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Flight Service Station Uhf Frequency Assignments

Many student pilots--and some veteran aviators--are intimated by radio communications. What if I choose the wrong frequency? How can I better understand the rapid-fire numbers?
Errors in communication are common, even for professional pilots. At least once a week I hear a pilot communicating on the wrong frequency, and sometimes that pilot is me. Many aircraft have two communication radios, and a common error is to enter a new frequency on one radio, then attempt to transmit on the other radio--which is not tuned to the desired frequency. Pilots can establish a plan that lessens this possibility.
Using that second radio

The second radio is in your aircraft primarily as a backup. Because aircraft radios are very reliable, however, you should find that both are working. When that's the case, assign one radio to communications while in the air, and the second radio to on-the-ground and auxiliary information uses. Think of the radio higher on the panel as the in-air radio, and the lower radio as ground-based. Specifically, the number-one radio is for takeoff (tower or common traffic advisory frequency), departure, en route, approach, and landing frequencies. The second radio is assigned clearance, ground, weather (ATIS, ASOS), and flight service duties--remember to monitor the emergency frequency (121.5 MHz) when you're not using the second radio.

Incorrect frequencies can be entered by pilots--or provided by controllers during a handoff--so radios with flip-flop frequencies are particularly useful. With the press of a button, the pilot can quickly return to the prior frequency if communications are not possible on the new frequency. Once communication is established on the new frequency, experienced pilots enter the next expected frequency--before they're asked to switch. Some sequences are obvious; departing a towered airport the sequence is always ATIS, clearance, ground, tower, and departure. You will develop this skill over time. Listening to how other aircraft are handed off also provides hints.

Even for local flights, the pilot should know necessary and likely frequencies before entering the cockpit. Reviewing frequencies should be a routine part of preflight planning. You are less likely to make a mistake if you've already reviewed the possibilities.

If your aircraft has two older radios without standby frequencies, use the radios alternately. Enter new frequencies directly on the unused radio. When it is time to change frequencies, use the audio panel to switch to the other radio. Again, it is easy to return to the old frequency if necessary, and an anticipated frequency can be entered in advance.

Weather on the fly

Let's say you need weather information while you're flying. The primary source is from a flight service station (FSS), and all stations answer the common frequency 122.2 MHz. However, there are two problems using this frequency--it can be congested, and several stations may answer your call. Include your location and the name of the FSS you are addressing on the initial call. Address FSS as "radio": "Cleveland Radio, Cirrus Seven-Six-Two-Lima-Charlie, over Zanesville VOR, over." In most cases, you should not include a specific request until two-way communications are established. The word "over" indicates the end of your transmission and that you expect a reply.

Flight service stations can direct their replies through several antennas, and will choose one closest to your stated location. If you do not specify your location, the station must reply over all its antennas. This floods the frequency to the detriment of the system.

You may blindly call to any station, "Any radio, Cessna Four-Four-Six-Fife-Golf...." However, a request directed to the closest station is preferable as communications will be clearer: "Indianapolis Radio..." Aeronautical charts will indicate the correct FSS. Flight service specialists are certified as competent in their local areas. While any specialist can provide an answer by referring to a computer, a local specialist should know more about smaller airports, local procedures, and local weather patterns.

You can choose dedicated FSS frequencies other than 122.2 MHz. One advantage is less congestion, and the call is directed to one FSS only. Refer to your sectional chart.

Other options

There are other outlets for weather information. The En Route Flight Advisory Service, called Flight Watch, on 122.0 MHz is often helpful. However, in marginal weather this frequency may be busy, and a call to a specific FSS may get a quicker reply. Also, only weather is supposed to be discussed on 122.0; use another frequency if you need information on airports, airspace, notams, or temporary flight restrictions.

