6
minutes old. When the WARP is not available, a secondary
system, the narrowband ARSR is utilized. The ARSR system
can display two distinct levels of precipitation intensity that
is described to pilots as “MODERATE” (30 to 40 dBZ) and
“HEAVY to EXTREME” (>40 dBZ).
ATC radar systems cannot detect turbulence. Generally,
turbulence can be expected to occur as the rate of rainfall or
intensity of precipitation increases. Turbulence associated
with greater rates of rainfall/precipitation is normally more
severe than any associated with lesser rates of rainfall/
precipitation. Turbulence should be expected to occur near
convective activity, even in clear air. Thunderstorms are a
form of convective activity that implies severe or greater
turbulence. Operation within 20 miles of thunderstorms
should be approached with great caution, as the severity of
turbulence can be markedly greater than the precipitation
intensity might indicate.
Weather Avoidance Assistance
ATC’s first duty priority is to separate aircraft and issue
safety alerts. ATC provides additional services to the extent
possible, contingent upon higher priority duties and other
factors including limitations of radar, volume of traffic,
frequency congestion, and workload. Subject to the above
factors/limitations, controllers issue pertinent information
on weather or chaff areas; and if requested, assist pilots, to
the extent possible, in avoiding areas of precipitation. Pilots
should respond to a weather advisory by acknowledging the
advisory and, if desired, requesting an alternate course of
action, such as:
1. Request to deviate off course by stating the direction
and number of degrees or miles needed to deviate from
the original course;
2. Request a change of altitude; or
3. Request routing assistance to avoid the affected
area. Because ATC radar systems cannot detect the
presence or absence of clouds and turbulence, such
assistance conveys no guarantee that the pilot will not
encounter hazards associated with convective activity.
Pilots wishing to circumnavigate precipitation areas
by a specific distance should make their desires
clearly known to ATC at the time of the request for
services. Pilots must advise ATC when they can
resume normal navigation.
IFR pilots shall not deviate from their assigned course or
altitude without an ATC clearance. Plan ahead for possible
course deviations because hazardous convective conditions
can develop quite rapidly. This is important to consider
because the precipitation data displayed on ARTCC radar
scopes can be up to 6 minutes old, and thunderstorms can
develop at rates exceeding 6,000 feet per minute (fpm). When
encountering weather conditions that threaten the safety of
the aircraft, the pilot may exercise emergency authority as stated in 14 CFR part 91, section 91.3 should an immediate
deviation from the assigned clearance be necessary and time
does not permit approval by ATC.
Generally, when weather disrupts the flow of air traffic,
greater workload demands are placed on the controller.
Requests for deviations from course and other services
should be made as far in advance as possible to better
assure the controller’s ability to approve these requests
promptly. When requesting approval to detour around
weather activity, include the following information to
facilitate the request:
1. The proposed point where detour commences;
2. The proposed route and extent of detour (direction
and distance);
3. The point where original route will be resumed;
4. Flight conditions (instrument meteorological
conditions (IMC) or visual meteorological conditions
(VMC);
5. Whether the aircraft is equipped with functioning
airborne radar; and
6. Any further deviation that may become necessary.
To a large degree, the assistance that might be rendered
by ATC depends upon the weather information available
to controllers. Due to the extremely transitory nature of
hazardous weather, the controller’s displayed precipitation
information may be of limited value.
Obtaining IFR clearance or approval to circumnavigate
hazardous weather can often be accommodated more readily
in the en route areas away from terminals because there
is usually less congestion and, therefore, greater freedom
of action. In terminal areas, the problem is more acute
because of traffic density, ATC coordination requirements,
complex departure and arrival routes, and adjacent airports.
As a consequence, controllers are less likely to be able to
accommodate all requests for weather detours in a terminal
area. Nevertheless, pilots should not hesitate to advise
controllers of any observed hazardous weather and should
specifically advise controllers if they desire circumnavigation
of observed weather.
Pilot reports (PIREPs) of flight conditions help define the
nature and extent of weather conditions in a particular area.
These reports are disseminated by radio and electronic means
to other pilots. Provide PIREP information to ATC regarding
pertinent flight conditions, such as:
1. Turbulence;
2. Visibility; 3. Cloud tops and bases; and
4. The presence of hazards such as ice, hail, and lightning
Approach Control Facility
An approach control facility is a terminal ATC facility
that provides approach control service in the terminal area.
Services are provided for arriving and departing VFR and
IFR aircraft and, on occasion, en route aircraft. In addition,
for airports with parallel runways with ILS or LDA
approaches, the approach control facility provides monitoring
of the approaches.
