Why A New Sqwauk Code

[WTF]

What is with the .....N472CF new x-ponder code 2645.

Why?

I have heard everything from controller preference, to get all on the "same page" to requirements for that sector.

What is the real deal?

Seems certain centers do it more often than others, and seems it has even trickled to approach and towers. ?????

 

[Seadogrun]

I always thought that the sqwak was assigned to another aircraft also causing one to have to change. At least that's what a controller told me when I asked him that. I'll be looking to see what the real answer is here.

 

[JCJ]

Some TRACON's have blocks of codes assigned to them (example -- LIT has 02XX) - if you depart LIT TRACON airspace (and don't already have an IFR squawk) you will need to either go to 1200 or go to a squawk available to ZME (usually a 55XX).

Most facilities have interfacility letters of agreement that address these things, and they'll be happy to discuss with you if you go visit.

Changing because another aircraft already has your squawk makes sense especially if you are on a long flight that covers several ATC sectors.

 

[glasspilot]

On international tirps when you go from on FIR to another it is very common to get another code. My impression was that the squak codes are only unique within a specific FIR.

 

[WTF]

Still confused

I was told by an ATC at an uncontrolled airport where they were there on the ground for a special assignment due to a golf tournament, codes are spit out and no 2 planes will have the same code...ever.

I know tracons have certain blocks of codes, but why the inconsistency. I have gone 10 legs from east to west north to south and never have to switch and then hop in for a trip from PBI to TEB the next week and switch 3 times.

 

[moso23]

it has to do with the automation between enroute facilities. i can only tell you about enroute centers as that's all i know. not sure how it works with terminal facilities as they use ARTS.

it often occurs when you've vacated one centers airspace (ie ZDC) and entered another centers airspace (ie ZNY). the reason why the computer at ZNY shows you on an 'incorrect' code is because the ZNY computer has another a/c in its system already on the code that you were on in ZDC's airspace. thus, the controller asks you to squawk a new code.

again, it has to do with the automation between HOST facilities. it has nothing to do with controller preference nor getting anybody on the 'same page'. if the computer advises the controller that you're on the 'wrong' code, atc has you squawk the 'correct' code.

hopefully i've cleared it up a little bit.

 

[Rizzo]

Sometimes if you come over on a "bad" code, and it's not being used by anyone else, we'll just assign your current code to you in the computer instead of having you change your code.

 

[WTF]

Thanks

Yeah that makes it clear. Appreciate it.

 

[Mooneymite]

They need to see you change your code, so they can verify the target prior to shooting you out of the sky.

No need to worry. It's all completely legal.