Engaging in two-way conversations with flight service or Flight Watch may not even be necessary. Sometimes simply monitoring conversation on 122.0 MHz or other FSS frequencies will answer your questions. Regional weather, transcribed weather en route broadcasts (TWEBS), and--particularly--significant weather advisories (sigmets) are available as recorded messages over certain VORs as indicated on charts. These same VORs and others serve as transmission sites for FSS.

Another alternative is to call FSS on 122.1 MHz: "San Diego Radio, Diamond Tree-Four-Fife-Four-Hotel, listening over the X-ray Yankee Zulu VOR, over." The station will respond on the VOR frequency. Before establishing communication though a VOR, make sure it's tuned to the correct frequency. Listen to the Morse code identifier, which confirms the VOR--and that you will hear the FSS specialist's reply. Most aircraft radios include a filter that allows the pilot to remove or substantially mute the Morse code, making voice communications more audible.

Of course, weather information can be accessed on ATIS and ASOS frequencies. While we often focus on broadcast weather at our destination, local weather also is available at many airports along our route.

If you are receiving air traffic control (ATC) services and communicating with an ATC facility, and want to obtain weather or other information, you have two choices. The simplest is to ask ATC for permission to leave the frequency: "Boston Center, Cessna Fife-Four-Golf would like to leave the frequency for a moment." ATC may ask you return within a specific number of minutes or miles, if you are likely to leave the controller's airspace in the interim. However, many pilots learn to juggle two frequencies at the same time--monitoring one while transmitting and receiving on a second. As long as the first frequency is relatively quiet, this is not a chore. However, when communications are simultaneous, it can be hard to separate the two. One trick is to set volumes at different levels; your brain can then better separate what you are hearing from the two sources.

Making sense of the numbers

Several hints can help you to sort out frequencies. All aviation communication, VOR, and ILS frequencies are in the 100 MHz band, so the first number is always "1." The hundredths digit can be only 0, 2, 5, or 7; 1xx.x2 implies 1xx.x25; and 1xx.x7 implies 1xx.x75--when a frequency is assigned, the ending "5" is often omitted. Trailing zeros in the hundreds and thousandths positions are always omitted in voice transmissions. Valid frequencies in-clude 109.97, 135.75, 129.425, 123.0, 133.77, and 129.3 MHz.

All ATC communications are between 118.0 and 137.0 MHz. If you think you're given a frequency above or below those numbers, there is a mistake.

FSS frequencies are all in the 122 and 123 MHz series; for example, 122.25, 122.3, 122.35, 122.45, 122.55, 122.6, 122.65, and 123.65 MHz. Remember the universal FSS frequency of 122.2 MHz, and that Flight Watch is 122.0.

All FAA facilities monitor the emergency frequency, 121.5 MHz. ATC may ask you to monitor 121.5 to help locate an activated emergency locator transmitter.

If you wish to talk to the pilot of another airplane, use the air-to-air frequency of 122.75 MHz. It is not considered good etiquette to fill other frequencies with pilot-to-pilot chats.

VOR frequencies are between 108.0 and 117.975 MHz, immediately below aviation communication frequencies beginning at 118.0.

When communicating in the pattern of an airport without an operating control tower, the common traffic advisory frequency (CTAF) is used. However, the correct frequency may not be explicitly noted on charts. If the airport has a control tower but the tower is closed for the night, the tower frequency usually becomes the CTAF. At nontowered airports, a unicom frequency is used. Typical unicom frequencies are 122.7, 122.72, 122.8, 122.97, 123.0. 123.05, and 123.07 MHz.

At controlled airports, ground frequencies are likely 121.3, 121.5, 121.7, and 121.9. Note that all begin with 121 and end in an odd tenth. Tower controllers take advantage of this by using a clipped communication, "Cirrus Fife-Hotel-Juliet, contact ground on point seven clearing the runway." They expect you to know they mean 121.7.

A device for understanding radio communications is knowing ahead of time what you are likely to hear. This information should improve your recognition of the correct frequency, and sharpen your communication skills.

