Call Signs and Transfer of Communication

Station call signs

An aeronautical station is identified by the name of the location and the unit or service available, in that order: the place, then what it does. The suffix table is fixed by Annex 10:

CONTROL for an area control centre, APPROACH for approach control, with ARRIVAL and DEPARTURE for approach control radar arrivals and departures;

TOWER for aerodrome control, GROUND for surface movement control, DELIVERY for clearance delivery, APRON for apron control;

RADAR for radar in general and PRECISION for a precision approach radar;

HOMER for a direction-finding station, tying back to the bearing service of the first lesson;

INFORMATION for a flight information service, DISPATCH for company dispatch, and RADIO for an aeronautical station.

Once satisfactory communication has been established, the name of the location or the unit/service may be omitted; that is the rule behind the tower answering simply as the location name after first contact.

Aircraft call signs: the three types

An aircraft radiotelephony call sign is one of three types, and Annex 10's own examples carry the whole scheme:

Type a — the characters of the registration marking, which may be preceded by the name of the aircraft manufacturer or model: N57826, or CESSNA FABCD.

Type b — the telephony designator of the operating agency followed by the last four characters of the registration: VARIG PVMA.

Type c — the telephony designator followed by the flight identification: SCANDINAVIAN 937, the shape airline flying runs on.

Abbreviating, and when you may

The abbreviated forms are: for type a, the first character of the registration plus at least the last two characters, with the manufacturer or model name allowed in place of the first character; for type b, the designator plus at least the last two characters; and for type c, no abbreviated form exists. Abbreviation is permitted only after satisfactory communication has been established, provided no confusion is likely, and an aircraft uses its abbreviated call sign only after the aeronautical station has addressed it that way first.

Full call signs always open communication — the calling procedure names the station called, then the station calling; the reply reverses it, and that reply is the invitation to proceed.
Clearances always carry the call sign — when issuing an ATC clearance and when reading it back, controllers and pilots always add the call sign of the aircraft concerned.
After contact is established, continuous two-way communication is permitted without further identification until the contact ends.
No transmission during take-off, the last part of final approach or the landing roll, except for reasons of safety: those seconds belong to the flying.

HEAVY, SUPER, and borrowed names

Two decorations attach to the call sign. Aircraft in the heavy wake-turbulence category say HEAVY, and the very largest say SUPER, immediately after the call sign on the initial call to each ATS unit, warning everyone on frequency about the wake. The categories themselves belong to the flight-planning course, which also sets out the ICAO flight plan: item 7 carries the call sign, and item 9 the wake category.

And the call sign can be borrowed against confusion. An aircraft may not change the type of its call sign in flight, except temporarily on ATC instruction in the interests of safety: when two similar call signs share a frequency, ATC transmits "change your call sign to (new call sign)", and restores the original with "revert to flight plan call sign", the call sign of flight-plan item 7, at a stated point or when the confusion has passed.

Transfer of communication

Frequencies change hands under a simple two-sided rule:

By the ground station — the aeronautical station advises the aircraft to transfer to the next frequency, in accordance with agreed procedures: the everyday "contact..." hand-off.
By the aircraft — in the absence of such advice, the aircraft notifies the station before transferring: nobody simply vanishes from a frequency.

On the HF networks the same rule grows procedure around it: a transfer between networks happens preferably while in contact with a station working in both; the aircraft is advised of the primary and secondary frequencies to use; on entering a network after take-off it transmits its take-off time or the time over the last check-point, and on entering a new network the time over the last check-point or its last reported position; and it leaves a network with a stated farewell, "changing to" the ATS unit concerned, or "landed" with location and time.

Station call signs

Aircraft call signs: the three types

Check you understood

Abbreviating, and when you may

HEAVY, SUPER, and borrowed names

Transfer of communication

What the exam asks