RADIO COMMUNICATIONS FACILITIES
When piloting an airplane, you have frequent need to make two-way radio contact with various facilities. Among these facilities are Flight Service Stations, terminal and enroute Air Traffic Control, and local airport UNICOM and traffic. Also, there is need for one-way (listen only) contact with broadcast facilities such as ATIS, AWOS, and HIWAS. Information on communications is scattered throughout FAA publications and is sometimes hard to find. This treatise addresses all these types of communications here in one place, including references to avoid excessive replication of published material.
The various types of communications links can be broadly categorized into two categories: direct links and remote links. In the former, you communicate directly between the radio in your airplane and a radio located at the facility you are talking to (such as an ATC tower). In the latter, you communicate between the radio in your airplane and a radio located remote from the facility you are talking to, but which is closer to your location. A remote link is an unmanned radio site that is connected by landline, microwave, or other means to the facility that may be hundreds of miles away.
The Airport/Facility Directory (A/FD) has a summary of communications frequencies and other communications information in the Directory Legend under Communications.
Over a direct radio link, you talk to a person over a radio located at their facility.
There are many ways to contact a flight service station over the radio. The FSS will have radios located at their facility which are useful for contacting them directly within several tens of miles while airborne and from the local field when on the ground. Frequencies for these local radios are published on sectional charts in the FSS data block associated with the field where the FSS is located. In addition to the frequency(ies) shown on the FSS data box, frequencies 121.5 (emergency) and 122.2 are available at all (most?) Flight Service Stations. The Airport/Facility Directory (A/FD) lists direct FSS frequencies in two places: in the listing for each airport, and in a separate section called ARTCC/FSS. In the airport listing for the field where the FSS is located, it lists the direct communications (not through any remote) frequencies available on the field. In the ARTCC/FSS section, it lists the direct on-field frequencies plus all the remote frequencies and locations.
Another FSS direct frequency is 123.6 when the FSS provides Local Airport Advisories for the field on which it is located (AIM 4-1-9). This might be on 123.65, but usually 123.6. If the field has a part-time tower, the LAA will usually used the tower frequency when the tower is closed.
Flight Watch
Or,
more formally, Enroute Flight Advisory Service, EFAS. See AIM 7-1-4. This is
universally available on 122.0 via RCOs linked back to certain FSSs. There are some additional frequencies
available for high altitude aircraft, but lowfliers use 122.0. In the inside back cover of the A/FD there
is a map showing the locations of the RCOs.
To
call Flight Watch, you are supposed to use the name of the Center (ARTCC)
responsible for the airspace you are in, such as “Memphis Flight Watch, N12345,
Rocket VOR”, giving the name of the VOR or other navaid nearest you so they
know how to choose the best RCO. So how
do you know which Center handles your airspace? Not so easy for the VFR pilot.
On IFR enroute charts, Center boundaries are depicted, but they don’t
show up on VFR charts. You can usually
tell using the map on the inside back cover of the A/FD. But, if you don’t know, don’t worry about
it. Just call “Flight Watch, N12345,
Rocket VOR”. The one responsible for
the airspace around the navaid you specify will respond, giving their
name. The other ones that may be able
to hear you won’t know the navaid and won’t respond, or will know the navaid
and will know it’s not theirs. If you
really want to know which Center is responsible, you can call up a nearby
terminal ATC facility on the radio and ask, or call an FSS and ask.
UNICOM
See
AIM 4-1-11. UNICOMs are always
communicated with directly, no remote relays.
There are seven frequencies that can be assigned to UNICOM stations at
untowered fields. Where there is a
tower, or on-field FSS, the UNICOM is 122.95.
UNICOM frequencies are shown on sectional charts and in the A/FD.
Common
Traffic Advisory Frequency (CTAF)
At a towered field with full-time tower, no CTAF exists. Where there is a part-time tower, the tower frequency is usually used as the CTAF when the tower is closed. Where there is no tower but there is an on-field FSS, the CTAF is usually on 123.6 and the FSS provides Local Airport Advisory service on that frequency (AIM 4-1-9). Where there is no tower or FSS but there is a UNICOM (usually at an FBO), the CTAF is the same as the UNICOM frequency.
These airport and weather broadcast stations operate on frequencies published on sectional charts and the A/FD. Sometimes the information is broadcast over a navaid as discussed below under Voice Over Navaid.
There are several types of remote communication facilities. All provide a means for a pilot to contact an ATC controller or FSS specialist when the pilot is located a considerable distance, perhaps hundreds of miles, from the facility where the controller or specialist is located. Some of these remote links are completely transparent and cannot be distinguished from a direct communication link. Others require use of special procedures.