Dr. Ian Blair Fries is a CFI, senior aviation medical examiner, and ATP, and holds a Lear 35 type rating. He serves on the AOPA Air Safety Foundation Board of Visitors and is cochairman of the AOPA Board of Medical Advisors.

Want to know more?
Links to additional resources about the topics discussed in this article are available at AOPA Flight Training Online.

Related Articles

A flight service station (FSS)[1] is an air traffic facility that provides information and services to aircraft pilots before, during, and after flights, but unlike air traffic control (ATC), is not responsible for giving instructions or clearances or providing separation. They do, however, relay clearances from ATC for departure or approaches. The people who communicate with pilots from an FSS are referred to as flight service specialists.

The precise services offered by stations vary by country, but typical FSS services may include providing preflight briefings including weather and notices to airmen (NOTAMs); filing, opening, and closing flight plans; monitoring navigational aids (NAVAIDs); collecting and disseminating pilot reports (PIREPs) and airport surface weather observations; offering traffic advisories to aircraft on the ground or in flight; relaying instructions or clearances from air traffic control; relaying information from or about airborne aircraft to their home bases, military bases or homeland security, providing weather advisories to aircraft inflight, initiating search and rescue on missing VFR aircraft, and providing assistance in an emergency. In many countries, flight service stations also operate at mandatory frequency airports to help co-ordinate traffic in the absence of air traffic controllers, and may take over a control tower frequency at a controlled airport when the tower is closed.[2]

In most cases, it is possible to reach flight service stations either by radio in flight, or by telephone on the ground. Recently, some countries, such as Canada and the United States, have been consolidating flight services into large regional centres, replacing former local flight service stations with remote communications outlets (RCOs)[3] connected to the centres.

Flight services in different countries[edit]

Flight services in the United States[edit]

As of 2005, the FAA federal contractor for their flight service function throughout the continental U.S., Hawaii and the Caribbean was Lockheed Martin (LMFS).[4]Leidos has taken over as of 17 August 2016, following a merger with Lockheed Martin Information Systems & Global Solutions Business.[5] The FAA still oversees flight service in Alaska. At this time Leidos operates three large hub facilities and one smaller satellite facility. Flight service duties and responsibilities are divided into preflight, inflight and flight data.[6] They also monitor the HIWAS and TIBS recorded weather briefings, which pilots can access via radio or phone. The services are provided at no charge to the flying public.

Preflight – Primarily responsible for filing flight plans, giving preflight weather briefings, and providing information concerning air traffic, they also take information from pilots coming into the US to notify the United States Customs Service that an aircraft is inbound. The Leidos call tree has the ability to route calls to any flight service facility in the country.[7]

Inflight – which the pilots call “Radio”, activates, cancels, and alters VFR flight plans. They take position reports and changes of destination for both civilian and military aircraft. They relay IFR and SVFR clearances to aircraft on the ground either by phone or through their frequencies when there is no direct method of communication with the air traffic control facility governing the area. At border stations, Radio also takes information from aircraft crossing into the U.S., and issues squawk codes to VFR aircraft which identify them to Homeland Security’s radar. They relay information on forest fires to the U.S. Forest Service. Inflight monitors VHF and UHF frequencies, VOR voices, and emergency frequencies – from 60 to 100 different frequencies per area. The United States FSS radio frequencies are published in several FAA publications, including airport facility directories (AFD), VFR sectional maps, and IFR low and high altitude en route charts. When pilots have an inflight emergency, such as being lost, having smoke in the cockpit, or having low fuel and needing directions to the nearest airport with fuel, they call flight service for assistance.

