Multiplex [Noun, -]: a difficult, unpleasant, or embarrassing situation.

Hello dear friends,

Has it ever happened to you that somebody you didn’t know called you on the phone by mistake? Technical problem at the switchboard, finger error when dialling, the mishap is reasonably frequent, sometimes funny or ironic, but one thing is certain, it makes us all realize how fragile communications are.

Of course, in a selective system like the telephone, i.e. where the initiator of the call actively routes his call to the intended recipient, the addressing part of the communication is relatively simple.

But what happens when, like in a half-duplex system, all messages are transmitted through a single, common channel, and it is only by a set of mutually understood rules and habits that one can recognize themselves as the intended recipient?

What if you could hear the telephone conversation of everybody in your street, and only by listening carefully to the contents of the messages, you could sort what is intended for you from what is not?

Quite a job, isn’t it?

Yes. And for it to work efficiently, the ONE quality that is required from ALL users is DISCIPLINE. I feel like (and you are probably mumbling at your screen) I am a 250-year old stern-voiced teacher talking to an audience of qualified individuals that of course know it.

And yet…

Here’s quite a piece of situation. It made people cry with laughter.

Saturday afternoon. CAVOK. All the airplanes are out flying. Controlled aerodrome (class D), and as you can imagine the controller is quite busy, but not so busy as to be overwhelmed. At the moment, he is on the phone with his colleague from an adjacent sector, so has no time to reply to the radio immediately. And the first pilot calls:

Student pilot: “OOABC for short circuit?”

The controller is busy and does not reply immediately. But someone else hears the call and replies. Somebody who feels very concerned, of course. Someone who badly wants to respond that Oh yes, by all means, he is able to perform a short circuit. Because that’s his aircraft. He is the instructor sitting less than 60 cm to the right of the student who placed the first call…

Instructor: “OOABC, affirm”

Oh happiness! The student is overwhelmed with joy about his apparent good idea, because somebody, whom he assumes to be the Air Traffic Controller, has agreed to his request! As a well-trained future pilot, he dutifully sends a read back:

Student pilot: “OOABC, roger, short circuit”

Instructor: “OOABC, short circuit.”

Then, of course it is a little bit weird, the student did not really expect another call from ATC after his read-back, but the success of his interaction with “ATC” just tells him to be happy about it.

Back in the Tower, our friend the Air Traffic Controller is sipping soda quietly, listening to the conversation unfolding, half puzzled, half amused. And then says out loud to his colleagues who witnessed the interesting situation from a distance: “So, what am I good for, if they do it all by themselves, now? Shall we call it a day?”, to the great amusement of all his colleagues.

Of course, it sounds extremely funny, and depending on your oratory talent, it is a funny mishap that will never get old. Absolutely true. Even putting it down in writing made me giggle, to be honest. 🙂

But then, what if it happens under other circumstances, that there is conflicting traffic or that ATC doesn’t realize what is going on for being too busy on something else?

What could have been done to prevent this from happening? (and deprive us of a good laugh, but let us be stuck-up for a little while)

Let us rewrite the conversation in a correct phraseology:

Student Pilot: “Tower, OOABC request short circuit”

And that is the end of it. The structure of the message alone will have told our instructor that the message did NOT come from the tower, but from somebody else in his very aircraft. Just his luck that this narrows it down pretty much to one other source! He would then (hopefully) have understood that ATC didn’t have time to reply immediately, and would have discussed with his student how to proceed next.

So, what we can learn from this happy episode, is to try and stick to standard phraseology all the time, or at least wherever standard phraseology lets us express ourselves accurately and completely. Save time, no need for repeats, better situational awareness for everybody, including, for example, if a foreign pilot is listening and is not accustomed to the idiomatic language of the country (s)he is visiting!

I know there are ways to sound cooler, like you are a controller at JFK during a peak hour, or as a 747-captain landing in Hong-Kong, but believe me when I tell you that standard phraseology is the way to sound professional. Your safety, our safety depends on professionalism, nothing else.

Thank you for stopping by, and until next time, then!