Some of these remote links are exactly the same to a user but go by different names. A Remote Communications Outlet (RCO) connects to a Flight Service Station. A Remote Transmitter/Receiver (RTR) connects to a terminal ATC facility (TRACON, or approach control). A Remote Center Air/Ground (RCAG), or Remote Communications Air/Ground, connects to an ARTCC. In any of these cases, the pilot is given a frequency and the communications proceeds exactly as if the communication link was direct to the remote facility. No consideration need be given to the fact that it is a remote link.
Here’s the FAA word on RCOs, from the P/CG:
REMOTE COMMUNICATIONS OUTLET- An unmanned communications facility remotely controlled by air traffic personnel. RCO’s serve FSS’s. RTR’s serve terminal ATC facilities. An RCO or RTR may be UHF or VHF and will extend the communication range of the air traffic facility. There are several classes of RCO’s and RTR’s. The class is determined by the number of transmitters or receivers. Classes A through G are used primarily for air/ground purposes. RCO and RTR class O facilities are nonprotected outlets subject to undetected and prolonged outages. RCO (O’s) and RTR (O’s) were established for the express purpose of providing ground-to-ground communications between air traffic control specialists and pilots located at a satellite airport for delivering en route clearances, issuing departure authorizations, and acknowledging instrument flight rules cancellations or departure/landing times. As a secondary function, they may be used for advisory purposes whenever the aircraft is below the coverage of the primary air/ground frequency.
And here’s what the P/CG says about RCAGs:
REMOTE COMMUNICATIONS AIR/GROUND
FACILITY- An unmanned VHF/UHF transmitter/receiver facility which is used to
expand ARTCC air/ground communications coverage and to facilitate direct
contact between pilots and controllers. RCAG facilities are sometimes not
equipped with emergency frequencies 121.5 MHz and 243.0 MHz.
The AIM says of RCAGs:
5-3-1. ARTCC Communications
a. Direct
Communications, Controllers and Pilots.
1. ARTCC’s
are capable of direct communications with IFR air traffic on certain
frequencies. Maximum communications coverage is possible through the use of
Remote Center Air/Ground (RCAG) sites comprised of both VHF and UHF
transmitters and receivers. These sites are located throughout the U.S.
Although they may be several hundred miles away from the ARTCC, they are
remoted to the various ARTCC’s by land lines or microwave links. Since IFR
operations are expedited through the use of direct communications, pilots are
requested to use these frequencies strictly for communications pertinent to the
control of IFR aircraft. Flight plan filing, en route weather, weather
forecasts, and similar data should be requested through FSS’s, company radio,
or appropriate military facilities capable of performing these services.
A Ground Communication Outlet (GCO) is a different kind of facility, used to connect a pilot on the ground to either an ATC facility or to a FSS. From the Pilot/Controller Glossary:
GROUND COMMUNICATION OUTLET (GCO)- An
unstaffed, remotely controlled, ground/ground communications facility. Pilots
at uncontrolled airports may contact ATC and FSS via VHF to a telephone
connection to obtain an instrument clearance or close a VFR or IFR flight plan.
They may also get an updated weather briefing prior to take-off. Pilots will
use four “key clicks” on the VHF radio to contact the appropriate ATC facility
or six “key clicks” to contact the FSS. The GCO system is intended to be used
only on the ground.
They don’t tell you one critical little secret. You need to use “long clicks” to make the GCO work. It won’t respond to the kind of short clicks you are used to using to activate Pilot Controlled Lighting. Press the radio mike button for one second, release it for one second, repeat for the desired number of clicks. The GCO will then respond with an automated voice telling you that it is dialing the Center or the FSS, then the Center or the FSS will answer the phone, identifying themselves, then the conversation proceeds exactly as if you both were on the radio. At least, that’s how it worked at the only one I’ve ever encountered.
Voice-equipped en route radio navigational aids are under the operational control of either an FAA Automated Flight Service Station (AFSS) or an approach control facility. These navaids with voice are identified on sectional charts by having no underline under the navaid frequency and by having frequency(ies) listed on top of the navaid information box. To communicate over one of these voice-equipped navaids, you listen on the navaid frequency using your nav radio, and transmit on the frequency listed on top of the box with an “R” after it.
In addition to the navaid having the capability of transmitting voice from FSS or ATC, it may also have a regular RCO collocated with it. If so, there will be one or more frequencies without an “R” listed on top of the box. Such frequencies are two-way frequencies with no navaid involvement.
The voice-over-navaid remote communications capability of the navaid should not be confused with the voice broadcast capability of some navaids which can be used for disseminating ATIS/AWOS, HIWAAS, and TWEB information. A navaid with voice broadcasts of this type, but with no voice communications capability on the navaid frequency, will have an underline under the navaid frequency.
See AIM 1-1-13 and 4-2-3.
© 2001 Stanley E. Prevost All Rights Reserved Worldwide.