ATC IssuesA place where pilots may enter the 'lions den' that is Air Traffic Control in complete safety and find out the answers to all those obscure topics which you always wanted to know the answer to but were afraid to ask.
The idea is that areas that use the same codes should be far enough apart that there is little or no possibility of wrong radar identification
Now developing further into
CCAMS: Centralised SSR Code Allocation and Management System (in evaluation mode)
Aimed at improving safety, CCAMS assigns SSR codes to flights in the IFPS zone automatically and more efficiently than the current ORCAM rules. A more efficient use of SSR codes will prevent flight delays and increase safety (e.g. due to less code switches). CCAMS functions include: receiving and processing 4D flight data, assigning SSR codes to flights while preventing code conflicts, identifying crossed ATSUs and distributing them the allocated SSR codes. With the CFMU 12.2, the CFMU is ready to start operational evaluations with volunteer ANSPs.
For more details, consult the Releases Deployment Plan in the CFMU website’s Library.
Transponder codes are assigned in the UK by a section of the CAA in the Directorate of Airspace Policy (DAP). If they are not ORCAM codes, eg are assigned to individual airfields or ATSU's, DAP have to ensure they are not duplicated by with the assignment to neighbouring units in order to avoid the two units assigning the same code to different aircraft in the same area, for instance, the Farnborough 04XX allocation is also assigned to Lakenheath and Birmingham, all three being deemed to be far enough apart to avoid confusion.
Some areas of the world I fly in will leave my squawk when I change FIR's (example is UAE to OMAN) and other's will change it. And sometimes the change differs to, if that make sense (May be a 6*** or a 4***).
Would there be a reason for not changing the squawk on an aircraft coming into your sector as opposed to changing it ?
As you pass from one ORCAM region to another, for example from Copenhagen UIR into Hannover UIR (under control of Maastricht), you get a squawk change.
In this case you would be assigned a 07** or 34**code. The system will try to assign a code that allows you to change as few digits as possible within the constraints of the situation e.g. code not assigned in the past hour (or so).
If you then flew further into the Amsterdam and London UIRs which are in the same ORCAM region you would not have to change codes.
Hope this helps but feel free to ask more specifics if you like.
I find it quite interesting that my transponder code very rarely changes flying across S-E asia. Does the region have a similar code allocation scheme and are there enough codes for all of us?
Also on initial contact most ACCs want us to report the transponder code as a means of identification, again something I haven't seen in Europe or N. America. Any specific reasons why ident or a code change isn't used?
Edit to say I'm referring to Lumpur, Kinabalu/Kuching, Singapore, Jakarta, Ujung, Bali, Bangkok, Ho Chi Minh, Phnom Phen, Hong Kong, Manila, Taipei, Guangzhou ACCs.
Last edited by babotika; 7th Feb 2010 at 10:44.
Reason: Added detail
In Australia the Eurocat-X system assigns codes automatically when filed flight plans become "pre-active", 45 minutes before ETD. These are displayed to controllers in the Electronic Strips. Hence if you are flying into an Aussie FIR with a code you will be asked to change it.
The reason being that the code that was available in the previous FIR may not be available, that is it is already being used, in the receiving FIR. Everyone is striving for seamless transfers however the limited number of SSR codes makes that very difficult.
When we finally move to a world wide ADS-B system each aircraft can be identified by it's 24 bit ADS-B code so I think transponders may become obsolete.
I have done a bit of a trawl on the internet and although I couldn't find a map or list of states I am sure the ORCAM method, developed by Eurocontrol, is applied in the APAC (ICAO desigantion for Asia Pacific) area. I have found minutes of meetings where issues associated with it have been discussed with recomedations made. In some other areas of the world e.g. South and Central America they refer also to PAs (Participating Areas).
Have a look at the last page of the document in this link to see a good example.
Location: In some hotel downroute or in some hotel doing union negotiations.
The medium to long term aim in europe is to get rid of individual squawk codes for all IFR flights and use the Mode-S downlinked flight id (callsign) instead. That is currently under liive test at least in germany on certain domestic routes. All flights on that route get assigned the same quawk (2000 iirc) and the ATC system allocates individual information via the mode s flight id.
When i fly from Mumbai FIR to Oman FIR, Muscat CTR allocates a new code depending on destination. But on the way back, Mumbai FIR is happy with the code allocated by Oman / UAE FIR. Just wondering why is it so.
ORCAM and mode S work OK as long as the aircraft remains within controlled airspace. But as soon as it leaves it becomes just another conspicuity code as it does not indicate which ATC unit is providing the aircraft with a service. This is important where you have several units operating in the same airspace.
I think Toadpool is referring to the UK. In UK controlled airspace you can usually work out who is providing a service to an aircraft by it's position. Outside controlled airspace it's not so easy as an aircraft may be receiving a service from one of several local units, from one of several military units or not receiving a service at all. To cope with this the UK allocates blocks of Mode A codes to units which allows other controllers to identify who is controlling traffic which may affect their own aircraft. As Toadpool says this easy useful scheme won't work with Mode S and NATS and the Military are currently figuring out what to do instead.
I was indeed referring to UK class G airspace, where you can have several units controlling traffic in the same airspace. In this case an ATCO would need to be able to quickly identify which other unit is working conflicting traffic for co-ordination purposes.