▸Use your FULL callsign (every letter, phonetically) on first contact with a station.
▸Abbreviation is led by ATC: only once the controller shortens your callsign — first letter plus the last two, e.g. G-ABCD → “G-CD” — may you use the short form. Never abbreviate first, and never drop the callsign entirely.
▸Placement: on an initial call the callsign follows the station name (“<station>, <callsign>”); on a read-back it may go at the start or the end.
▸Solo student pilots prefix the callsign with “STUDENT” on initial contact with a unit (CAP 413 §2.35); once acknowledged it need not be repeated.
