Rules of the Air — Page 118, Lesson 189

We're moving into a new part of the Rules of the Air chapter now — the procedures for when your aircraft is intercepted. This is a serious, high-stakes situation, and the rules here are designed to be absolutely unambiguous, because lives depend on it. Let me set the scene. An interception happens when one aircraft is forced to respond to another aircraft — typically a military aircraft — that has been sent to identify you, guide you, or compel you to change course. The rules we're looking at cover two things: what you do if you can't establish radio contact, and then the exact phraseology you use if you do make contact but don't share a common language. First, the radio failure scenario. If you've been intercepted and you haven't managed to establish contact, the rule says you should, if practicable, repeat your call on the emergency frequency — that's 243.000 MHz. Note that's a different frequency from the standard VHF emergency channel of 121.5 MHz; 243.000 MHz is the UHF military emergency frequency. So the intent is: try to reach them on the channel they're likely monitoring. Then, if your aircraft is equipped with an SSR transponder — that's Secondary Surveillance Radar, the equipment that replies to ground radar interrogations — you must select Mode A, Code 7700, and Mode C, unless the appropriate Air Traffic Services Unit tells you otherwise. Mode A is the transponder's identity mode, and Code 7700 is the universal squawk for emergency. Mode C is the altitude-reporting mode. So you're broadcasting "I am in an emergency" and your pressure altitude, all at once. Now, the second part — and this is the heart of this excerpt — is the situation where radio contact is established, but you and the interceptor don't share a common language. In that case, you use a standardized set of phrases, each with a fixed pronunciation, so that meaning survives even without a shared tongue. Table 6.55 lays this out, and I want to walk you through it carefully, because the pronunciation is as important as the words. Let's start with the phrases used by the intercepting aircraft — the military aircraft giving you orders. First: "Call sign" — pronounced KOL SA-IN — meaning "What is your call sign?" The interceptor is asking you to identify yourself. Then: "Follow" — pronounced FOL-LO — meaning "Follow me." That's an instruction to form up on them. "Descend" — pronounced DEE-SEND — meaning "Descend for landing." Note the meaning is specific: it's not just any descent, it's a descent for the purpose of landing. "You land" — pronounced YOU-LAAND — meaning "Land at this aerodrome." That's a direct order to put the aircraft on the ground at the aerodrome you're over. "Proceed" — pronounced PRO-SEED — meaning "You may proceed." That's the release — you're cleared to continue on your way. And finally, "Hijack" — pronounced HI-JACK — meaning "I have been hijacked." That's the interceptor telling you they've been hijacked, which is a distress signal in itself. Now the phrases used by the intercepted aircraft — that's you, the civilian pilot. These are your responses. "Call sign" — again KOL SA-IN — but here it's your reply: "My call sign is (call sign)." You state your own call sign. "Wilco" — pronounced VILL-KO — meaning "Understood, will comply." That's your acknowledgement that you've received the instruction and you'll carry it out. "Can not" — pronounced KANN NOTT — meaning "Unable to comply." That's your refusal, and it's a critical one — you're telling them you cannot do what they asked. "Repeat" — pronounced REE-PEET — meaning "Repeat your instruction." You didn't understand, so you ask them to say it again. "Am lost" — pronounced AM LOSST — meaning "Position unknown." You're telling them you don't know where you are. "Mayday" — pronounced MAYDAY — meaning "I am in distress." That's the international distress call, and here it's used to declare your emergency state. "Land" — pronounced LAAND — meaning "I request to land at (place name)." You're asking permission to land at a specific place. And "Descend" — pronounced DEE-SEND — meaning "I require descent." You're requesting to descend. Now, one crucial operational rule on top of all this: if you receive instructions from any source that conflict with those given by the intercepting aircraft, you must request immediate clarification — but you keep complying with the interceptor's instructions while you do so. The interceptor's authority is paramount in that moment; you don't stop following their orders just because someone else is telling you something different. And one final note on the table itself: in the second column, the syllables to be emphasized are underlined. So when you see "FOL-LO," the emphasis falls on the first syllable. That emphasis is part of the standard, and it matters for clarity. Let me show you the flight level figures that accompany this section, because they're relevant to the broader rules of the air context. Those figures illustrate the IFR and VFR flight levels up to and including FL, and then above FL — that's the cruising level structure you'll operate within, and it's the framework in which all these interception procedures take place. So, to tie it together: interception is a last-resort enforcement of the rules of the air. Your job as the intercepted pilot is to make yourself identifiable — via the emergency frequency and the transponder — and then, if you can't share a language, to use this fixed phraseology so there's no room for misunderstanding. And remember the hierarchy: the interceptor's instructions win, even if they conflict with others, until you get clarification.