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Does anyone know why we use Affirm and Negative in RT, rather than Yes and No? I assume it's to prevent confusion with accents and other languages - but Yes and No sound very different to me!

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Welcome to Aviation.SE and with a good, original on topic first question! – Simon Mar 1 at 20:54
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One wants to avoid getting "fsssssss...crk..." as an answer instead of "yes" or "no". It is much preferrable to get "fsssss.... ative crk..." instead. Which is also the reason why seemingly "silly" words like alpha, tango, or mayday are used. You don't want two things with different meanings that have an identical suffix or sound the same, and then being unable to tell which one it is. Such as: "Roger, krrrrrrrk.... ative". :-) – Damon Mar 2 at 12:37
    
Thanks for all of the great answers! I didn't think anybody else would be interested :) – CharlieEGMC Mar 5 at 12:45
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To further @damon's comment, here is a video of an agent in the field demonstrating why one should use the phonetic alphabet. – BruceWayne Mar 6 at 16:33
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Welcome! One question, one gold badge. Just go on! – mins Mar 6 at 18:18
up vote 51 down vote accepted

Because it makes you sound cool and very Top Gun!

Negative Ghostrider. The pattern is full

Seriously though, short words, especially at the end and beginning of transmissions are often clipped. When everything is busy, a question might only need a "yes/no" reply. Yes/no is easily lost in radio communication. Affirm/negative are not.

Also, with English native speakers, yes and no are absolute. In some languages, yes and no are relative to the question.

Interpret this:

Don't you have enough fuel to make the field?

Yes, we don't.

or

No, we don't.

Of course, the question is not good as it contains a negative but, if a question can only have an "affirmative or negative" response, it also helps the questioner to form a good question:

Can you make the field?

This can only be "affirmative (always shortened to "affirm" to avoid confusion) or "negative". There is no interpretation.

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I don't understand the point of your "Don't you have enough fuel to make the field?" example. As you say, it's a bad question to ask since it can't sensibly be answered with either yes or no, regardless of what words you use to communicate the ideas of "yes" and "no". – David Richerby Mar 2 at 0:28
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+1 for working a Top Gun reference into your answer. – Scooter Mar 2 at 1:48
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@Scooter ...and they should so have had "Scooter" as a call sign. – Simon Mar 2 at 8:04
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French still has three words: si is for a positive response to a negative question. Middle English had four words. The Celtic languages have no words at all for yes & no: instead, you respond with a form of the verb. So yes, it's complex. – TRiG Mar 2 at 10:23
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Perhaps as an example: You can't make it to the field? (Or ANY negative question, really.) With, for example, a German background this IS tricky, because German would allow both no for "no, you are wrong, we CAN make it" and "No, we indeed can't make it". Not sure how conventions for this work for a native English speaker. – Layna Mar 2 at 13:59

Why do we say "TANGO" on the radio for the letter "T"? Because "T" could get garbled or misunderstood to be "B", "E", "or "V". "NO" could become "oh?", "YES" could become "us", and so on...the possible interpretations and permutations of short, monosyllabic words are many. Use a big word and it will be hard to confuse with others...

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That's a very good comparison. +1 – mins Mar 2 at 8:52
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From an information-theory standpoint, the extra syllables (such as "niner" vs. "nine" that can sound a lot like "five" over a noisy connection) are "parity". They do not add any information, but provide confirmation that the information has been received correctly. The TCP packet used to upload this comment to SE includes a checksum that fulfills a similar purpose. The web server's networking stack re-calculates the checksum and confirms it matches. – Monty Harder Mar 2 at 16:38
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The term isn't so much "Parity" as "hamming distance" - the point is to ensure that there's always enough 'distance' between each transmitted symbol, that you can always detect a transmission error. That's why you get 'papa', 'charlie' instead of 'pee' 'cee'. – Sobrique Mar 2 at 20:43
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@MontyHarder There is also the zero-hamming distance of "nine" to German "Nein" (no) that should be avoided in an international context. – Chieron Mar 3 at 10:48
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The 9 vs nein is an important one. Similarly 9 and "no" in English are still quite similar, as is "mine". – Jon Story Mar 3 at 14:56

"Affirmative" and "Negative" come from the radio procedure words that went into the aviation world. As a comment above it also adds on more complexity and length to the statement so that the receiver can understand even if the transmission got garbled up or cut off in some parts. It would be really bad if the "yes" or "no" got cut off somehow from the transmission which would be really easy because they take a really short time to say, making it easy to loose the entire word over radio.

