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I heard a pilot replied "CC" to ATC instruction.

I can't remember the exact situation, but does anyone knows what it means?

mins
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Jihoon
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5 Answers5

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Short answer

Charlie-Charlie is a fancy substitution for a standard affirmative.

It comes from the convention of abbreviating Correct/Yes by letter C in codes. It was early standardized and used at sea since 1857. Under the Commercial Code of Signals (1857-1902), the C flag, in addition of representing the letter itself, had the meaning of Yes/Affirmative.

enter image description here
C flag meaning affirmative

This code has been improved and extended into the International Code of Signals (ICS). While the visual representation changed, the meaning was preserved extended to radiocommunications. From the 2003 ICS:

Signals for flags, radiotelephony, and radiotelegraphy transmissions.
C: Affirmative—YES or “The significance of the previous group should be read in the affirmative”.

Examples

Discovered by @ymb1, this accident investigation report, for a Boeing 747 accident in 1987, includes a transcription of the pilot (CA) controller (MA) exchange:

  • CA: Roger, we will appreciate it if you can alert, er, fire, er, er, er.
  • MA: Do you request a full emergency please? A full emergency?
  • CA: Affirmative, that's Charlie Charlie
  • MA: Roger, I declare a full emergency.

later:

  • MA: Confirm runway one four?
  • CA: Charlie Charlie.

And this other document, still from @ymb1:

  • Do you have ATIS information Delta?
  • Charlie Charlie we have Delta.

...

  • Ok our stand 41 AF028.
  • Understand B 41.
  • Charlie, charlie.
mins
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    Formally, "roger," "wilco," and "affirm/affirmative" are not synonyms. "Roger" means "I understand," "wilco" means "I will comply," and "affirmative" means "yes." Usage does differ from the formal meaning, however. – Wayne Conrad Feb 01 '18 at 14:50
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    Is this some kind of elaborately layered pun? Charlie -> C -> "C" is pronounced Si (spanish for yes) -> yes – BlackThorn Feb 01 '18 at 18:51
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    @BlackThorn: Yes, mnemonic, also No-vember. I'm a little unsure whether "I require medical assistance" being Whisky is a joke or based on reality :-) – mins Feb 01 '18 at 19:15
  • @WayneConrad: does "affirmative" mean "I understand", "I will comply" or what? – smci Feb 01 '18 at 21:21
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    @smci "Affirmative" is "yes" in response to a yes/no question. "Negative" is "no". – ChrisDevo Feb 01 '18 at 21:38
  • From the ICS ......CC I am (or vessel indicated is) in distress in lat… long… (or bearing… from place indicated, distance…) and require immediate assistance (Complements Table 2, Chapter 2, Section 10, Page 104 if required) How does this apply to ATC? – RoyC Feb 01 '18 at 22:14
  • @RoyC: The flag "C" means "Yes", and Charlie is equivalent to "flag C" in the mouth of the pilots who use this non standard terminology. – mins Feb 01 '18 at 22:18
  • Sorry you are referencing the ICS which has multi letter meanings and then you are telling us that that is not really what is being used and the pilot is saying Affirmative Affirmative? – RoyC Feb 01 '18 at 22:21
  • @RoyC: Affirmative. But if you want to chat, then let's go to the chat. – mins Feb 01 '18 at 22:22
  • FWIW, there are some competing theories on what CC really means, including this naval one. No one seems able to quote a source. – Pondlife Feb 01 '18 at 22:31
  • @RoyC: "From the ICS ......CC I am (or vessel indicated is) in distress in lat… long (...) Section 10, Page 104". You are looking at the Morse code part of the ICS. – mins Feb 01 '18 at 22:41
  • It could also be a the short for the aircraft registration.
    Twr: G-CD, report at point Papa
    G-ABCD: Charlie Delta
    I have no idea how formally correct it is but when using shortened registration for calls (obv it has to be initiated by the twr) and the info is not critical it is often heard.     – Caterpillaraoz Feb 02 '18 at 14:01
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CC is short for Click Click. In situations where a military operator was busy or where talking could prove fatal an incoming message would be acknowledged by a double click of the transmit switch on the radio producing a "click click" at the other end.

"CC" somehow got into informal usage rather than the more precise roger wilco or affirmative. In this context it would probably be used as an informal acknowledgement of a purely informational message.

RoyC
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To answer the OP's question, "CC" and/or "Charlie Charlie" mean absolutely nothing in air traffic control. In my 30+ years in ATC, I never heard, nor heard of, someone responding to a clearance with that verbiage. If I did, I would repeat the clearance because I had not received a valid read back.

RetiredATC
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2

Flying overseas in the 1970s we used "Charlie Charlie" (not CC) as affirmative mostly on HF (High Frequency) radios. UHF, VHF and FM radios were pretty clear and you could understand a word like affirmative.
But HF was often a weak signal; scratchy and full of static. Charlie Charlie (repeated like that) was better- easier to understand- than one word answers like affirmative. I was a young pilot then and I learned to use it from professional radio operators. I will defer to the other responder regarding it's historical origin.

HeavyIronDad
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"Charlie Charlie" was always "Confirmed Correct" in my understanding. If ATC asked a question like "Is that your final requested level" then "Charlie Charlie" was an acceptable and recognised informal reply.

Alan Lukes
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