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Radiotelephony communications and procedures
Transmissions from aircraft stations operating in Class G airspace are generally of three types. The first is an advisory broadcast (for which an acknowledgement is not expected) when — for traffic separation purposes — a pilot informs the other stations in the vicinity who are listening-out, of her/his whereabouts and intentions. The second type is a station-to-station call, where a pilot requests specific information from the Airservices Australia flight information service, another aircraft station or an aerodrome ground station. The third type is a response to another aircraft or ground station where specific information is supplied in response to a request, or in response to an advisory broadcast when a potential traffic conflict is perceived.
Most transmissions by aircraft in Class G will be made when in the vicinity of non-controlled airfields and usually in the form of broadcasts made in accordance with the requirement (stated in CAR 166C) that pilots 'must make a broadcast ... whenever it is reasonably necessary to do so to avoid a collision, or the risk of a collision, with another aircraft ...' operating in the vicinity. Transmissions to avoid collision, or the risk of a collision, are mandatory. Other broadcasts are discretionary, but their format should conform with a standard broadcast structure.
Note: in the AIP Book, the term 'should' implies that users are encouraged to conform with the procedure, whereas the imperative term 'must' (or 'shall') means that the procedure is mandatory. All procedures/requirements defined as mandatory within AIP are (or should be) supported by CARs or CAOs.
To minimise frequency congestion it is desirable that transmissions are kept to the minimum, both in application and in content, and that 'aviation English' is used. But bear in mind that dissemination of important safety information is vital. Pilots must judge when and what transmissions should be made in the interests of both safe, expeditious traffic flow and minimum frequency congestion. All transmissions must be short but understandable, bearing in mind that Australian idiom may not be comprehensible to all persons receiving the transmission. Be aware the Australian flight training industry attracts many students from overseas and all pilots should do what they can to support that industry and its students.
*Note: the Civil Aviation Regulations define and use the term 'non-controlled aerodrome', however Airservices Australia's AIP book has been erroneously using the USA term 'non-towered aerodrome' for some time (the term is or was also used in some advisory publications) but, as the 'non-towered aerodrome' term is not yet supported by legislation, all references were deleted from AIP or replaced by 'non-controlled aerodrome' effective 21 August 2014.
CARs 166, 166A, 166B, 166C, 166D and 166E establish the regulatory environment for operations at non-controlled aerodromes.
If an aerodrome air traffic control tower does not maintain a 24-hour 7-day service CAR 166D allows CASA to classify any of those aerodromes as a designated non-controlled aerodrome during the periods when the control tower is unmanned. The 'designated' term prescribes mandatory carriage and use of radio on the airfield frequency.
CAR 166C defines the responsibilities and mandatory actions for broadcasting on VHF radio when operating in the vicinity of a non-controlled aerodrome. When planning a flight into an airfield not listed in ERSA, it is advisable to check the frequency being used with the airfield owner/operator — there are unlisted landing areas where a dedicated airfield frequency, other than the multicom 126.7 MHz , may still exist but is not shown on the aeronautical charts; see specific frequencies. This particularly applies to airfields supporting glider operations. CTAFs are usually not monitored by Air Traffic Services.
An aircraft is 'in the vicinity' of a non-controlled aerodrome if it is within a horizontal distance of 10 nautical miles from that aerodrome and at a height above the aerodrome that could result in conflict with operations at the aerodrome. The height dimension of the aerodrome's airspace is a rather nebulous concept — few light aircraft pilots would be familiar with the potential flight path profiles of fast-moving RPT aircraft conducting their normal 'straight-in' or 'circling' approaches or their climb-out; so the upper and lower 'vicinity' limits (at various distances from the airfield with allowance for terrain elevation) are difficult to judge. Perhaps 5000 feet amsl could be regarded as the height limit of the airspace at most CTAF aerodromes – but aerodrome elevation must be taken into account.
The 10 nm radius of the 'vicinity' encloses more than 1000 square kilometres of territory which is likely to contain other airfields, private airstrips (and paddocks) used for recreational operations and agricultural work, any of which may, or may not, appear in ERSA or other airfield guides. When aerodromes are in close proximity they are usually allocated the same CTAF, but that is not always so and only the pilot can judge the best time to make the appropriate frequency changes when operating in the vicinity of more than one landing area.
