Squawk change

bimmerphile

SuperCritical™ Member
#1
What's the reasoning behind squawk code changes in flight? I can't find a consistent pattern of where and why it happens. Is it just so your previous one (assigned on the ground) enroute can be reassigned for another departure at your origination?
 

NovemberEcho

Dergs favorite member
#2
What's the reasoning behind squawk code changes in flight? I can't find a consistent pattern of where and why it happens. Is it just so your previous one (assigned on the ground) enroute can be reassigned for another departure at your origination?
Always wondered the exact reason but I'm guessing here it has something to do with us being fed from 3 different centers. It's really annoying, since the new code just keeps flashing at us and we can't do anything with your tag (hand offs etc) until you're squawking the right code.
 

JetBlast

Well-Known Member
#3
Center wise, when your flight plan gets transferred between centers, the computer checks to see if your code is already in use in that centers database of flight plans. If it is already in use, the computer assigns you a new one, if it's not, you get to keep the one you're on. The idea is to have as few changes as possible and let you keep the same code from gate to gate but unfortunately that's not always the case.
 
#4
Always wondered the exact reason but I'm guessing here it has something to do with us being fed from 3 different centers. It's really annoying, since the new code just keeps flashing at us and we can't do anything with your tag (hand offs etc) until you're squawking the right code.
I'm not sure if it's more or less comforting that you don't really know either.
 

NovemberEcho

Dergs favorite member
#5
I'm not sure if it's more or less comforting that you don't really know either.
There's lots of different reasons for a in-flight squawk change. I happen to know the exact circumstances bimmer is talking about though and although I had heard it had to do with squawk databases in various centers as jetblast said I didn't know for sure so just pleaded ignorance.
 

MarkZ

Well-Known Member
#6
@JetBlast is right. Each ARTCC has its own computer and beacon codes it tracks. When a new flight gets acquired by the radar and computer, the computer (ERAM) determines if the beacon code is already in use. If the aircraft's beacon code is already used, the computer will issue a new code. If an approach control is bordered by more than one ARTCC, the ARTCC that delegates that airspace to the approach control is the computer used to figure out beacon code conflicts.


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bimmerphile

SuperCritical™ Member
#7
@JetBlast is right. Each ARTCC has its own computer and beacon codes it tracks. When a new flight gets acquired by the radar and computer, the computer (ERAM) determines if the beacon code is already in use. If the aircraft's beacon code is already used, the computer will issue a new code. If an approach control is bordered by more than one ARTCC, the ARTCC that delegates that airspace to the approach control is the computer used to figure out beacon code conflicts.


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So if I'm arriving into EWR, and I get a squawk change from NY tracon, the ZNY computer makes that decision based on traffic in the whole center's airspace?

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JetBlast

Well-Known Member
#8
So if I'm arriving into EWR, and I get a squawk change from NY tracon, the ZNY computer makes that decision based on traffic in the whole center's airspace?

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It depends on which center the airspace "belongs" to. For example, one of the sectors I work serves three approach controls, BNA, HSV and CHA. HSV and BNA are all contained within ZME airspace so if you come from ZTL or ZID and your beacon code is already in use within ZME you get assigned a new code. CHA approach sits under ZME and ZTL airspace, but it's delegated to ZTLs computer so when an aircraft is handed off from ZME to CHA approach and that code is already in use anywhere within ZTL you'll get a new code.
 

MarkZ

Well-Known Member
#9
It depends on which center the airspace "belongs" to. For example, one of the sectors I work serves three approach controls, BNA, HSV and CHA. HSV and BNA are all contained within ZME airspace so if you come from ZTL or ZID and your beacon code is already in use within ZME you get assigned a new code. CHA approach sits under ZME and ZTL airspace, but it's delegated to ZTLs computer so when an aircraft is handed off from ZME to CHA approach and that code is already in use anywhere within ZTL you'll get a new code.
Precisely. I know there is a way for pilots to tell which approach control resides in which ARTCC. How one comes up with that information escapes me.


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bimmerphile

SuperCritical™ Member
#11
Cool, thanks everyone

Precisely. I know there is a way for pilots to tell which approach control resides in which ARTCC. How one comes up with that information escapes me.
I think it's in the Airport Facility Directory, each individual airport page identifies the controlling center. There's also a map of the centers in there somewhere iirc
 

BWER

Well-Known Member
#13
Or you could look at the center boundaries that are depicted on a high enroute IFR chart.

Not always the case. There are a few instances where a terminal hosted by another facility and it is not easy to see on a map who hosts it.

CKB is one example where Cleveland hosts it but underlies Leesburg (Washington) and Indy. At night when the approach closes each center takes their portion of the airspace.

Automation can get quiet complicated when you start looking at approach controls near center boundaries.

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PositionAndHold

Well-Known Member
#14
Every time crossing the Mexican border from the south headed to KSDM. As soon as we check onto Tijuana Appch and before SoCal, we get a change. Doesn't matter if we originated in Cabo or Panama. Every single time. I'm guessing it's a border protocol thing but have never been told why.
 

thesoonerkid

Well-Known Member
#15
Also each approach control has some subset of the overlying centers codes delegated to them for local use. These aren’t tied to the host computer.

So for example if a vfr guy calls up and after making sure he’s in my airspace as opposed to another sector I’ll him a code real fast (all I need is the call sign). This way I can radar ID him then figure out (as I have time) if he’s just going to land locally or wants flight following somewhere outside our airspace. If he’s landing outside our airspace then he would need a new code so i don’t have to do a manual handy with the center
 
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