Jhooper From United States of America, joined Dec 2001, 6206 posts, RR: 11 Posted (12 years 6 months 2 weeks 4 days 12 hours ago) and read 4831 times:
Is there a system that ATC uses to assign transponder codes, or is it pretty much random? I've noticed that if I'm flying VFR into class D airspace, sometimes I'll get a code like 0432 (usually starts with a zero), whereas if I'm IFR I'll get a code like 4331 (usually starts with a 4).
Last year 1,944 New Yorkers saw something and said something.
To list a few highlights (remember each digit is only a three-bit Binary Coded Decimal, so its range is 0-7):
1200 is VFR traffic
2100-2500 for flights in Class A airspace (only 197 discrete codes at any given time?)
4000 series are flights requiring frequent course/altitude changes (test flights)
4400 series is reserved for pressure suit flights
Anyone know what the "FAKER" flights mentioned in 5-2-11 are? Sounds like one of those words you'd learn about in bad times ... like "SCATANA"
OE-LDA From , joined Dec 1969, posts, RR:
Reply 8, posted (12 years 6 months 2 weeks 2 hours ago) and read 4531 times:
As far as I know it is so that every ATC station has a set of transponder codes (e.g. Wien Tower (LOWW) has 0001 - 0012 or 0016, I am not sure) which they assign one after the other. But if you are handed over, let's say on a VFR flight from Wien Tower to Wien Information, you will receive a new transponder code, otherwise Wien Tower will run out of codes. Some airports have fixed codes (like LOAV departure is 1521). Then there are the general codes: 7000 for VFR, 7500 for hijack, 7600 for radio failure, 7700 for emergency.
ZID From United States of America, joined Jan 2002, 294 posts, RR: 4
Reply 9, posted (12 years 6 months 1 week 5 days 16 hours ago) and read 4444 times:
Each facility has it's own set of codes assigned for it's use. I can't remember exactly what the code range is for a flight that originates with Indy Center, but it includes the 6600's. At least twice a day I have to get a new code for a departure because the computer assigned a 666 code, and I just don't like issuing those codes.
Contact_tower From Norway, joined Sep 2001, 536 posts, RR: 1
Reply 10, posted (12 years 6 months 1 week 5 days 15 hours ago) and read 4452 times:
It is not a sipmple aswer to this question:
Most towers have a small "bank" of codes available for use in their airspace, or in a area not to far away. Additionally each Approach or Area Centre have a bank for flights in their area, if the area is large, some codes may not be permittet used in certain areas.
IFR flights generally keep their code trough out their flight, and it's picked from the Area code bank, but it the flight is long, a change of code might be in order. (Ex: the plane get a new code when crossing a certain FIR border or whatever)
The use of the code "banks" are a bit different from place to place.
Certain parts of the allotted bank might be for the specific FIR only, while another part of the bank is permitted used outside the FIR.
If I have a flight that depart my airfield for a short IFR or VFR flight to one of 4 neighbouring airports I can assign a squawk from our local bank.
If I have a flight departing to ENGM, wich is outside the scope of our codebank, I get a squawk from the Bodo Controll Centre.
They pick a squawk from a "outside FIR, inside country" code bank.
If the flight has ESSA as destination (not in FIR or country), they pic a code from a different bank.
That said, the code bank might be in a computersystem, or just a list on a pice of paper.
Our system will get a upgrade this spring, and ALL squawks for Norway will be assigned from a automatic central code bank, picking codes according to flight plan route.