CAR 166E requires that, if the aerodrome listing shown in ERSA FAC describes the airfield as 'CERT' or 'REG' or 'MIL' or is a 'designated non-controlled aerodrome'*, then the carriage and use of VHF radio — confirmed to be functioning on the designated frequency — is mandatory for all aircraft operating in the vicinity and, of course, the pilot of an RA-Aus aircraft must hold a RA-Aus radio operator endorsement. There are about 300 such civilian certified or registered airfields in Australia, all of which usually have scheduled regional RPT movements. I have compiled a listing in text file format of those CASR Part 139 certified aerodromes  and registered aerodromes  but it will not reflect current status, so check ERSA. Carriage of VHF radio is usually not mandatory within the vicinity of the other non-controlled airfields — unless a temporary notam is current — though highly recommended. But all radio-equipped (hand-held or fixed installation) aircraft must maintain a listening watch and must be prepared to broadcast on the CTAF or the Multicom frequency 126.7 MHz.
*Note: prior to about 2006 'designated non-controlled aerodromes' were commonly known as 'CTAF(R)s'; in the 1990s they were 'MBZs' – mandatory broadcast zones.
CASA have produced two advisory publications to support CTAF procedures and provide guidance on a code of conduct to allow greater flexibility for pilots when flying at, or in the vicinity of, non-controlled aerodromes. These Civil Aviation Advisory Publications (available on this website) are: CAAP 166-1 'Operations in the vicinity of non-controlled aerodromes' (August 2014) and CAAP 166-2 'Pilots responsibility for collision avoidance in the vicinity of non-controlled aerodromes using 'see and avoid' (December 2013).
Note that the 'ultralight' term as used in the CAAPs when recommending a 500 feet circuit height, refers only to those minimum aircraft which have a normal cruising speed below 55 knots, or thereabouts.
CASA has produced an online interactive learning tool titled 'Operations at, or in the vicinity of, non-towered (i.e. non-controlled) aerodromes' which is now available at CASA online learning.
About 100 Australian aerodromes are equipped with an Aerodrome Frequency Response Unit [AFRU] or 'bleepback' — a device that transmits an automatic aural response when a pilot transmits on the CTAF, thus confirming that the pilot is on the correct airfield frequency. AFRU features are explained in AIP GEN 3.4 sub-section 3.4. www.airservicesaustralia.com/publications/aip.asp (click the 'I agree' button to gain entry). To find a particular section of AIP or ERSA you have to click through a number of index pages. The section/subsection/paragraph numbering system was designed for a readily amendable looseleaf print document, so you may find it a little confusing as an online document.
The advantage of Unicom to recreational pilots may be that the service (if it operates on the CTAF) provides some additional information and thereby confirmation of the correct frequency selection and operation of the radio. Unicom communications always take second place to pilot-to-pilot communications on the CTAF.
For recreational aviation the service is similar to a Unicom service but the CA/GRS operator will most likely provide better traffic information. For more details read AIP GEN 3.4 section 3.2. Operating times, call signs and any special procedures will be shown in the aerodrome ERSA entry.
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AIP Book ENR 1.1 section 21 table 'Summary of broadcasts - all aircraft at non-controlled aerodromes'.
The following seven broadcasts are 'recommended', meaning that the operational decisions regarding their use are then properly left to the pilot. The pilot is expected to conduct operations in an airmanlike manner in accordance with the existing environment and traffic conditions. There may be requirements detailed in the ERSA entry for a particular airfield that vary from the standards detailed below. Some temporary variation in the following procedures may also be stipulated, via NOTAM or AIP supplement, for special events; e.g. the annual Birdsville Race meeting or the RA-Aus Easter weekend national fly-in at Temora.
If intending to operate in the vicinity of an aerodrome, rather than land, the aircraft must monitor the appropriate frequency and broadcast:
A turning final broadcast should be regarded as mandatory. It is often difficult to see a stationary aircraft, vehicle or even line marking operators on the runway, let alone an aircraft on a straight-in approach. Most mid-air collisions occur on approach where a faster aircraft descends upon the aircraft in front (see 'Further online reading') and collisions do occur on runways after landing. The turning final call does provide a warning at a time when the aircraft turning is most visible.