Radio can take flight plans and give pre-flight briefings over the radio in extenuating circumstances.[8]

Leidos until early 2016 had another inflight position called Flight Watch, which was dedicated to updating weather for aircraft en route. Radio now performs that function. Enroute Flight Advisory Service (EFAS) or Flight Watch was designed to give pilots who are already airborne updates on weather during their current flight, and take pilots' reports or PIREPS, which they enter into the computer for transmission to the National Weather Service.[9]

The Flight Data position in flight service is an informational clearinghouse that pilots seldom speak to unless they are calling for an IFR clearance by telephone. Flight Data is responsible for coordination with other air traffic facilities, U.S Customs and Homeland security, the Fire Service, military baseops, airport managers and law enforcement.

Search and rescue activities are initiated at Flight Data when VFR aircraft become overdue. Weather observers and airport tower operators call them to input weather observations or pilot reports to the National Weather Service. LMFS added an option for pilots in 2013 called Surveillance Enhanced Search and Rescue, SE-SAR,[10] which allows them to keep track of en route aircraft via satellite. Flight Data issues some types of Notices to Airmen (NOTAMs) through the FAA's E-Notam II computer system.[11]

Flight services in Canada[edit]

Main article: Flight Information Centre

In Canada, Flight Information Centres (FIC) monitor the FISE frequencies (frequency 126.7 MHz is for broadcasts) as well as 121.5 MHz, the emergency frequency. However, Canadian FIC have phased out the use of 126.7 MHz for FISE (en route flight information) and are instead utilizing discrete frequencies. This is to decrease the frequency congestion often experienced on 126.7. These frequencies are found in the Canada Flight Supplement (CFS).

Unlike in the United States, even for VFR flights, pilots are required to file a flight plan or have a flight itinerary with a responsible person for any flight greater than 25 nm from the departure aerodrome.[12] Also, in Canada, flight plans are opened automatically at the estimated time of departure (ETD). Flight information centres play a prominent role managing flight plans, collecting position reports from pilots en route, and initiating commsearch procedures to locate pilots who have not closed flight plans.

There is no per-use charge for flight services, but aircraft owners are required to pay Nav Canada a daily or annual fee, depending on aircraft weight, to support all air traffic services, both FSS and air traffic control (for a light private aircraft, the fee is approximately CAD 70/year). Foreign light aircraft entering Canada are billed a quarterly fee.[13]

Canada has many mandatory frequency airports, which have enough traffic to justify special rules, but not enough to justify a control tower. Many of these airports have an onsite FSS that pilots are required to contact, while others have Remote Aerodrome Advisory Services (RAAS) provided by an FSS in a different location. Rarely, an airport will have Mandatory Frequency Area rules, but no ground station.

Until 1996, the Canadian federal government operated all air traffic services (FSS and air traffic control) through Transport Canada, a government department. Currently, a private non-profit corporation, Nav Canada, operates both FSS/FIC and air traffic control and has significantly modernized the system, which involved the closing of some local FSSs. However, the company in turn created six large Flight Information Centres (FICs) situated at airports in Halifax, Quebec City, London, Winnipeg, Edmonton and Kamloops. These provide standard en route flight services (weather briefing, flight-planning and commsearch). FSSs provide airport advisories, vehicle control, weather observations, clearance delivery, emergency assistance, and some provide Remote Aerodrome Advisory Services. FSSs are responsible for the safe and efficient movement of aircraft on manoeuvering areas and within their designated control zone. Most FSS stations are open 24/7; some have limited hours. They are no longer responsible for flight planning, except for sending departure and arrival messages to the appropriate FIC. The FICs have assumed the responsibility for flight plans, filing, in-flight alerting, flight plan closures, interpretive weather briefings and NOTAM (NOtices To AirMen) management. The FICs also have large areas they are overseeing and have networks of RCOs, some of which are co-located with FSS or air traffic control sites. The FICs are similar in function and scope to the FAA's former automated FSS system in the United States. North Bay FIC is tied into the North American Aerospace Defense Command (NORAD) North Warning System (NWS) radar system, and has a network of 23 RCOs located across Canada's Arctic coast. Quebec City, North-Bay and Kamloops FIC also assist and oversee the "Community Aerodrome Radio Station" (CARS) program.


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