Now, who gets to start the abbreviation — Page 66, Lesson 49

I want to walk you through the proper use of abbreviated call signs in aviation communications, using the example of Scandinavian 937 as our reference. Let's start with the fundamental rule: abbreviated call signs shall only be used after satisfactory communications have been established and provided no confusion is likely to arise. This means you cannot abbreviate your call sign on the very first call to a new controller — you must first establish a clear working relationship, and even then, only if there's no risk of being mistaken for another aircraft on the frequency. Now, who gets to start the abbreviation? Only air traffic control may initiate abbreviation of aircraft call signs. As a pilot, you cannot decide on your own to shorten your call sign. Once ATC has abbreviated it, you as the pilot may then use that abbreviation in your replies. However, there's an important limitation: if you change to another station — for example, switching from one controller to the next sector — you must revert to the full call sign until that new controller also initiates abbreviation. The book gives us three types of call signs. Let me explain each one clearly. Type A call signs are those that begin with a registration mark — for example, G-BTRY. The abbreviation takes the first character plus at least two last characters. So "G-BTRY" becomes either "G-RY" or "G-TRY". Notice the pattern: you keep the first letter, and then you keep at least the last two letters of the original call sign. You have some flexibility — you can keep two or three of the last characters. There's also a special note for Type A: either the name of the aircraft manufacturer or the aircraft model may be used in place of the first character. So instead of saying "G-BTRY", you could say "Piper G-BTRY", and the abbreviation would become "Piper RY" or "Piper TRY". The manufacturer or model name replaces the registration prefix letter. Type B call signs are those that use an operating agency designator — for example, "SPEEDBIRD ABCD". The abbreviation takes the operating agency designator followed by at least two last characters. So "SPEEDBIRD ABCD" becomes "SPEEDBIRD CD" or "SPEEDBIRD BCD". You keep the airline name or company designator, and then add at least the last two letters of the flight identifier. Type C call signs have no abbreviation. These are typically numeric call signs, like "Scandinavian 937". You cannot abbreviate them — they must always be used in full. Let me give you the specific examples from the book so you can see how this works in practice. For Type A, the full call sign "N57826" abbreviates to "N26" or "N826". "CESSNA FABCD" abbreviates to "CESSNA CD" or "CESSNA BCD". "CITATION FABCD" abbreviates to "CITATION CD" or "CITATION BCD". For Type B, "VARIG PVMA" abbreviates to "VARIG MA" or "VARIG VMA". For Type C, "SCANDINAVIAN 937" has no abbreviated form. You always say the full call sign. Now, let me shift to a related topic that appears in this excerpt — Q codes. Q codes were originally developed when much of communication work, especially on HF long range, was done in Morse code. They were quicker to key in than spelling out entire phrases. For example, "QNH" was much faster to send in Morse than "ALTIMETER SETTING SEA LEVEL PRESSURE". Today, some Q codes are still widely used because they remain useful abbreviations. Importantly, they are spoken in plain English, not phonetically. You don't say "Quebec November Hotel" — you just say "Q-N-H" as three letters. The excerpt gives us two commonly used Q codes. QFE means atmospheric pressure at aerodrome elevation. This is the pressure setting that, when set on your altimeter, will read zero feet when you're on the ground at that aerodrome. QNH is also listed, though its full meaning is cut off in this excerpt — but you already know from earlier lessons that QNH is the pressure setting that gives you altitude above mean sea level when set on your altimeter. Let me show you the diagram that illustrates pressure settings, which will help tie these concepts together. This figure shows examples of pressure settings, including QNH and QFE, so you can visualize how they relate to your altimeter readings. And here's another diagram showing special weather conditions that might affect your use of these pressure settings. To summarize what we've covered: abbreviated call signs can only be used after communications are established and no confusion will arise. Only ATC initiates the abbreviation. Type A uses the first character plus at least two last characters, Type B uses the operating agency plus at least two last characters, and Type C — like Scandinavian 937 — has no abbreviation. Q codes like QFE and QNH are useful abbreviations spoken in plain English, with QFE being the atmospheric pressure at aerodrome elevation.