The necessity for a turning base or other circuit call are matters of judgement that depend upon the amount and type of traffic, separation and flow. The more ordered it is the fewer the calls needed. On the other hand, if there are no other aircraft heard or seen in the circuit then there will be minimum chance of frequency interference or frequency congestion — and it will be safer — if every possible call is made.
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If you are making a broadcast call where you are asking a question and hope for a response then the called station ID would be "ANY STATION" or "ANY TRAFFIC" preceded by the location name.
The calling station ID is the aircraft call-sign which, for RA-Aus aircraft, already includes the aircraft type. For a General Aviation aircraft the calling station ID is the three-letter aircraft registration, so the aircraft type must be added; e.g. PIPER WARRIOR/ALPHA YANKEE CHARLIE.
In the following example broadcasts the location is 'TANGAMBALANGA' and the aircraft call-sign is 'THRUSTER ZERO TWO EIGHT SIX'.
Aircraft should remain at the runway holding point until all checks are complete and the runway and the approach are seen to be clear — then make the ENTERING RUNWAY broadcast. If there has been a significant delay between the entering runway broadcast and commencement of take-off then a ROLLING call may be helpful to aircraft on the approach. The format would be the same as the entering runway call but with the word ENTERING replaced with ROLLING. If you decide to abandon the take-off after entering the runway then broadcast ABANDONING TAKE-OFF plus your intentions regarding vacating the runway. If you intend taxiing to an exit keep to the left of the runway — just in case!
Some aircraft may report their position in terms of magnetic bearing from the airfield or the VOR radial. Such information is officially acceptable but the compass quadrant format is advisable, being readily understood by all and quite sufficient to alert other aircraft.
Note that the word 'altitude' does not precede 2500; the figures are unlikely to be confused with anything else. Do not precede the altitude figures with the word 'AT' — which is reserved to specify time. When on descent the altitude might be expressed as 'DESCENDING THROUGH (altitude)'; e.g. 'ONE TWO MILES NORTH-EAST / DESCENDING THROUGH FOUR THOUSAND FIVE HUNDRED'. Also note that we have transmitted the location twice, which is always required as there may be several airfields within range on the same frequency, and doubling up the name helps to clarify the transmission. If the airfield name is short, or similar to another airfield within range (say 60 nm), then additional mention of the location may be appropriate; as in the following:
Don't forget aviation times are UTC so the minutes in local time do not coincide with the minutes in UTC when the time difference in the area includes a half-hour — Central (Australia) Standard Time, for example. In such instances it may be advisable to append the word 'ZULU' to the time in UTC minutes — or best use the local time and append the term 'LOCAL TIME' to the message; i.e. 'INBOUND ESTIMATE BOURKE ON THE HOUR LOCAL TIME'.
A 'turning downwind' call could be made when starting the turn onto the downwind leg — if the circuit was joined crosswind or if the aircraft is doing touch-and-goes.
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Requesting informationThere are occasions when a request for information from other aircraft is appropriate. For example, when approaching an airfield and no traffic has been heard on the airfield frequency but you would like to know what runway is in use — possibly by non-radio aircraft. In this case use the call ANY STATION (location) thus:
The informal response from the ground operator might be:
Before taxiing at an airfield with an Unicom or CA/GRS service an information request might take this form:
The response from the ground operator might be:
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Maintaining situation awareness is a must for all pilots. All pilots must be aware of the positions and intentions of all other traffic in the vicinity, and — to determine possible traffic conflicts — able to project the likely movements of such traffic. This is not easy for anyone, particularly so if insufficient information is being provided. This is aggravated when aircraft are conducting straight-in approaches, so extra vigilance must be maintained, remembering the straight-in approach may be on the longest runway rather than the into-wind runway — or it might even be an 'opposite direction' landing.
You must maintain a mental plan of the runways and associated circuit patterns, and overlay that with the current positions and announced intentions of other traffic. You must include the possibility of abnormal events; e.g. where is the missed-approach path for the turboprop aircraft currently on a straight-in approach on the longest runway? And you must keep other traffic informed of your intentions.
