Phraseology — Page 104, Lesson 86

I want to walk you through the phraseology used for Secondary Surveillance Radar, or SSR — that's the transponder-based system that lets air traffic control see your aircraft's identity and altitude on their radar screen. This is a new topic, so we're starting fresh with the standard phrases you'll use and hear. Let's begin with the basic request. When a controller wants you to confirm which Mode A code you've selected on your transponder, they'll say: "CONFIRM SQUAWK (code)". Your reply, if you're already squawking that code, is simply: "SQUAWKING (code)". So "CONFIRM SQUAWK 1234" gets the reply "SQUAWKING 1234". If the controller wants you to operate the IDENT feature — that's the button that makes your blip flash on their screen for identification — they'll say: "SQUAWK IDENT". To ask you to set your transponder to a low sensitivity setting, the phrase is: "SQUAWK LOW". To return to normal operation: "SQUAWK NORMAL". If they need you to temporarily suspend transponder operation — maybe because of interference — they'll say: "SQUAWK STANDBY". That puts the transponder into standby mode, not transmitting. For an emergency, the controller might instruct: "SQUAWK MAYDAY", which means select the emergency code — that's Mode A code 7700. To terminate transponder operation entirely: "STOP SQUAWK". Now, for altitude reporting. To request that you transmit pressure altitude — that's the altitude your transponder gets from the altimeter, reported via Mode C — the phrase is: "SQUAWK CHARLIE". "Charlie" here stands for Mode C. To have you check your altimeter setting and confirm your current level, the controller says: "CHECK ALTIMETER SETTING AND CONFIRM LEVEL". You'd then check your sub-scale setting — the QNH or QFE — and read back your altitude or flight level. If your pressure altitude transmission is faulty — giving wrong indications — the controller will tell you: "STOP SQUAWK CHARLIE WRONG INDICATION". That means deselect the Mode C altitude reporting feature. To request an altitude check — just to verify your level — the phrase is: "VERIFY (level)". For example, "VERIFY FLIGHT LEVEL 350". Your reply confirms that level. If the controller wants to know what type of transponder equipment you have — for example, Mode S capability — they'll ask: "ADVISE THE TYPE OF TRANSPONDER". You might reply with the type, or if you have no transponder at all: "NEGATIVE TRANSPONDER". For departure, the controller will assign a code: "FOR DEPARTURE SQUAWK (code)" or simply "SQUAWK (code)". That means set your Mode A to that code. If they need you to reselect a different mode and code — maybe you set the wrong one — they'll say: "RESET (mode) (code)", and you reply: "RESETTING (mode) (code)". For Mode S equipped aircraft — those with the more advanced transponder that can transmit your aircraft identification — the controller might ask: "RESET MODE S IDENTIFICATION", meaning reselect your aircraft's registration or call sign in the transponder. Now, let me summarise the key phrases and their meanings in a clear table for you: - SQUAWK (code) — Set the Mode A code as instructed. - CONFIRM SQUAWK — Confirm the Mode A code set on the transponder. - SQUAWK IDENT — Operate the IDENT feature. - SQUAWK MAYDAY — Select emergency code (7700). - SQUAWK STANDBY — Select the standby feature. - SQUAWK CHARLIE — Select pressure altitude transmission feature (Mode C). - CHECK ALTIMETER SETTING AND CONFIRM LEVEL — Check your pressure setting and confirm your present level. - STOP SQUAWK CHARLIE WRONG INDICATION — Deselect pressure altitude transmission because of faulty operation. - VERIFY LEVEL — Check and confirm your level. This is used to verify the accuracy of the Mode C derived level information displayed to the controller. - CHECK ID SQUAWK — For a Mode S equipped aircraft, check the setting of the aircraft identification feature. Finally, note that the pilot's reply to SSR instructions is usually an acknowledgement or a readback. So if the controller says "SQUAWK 1234", you'd read back "SQUAWKING 1234". If they say "SQUAWK IDENT", you'd acknowledge "SQUAWK IDENT" or simply operate the feature and say "IDENT". There's also a note in the book that other phraseologies for area control radar service are given in the section containing approach control radar service phraseologies — so we'll cover those when we get there.