Approach Control Advances
Precision Runway Monitor (PRM)
Over the past few years, a new technology has been installed
at airports that permits a decreased separation distance
between parallel runways. The system is called a Precision
Runway Monitor (PRM) and is comprised of high-update
radar, high-resolution ATC displays, and PRM-certified
controllers.
PRM Radar
The PRM uses a Monopulse Secondary Surveillance Radar
(MSSR) that employs electronically-scanned antennas.
Because the PRM has no scan rate restrictions, it is capable
of providing a faster update rate (up to 1.0 second) over
conventional systems, thereby providing better target
presentation in terms of accuracy, resolution, and track
prediction. The system is designed to search, track, process,
and display SSR-equipped aircraft within airspace of over
30 miles in range and over 15,000 feet in elevation. Visual
and audible alerts are generated to warn controllers to take
corrective actions.
PRM Benefits
Typically, PRM is used with dual approaches with
centerlines separated less than 4,300 feet but not less
than 3,000 feet (under most conditions). Separating the two final approach courses is a No
Transgression Zone (NTZ) with surveillance of that zone
provided by two controllers, one for each active approach.
The system tracking software provides PRM monitor
controllers with aircraft identification, position, speed,
projected position, as well as visual and aural alerts.
Control Sequence
The IFR system is flexible and accommodating if pilots
do their homework, have as many frequencies as possible
written down before they are needed, and have an alternate
in mind if the flight cannot be completed as planned.
Pilots should familiarize themselves with all the facilities and services available along the planned route of flight. Always know where the nearest VFR
conditions can be found, and be prepared to head in that
direction if the situation deteriorates.
A typical IFR flight, with departure and arrival at airports with
control towers, would use the ATC facilities and services in
the following sequence:
1. FSS: Obtain a weather briefing for a departure,
destination and alternate airports, and en route
conditions, and then file a flight plan by calling
1-800-WX-BRIEF.
2. ATIS: Preflight complete, listen for present conditions
and the approach in use.
3. Clearance Delivery: Prior to taxiing, obtain a
departure clearance.
4. Ground Control: Noting that the flight is IFR, receive
taxi instructions.
5. Tower: Pre-takeoff checks complete, receive clearance
to takeoff.
6. Departure Control: Once the transponder “tags up”
with the ARTS, the tower controller instructs the pilot
to contact Departure to establish radar contact.
7. ARTCC: After departing the departure controller’s
airspace, aircraft is handed off to Center, who
coordinates the flight while en route. Pilots may
be in contact with multiple ARTCC facilities; they
coordinate the hand-offs.
8. EFAS/ Hazardous Inflight Weather Advisory Service
(HIWAS): Coordinate with ATC before leaving their
frequency to obtain inflight weather information.
9. ATIS: Coordinate with ATC before leaving their
frequency to obtain ATIS information.
10. Approach Control: Center hands off to approach
control where pilots receive additional information
and clearances.
11. Tower: Once cleared for the approach, pilots are
instructed to contact tower control; the flight plan is
canceled by the tower controller upon landing.
A typical IFR flight, with departure and arrival at airports
without operating control towers, would use the ATC
facilities and services in the following sequence:
1. FSS: Obtain a weather briefing for departure,
destination, and alternate airports, and en route
conditions, and then file a flight plan by calling
1-800-WX-BRIEF. Provide the latitude/longitude
description for small airports to ensure that Center is
able to locate departure and arrival locations.
2. FSS or UNICOM: ATC clearances can be filed and
received on the UNICOM frequency if the licensee
has made arrangements with the controlling ARTCC;
otherwise, file with FSS via telephone. Be sure all
preflight preparations are complete before filing. The
clearance includes a clearance void time. Pilots must
be airborne prior to the void time.
3. ARTCC: After takeoff, establish contact with Center.
During the flight, pilots may be in contact with multiple
ARTCC facilities; ATC coordinates the hand-offs.
4. EFAS/HIWAS: Coordinate with ATC before leaving
their frequency to obtain inflight weather information.
5. Approach Control: Center hands off to approach
control where pilots receive additional information
and clearances. If a landing under VMC is possible,
pilots may cancel their IFR clearance before landing.
Letters of Agreement (LOA)
The ATC system is indeed a system and very little happens by
chance. As a flight progresses, controllers in adjoining sectors
or adjoining Centers coordinate its handling by telephone
or by computer. Where there is a boundary between the
airspace controlled by different facilities, the location and
altitude for hand-off is determined by Letters of Agreement
(LOA) negotiated between the two facility managers. This
information is not available to pilots in any Federal Aviation
Administration (FAA) publication. For this reason, it is good
practice to note on the en route chart the points at which
hand-offs occur. Each time a flight is handed off to a different
facility, the controller knows the altitude and location—this
was part of the hand-off procedure.
