Squawk 7701!
 

I was obtaining my departure clearance the other day (UK) and we were allocated a squawk code of 7701. I did not query it at all but I felt that it was a bit close to the emergency code in that in flight it is not beyond plausibility that the 1 switch could be moved accidently to 0 by fingers, a food tray or some other reason. Highly unlikely but a chance nevertheless. Surely out of the thousands of codes available, why give one so close to 7700?? If we had incorrectly set it and it had turned the radar screen red (?) and there had been lots of frantic calls here and there, would this sort of code continue to be in use for a standard flight? Also I have as I sure others have had 760* and 750* from departure clerance. Thank you for your replies.:ok:

V3

The problem is the LACK of codes available, Voodoo 3. Yes, there are thousands of codes available; 4096 to be exact. But either, more are needed, or someone could reinvent the transponder to use all 10 digits. By missing out 8 and 9, several thousand codes are NOT usable ( 5904 to be exact!). That is why squawks which are close to the emergency codes are in more frequent use.

I got the same code last year, I think I was in Spain. I thought it was a bit ominous! I didn't question it either, we got from A to B in one piece.

MK

Or we could use Mode S identity as well as SSR codes, 2011 in London FIR apparently.:ok:

Indeed, and then the fun begins trying to match flight plans to Mode S delivered callsigns that the pilots mistype into the FMS.:ugh:

If only when Mode A was invented they stuck a few more bits of data in....:}

Its wrse tan you think. Try leading and possibly trailing zero's added by the FMS, so it modifies whatever the pilot types - from the FPL! Then there are a number of a/c where the FMS inserts a blank after the three letter - yes a blank! :ugh: :ugh: :ugh:

So BAW224 = BAW 224 try matching that!

We regularly use 7601, 7701 etc. Just be careful! :)

Can someone from European/UK ATC advise us whether or not you want an aircraft in a rapid [unplanned] descent to squawk 7700?
Our training department is saying in Europe, ATC don't want us to change the assigned code in an emergency descent, it would "cause more problems" and you "can see we are in descent"
Thanks

From the pilot's perspective my take on this is that if you cannot get a word in on the RT (quite probable these days!) and you have to descend then squawk 7700. If you can put a Mayday out on RT then maintain the assigned squawk.

It's interesting that ***1 squawks are seen as potential problems, yet others which are also 1 digit away are not, e.g. 7570, 7610, and even 7000 - all of which are likewise 1 digit removed from a disaster squawk! Could it be that we see these as a difference of at least 10 numbers and they therefore don't register as close?

Think I'll make this the basis of my psychology thesis (if I ever study pshychology).

10 numbers different? If only we could use 8's and 9's in code allocation :}

BD

JustaFew,

For the benefit of the non-anoraks, the use of all 10 digits would have far reaching development implications as the whole code system was (is?) based on the octal base, ie 0-7. With a bit of luck someone will be looking to the future!

Sorry for the nerdy comment:8

I mean 10 numbers as in 7610 is 10 more than 7600 in 'normal' counting; 7000is 700 less than 7700 etc, but only one digit removed from the danger squawks due to the manner in which they are selected.

Interesting info everyone, thanks a lot. As Vintage ATCO says, I am always careful when setting squawks however on those occasions with a code so close to an emergency one, I must say that I did check that the correct code was set a number of times before we set off!! :)

"Can someone from European/UK ATC advise us whether or not you want an aircraft in a rapid [unplanned] descent to squawk 7700?
Our training department is saying in Europe, ATC don't want us to change the assigned code in an emergency descent, it would "cause more problems" and you "can see we are in descent"
Thanks"

European airspace is increasingly being divided vertically, often between different agencies. Squawking 7700 will alert all the underlying sectors and burn through any filtering in place. Squawking 7700 will also facilitate co-ordination between sectors and units as the emergency A/C is easily identifiable.

The perception that it may cause more problems came from the tendency of older processers to drop the callsign of the emergency aircraft. London FIR Area Radar units will not lose the A/Cs identity if an emergency code is selected. I cannot vouch for the rest of Europe but as most of Western Europe has newer kit than us I cannot imagine they would suffer the loss of callsign either.

Thanks Arkady - thats really useful info which needs to be published to all.

As Arkady has alluded to, by squawking 7700 it tells us that you have a problem. That, coupled with us seeing you in a rapid descent, enables us to get other a/c out of your way PDQ :ok:

From 4444:

8.8.1 Emergencies

8.8.1.1 In the event of an aircraft in, or appearing to be

in, any form of emergency, every assistance shall be provided

by the radar controller, and the procedures prescribed herein

may be varied according to the situation.

8.8.1.2 The progress of an aircraft in emergency shall be

monitored and (whenever possible) plotted on the radar display

until the aircraft passes out of radar coverage, and position

information shall be provided to all air traffic services units

which may be able to give assistance to the aircraft. Radar

transfer to adjacent radar sectors shall also be effected when

appropriate.

Note.— If the pilot of an aircraft encountering a state of

emergency has previously been directed by ATC to operate the

transponder on a specific code, that code will normally be

maintained unless, in special circumstances, the pilot has

decided or has been advised otherwise. Where ATC has not

requested a code to be set, the pilot will set the transponder to

Mode A Code 7700