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Man years ago, I worked with computers and co-workers that had heavy accents. Our test machines were named 'svlnat01' and 'svlndt02' from the sysadmins which could be hard to differentiate from 'svlnap01' and 'svlndp02' style names. The names we assigned to the test machines were "Trinidad" and "Tobago" ('T' for 'Test') and production machines were "Nevis" and "Nassau" ('N' for first letter of site name on prod). Each syllable reinforced what you where hearing on the previous one rather than listening for particular ones amidst noise of formality and chance of misunderstanding over the phone. – user2896 Mar 2 at 19:58
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I have this argument over server names at almost every job I go to. After someone accidentally shuts down the wrong server because of this, they start to pay attention. – Sobrique Mar 2 at 20:45
    
The use of the word "Affirmative" instead of "Affirm" seems to defeat the purpose you describe. Go guess what "crk...crk.. ative!" means. – Dmitry Grigoryev Mar 4 at 11:24
    
@DmitryGrigoryev As opposed to just "crk...crk.." if they said "Affirm"? – immibis Mar 7 at 5:14

It has to do with how radios in general work or worked. This is also true with telephones and some VOIP situations.

So take a plain old radio. You set it to a frequency, then you push a button to talk. When you push the button a circuit completes that lets electricity flow through some components (used to be the mic, but now it's gone through changes at times, but it doesn't matter). Next the sound of your voice is encoded and applied over a carrier signal. Because that carrier signal can't be sent 100% of the time there was/is a bit of distortion at the start and end. In some radios they use a beep or click to help "establish" the carrier signal. Remember that the simplest radios just applied your voices wave form over that of the carrier signals.

Now, on the the receiving end, the same thing happens in reverse. The receiver can actually listen to the carrier signal the entire time, but there is a tiny delay as it starts to notice modulation of that signal, and starts "decoding it". Again remember the simple radio has your voice as a modulation of the carrier wave. These days there is a lot of logic on this end to filter out noise, but even if there wasn't it would still take a tiny amount of time to "see" that the carrier wave changed.

So you have several points of distortion and delay at the start and end of a message;

  • User pressing the button
  • The mic circuits "turning on"
  • The start of signal modulation
  • The start of signal demodulation
  • The Receiving end starting to "play back" the signal.

Add to that all kinds of distortion and interference, and the fact that as people we have a tendency to think along the lines of "push button -> talk" so fast that we often start "talking" before we are actually transmitting, and you can get some pretty messed up messages.

To combat that there are a few common things that are done.

  • Using longer words
  • Limiting vocabulary to common words
  • A set of hand shake phrases that ensure that both sides are getting the same thing.

For example (not from anything in particular):

You want pizza
ooo want pizza
ooo ..aunt... pee..ah

While a bit odd all three could be understood if your having a conversation about dinner.

Yes
ess
sss
ye..

Is harder to understand then

Affirm
..Firm.
Affir..
Ah.ff.

Specially when you are asking a yes or no question.

No
oh
n...
... (this is actually pretty common as yes and no are fast words to say)

So if you say into you radio "Do you want Pizza" and you get back: "...", your SOL. If you get back "oh", is that "oh I don't know" or the end of no? If you get back "Neg.." or "N....itive" or "Negiti.." Your still in good shape ( you have your answer).

There are many things radio operators are taught to do to make sure they can understand one another in less then perfect conditions. Using "longer" words is one, using distinct words is another, and using scripted responses and questions is a third. It's also important to remember that rarely is the radio a "primary job" it's almost always a "secondary job". The pilot needs to communicate, but communication can't be so cumbersome that it gets in the way of actually flying. So what ever system is in place to cover the distortion and what-not has to be easy, and widely understood.

Last example:

If you had two people with training, and they were taught that the question: "Do you want pizza?" could only EVER be answered with "... Yes ..." or "... No ..." then you could use yes or no, they sound different. But that means that the operator answering would have to press the button, count in their head to three, say YES, then count in their head to three, finally releasing the button. However if that operator was distracted, and didn't wait, or if the operator was out sick and the new guy didn't know the protocol, or there was a large network of people asking the question all with slightly different protocols, now "...Yes..." doesn't work as well.

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What if you get "...itive"? – Dan Henderson Mar 2 at 23:22
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That's why a lot of systems use something other then Affirmative. Like just Affirm or 10-4 or Roger or such. Different systems different rules, but that's the basic problem that is trying to be addressed. – coteyr Mar 3 at 1:03
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This good answer would be better if it used the actual "Affirm" from the question rather than "Affirmative", which is not recommended. – GreenAsJade Mar 3 at 3:29

Because it increases the number of syllables being spoken thus increasing the likelihood of correct communication.

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