Caution. When something unexpected happens in the circuit, for example a broadcast from another aircraft indicates you may be on a collision course, then naturally you will swivel around to locate the other aircraft. In these conditions there is a tendency to be distracted from flying the aeroplane — a dangerous position when at low speed and low altitude, particularly so if turning base or final. See 'Don't stall and spin in from a turn'.
Although a recreational aircraft may have the right of way in a particular traffic situation, it is environmentally positive, courteous and good airmanship for recreational pilots to allow priority to RPT, agricultural aircraft, firefighting and other emergency aircraft, or for that matter any less-manoeuvrable heavy aircraft.
The following is an example transmission from an aircraft on downwind which, after making a downwind broadcast, has monitored a straight-in approach call from an RPT turboprop and is now advising all traffic of the intent to extend its downwind leg and then follow the turboprop in — at a safe interval to avoid wake turbulence.
Class G airspaceThere are no mandatory reports for VFR aircraft operating en route in Class G airspace. Thus after departing the airfield vicinity, such aircraft are only required to maintain a listening watch on the 'appropriate frequency' and announce if in potential conflict with other aircraft — see AIP ENR 1.1 section 44.
"ALL STATIONS (location)" instead of "(location) TRAFFIC" may be used for the called stations ID (refer AIP ENR 1.1 para. 68.4); for example:
So what's the 'appropriate' frequency? This could be:
Class E airspaceAs in Class G there are no mandatory reports for VFR aircraft operating en route in Class E airspace. Such aircraft are only required to maintain a listening watch on the 'appropriate frequency' and advise any potential conflict to the aircraft involved or to ATC. The choice of frequency would be much the same as in Class G with the addition of the appropriate ATC frequency. The latter must be used to take advantage of the Radar Information Service usually available in Class E.
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control zone, but again such information could be a guide to actual weather at other airfields in the vicinity. The availability and frequency of the ATIS is specified in the ERSA airfield data. The continuous information broadcast includes the runway in use, wind direction (degrees magnetic) and speed, visibility, present weather, cloud and QNH. See AIP GEN 3.3 section 2.7. Location information' page and downloading the pdf for the relevant state. The information is also available in the aerodrome facilities section of ERSA and in the ERSA MET section.
The AWIS uses pre-recorded spoken words to broadcast the current observations collected by the AWS — surface wind, pressure, air temperature, dew point temperature and rainfall. (For example, call 08 8091 5549 to hear the AWS aerodrome weather at Wilcannia, NSW.)
In both the ATIS and AWIS reports, wind direction is given in degrees magnetic. This is because they are associated with aerodrome operations where runway alignments are in degrees magnetic, and conformity makes the crosswind estimate easier. Wind direction in all the text-based meteorological reports and forecasts is given in degrees true.
At aerodromes where ceilometer and vismeter sensors are available, the AWIS will report cloud amount, height and visibility but the reliability of such observations is limited — the AWIS broadcasts the aerodrome weather derived from the AWS instrumentation and without any human input. The wind direction is expressed in degrees magnetic to the nearest 10°. Note that some of the VHF frequencies are in the NAV band; i.e. the broadcasts are on the airfield VOR frequency. More information is available in the MET section of ERSA online.
The Flight Information Areas and FIS frequencies are depicted in ERC-L.
An information request to Flightwatch should take the following form — note the Flightwatch operator may be managing quite a number of frequencies so the FIA frequency used (for example 119.4 MHz) must be included in the transmission:
Local QNH of airfields within 100 nm of the route might be acquired from AERIS, ATIS or AWIS; otherwise, area QNH can be obtained from Flightwatch:
'Responsibility of flight crew to see and avoid aircraft
When weather conditions permit, the flight crew of an aircraft must, regardless of whether an operation is conducted under the Instrument Flight Rules or the Visual Flight Rules, maintain vigilance so as to see, and avoid, other aircraft.'
Position information and flight following request call format
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Groundschool — VHF Radiocommunications Guide
| Guide content | Abbreviations and acronyms |
| 1. Transmitter licensing | 2. R/T phrasing | 3. VHF characteristics and radio operation |
| 4. Microair 760 transceiver | [5. R/T procedures] | 6. Safety and emergency procedures |
| 7. Aviation Distress Beacons | 8. Understanding SAR services |
|The next section of the VHF radiocommunications guide outlines safety and emergency procedures|
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