Transponder Codes

[neilbradley1 2]

J.D.I have just completed an IFR flight from YPAD to YMML, a distance of 350 miles. During this trip I was assigned four different transponder codes.In Australia that just does not happen. There are only two enrote centres in Australia, Melbourne and Brisbane. Each centre has been given its own block of codes and they are allocated on a flight by flight basis and for the whole flight. New codes are NOT assigned crossing sector boundaries within both the Melbourne and Brisbane FIR's.Regards,NeilYPAD

[Ray Proudfoot 8,930]

Hi Neil,Four! :-eek I've never had four changes of transponder and that includes trans-Atlantic hops.It's changed on a random basis and I'm sure JD will say what the criteria is but my guess is that if you flew that route again you'd get a different number.Cheers,

[jd 57]

i don't want to get into an if statement for every country, to determine transponder code changes. i'll ask my uk controller, and see if it would be safe to say, transponder changes are rare for non faa flights, then i can probably make that change in v5jd

[neilbradley1 2]

Ray,Yes I was gob-smacked also. However as one who was on the inside with the development of The Australian Automated Air Traffic System (TAAATS), there was great concern expressed by all parties, ATC and Airlines, that there be only one code per flight issued. And that's what they got.Also while I am on it, I think the sector map for Australia is out of whack. Again too many frequency changes. If you like I could obtain the current sector map for you, if it would help?Neil

[jd 57]

i pulled the sectors out of fs2004. we'll probably be revisiting boundaries world wide in v5jd

[Guest hlm65]

I did many many flights with RC4 and usually I don't get many transponder code changes. One that should surely happen should be at least when entering Canadian airspace from Europe and vice-versa, I think.

[neilbradley1 2]

Not necessarily. If Canada has a SSR code allocation agreement with the Europeans (as Australia does with SE Asia) then the code allocated with the Airways clearance may hold all the way.NeilYPAD

[Ray Proudfoot 8,930]

Hi Neil,Yes, my gob has also been smacked on some occasions :-lolI hope you don't think I was ignoring you. Far from it but JD, as the programmer, was in a position to answer whereas I, as the humble voice processor, couldn't really answer on his behalf :-hahCheers,

[PeteP 2]

Neil,I'm afraid it's not as straightforward in Europe as you seem to suggest it is in Australia. We do have an international code allocation agreement - ORCAM - but with the amount of aircraft in the air over the busier parts of Europe and the limited number of codes available for worldwide transit use - theoretically 4,096 but with large blocks reserved for military, local and special purpose uses, in reality considerably less - it's inevitable that a large number of long distance flights, to, from or overflying Europe will get at least one transponder code change.Some long-distance flights will be unaffected but, equally, some short-distance flights will get a change because of the juxtaposition of multiple ORCAM regions they may pass through. Some centres such as Maastricht UAC, for example, sit on the boundary of several ORCAM regions and all flights entering Maastricht airspace from the north require a code change to avoid conflicting with the codes worn by aircraft entering their airspace from other regions. This is a fairly common situation here.As jd has pointed out, he doesn't want an "if" statement in his code for each country so, with RC outside the US, we try to steer a middle course with things like this which gives a reasonably accurate feel to non-US ATC procedures without claiming to be 100% accurate for any particular country. Maybe one day there will be country or region-specific versions but at the moment we have to keep things generic.I agree that 4 code changes is unrealistic for any flight let alone a short internal one. So, for version 5, I've suggested to jd that he continues with the occasional random code changes with a maximum of 2 for any single flight which will take place only at national boundaries rather at sector or same-country FIR/UIR boundaries. This should prevent any occurrences on internal flights such as the ones you got but will still allow a "flavour" of changes because of the type of conflicting ORCAM region codes I mentioned above.Pete

[neilbradley1 2]

Pete,I have the highest regard for JD and his team. My work on TAAATS Project gave me an insight into the complexities of programing, so I do understand the problem, and the bigger it gets the bigger it gets.Australia while its two FIR's cover about 1/9 of the worlds surface (but only about 3% of that has radar coverage), compared to Europe and North America, relatively we have very few aircraft in the air at any one time, so the 4096 codes, even with the military blocks taken out, go a long way.Anyway, on reflection although I have flown that rout a number of times, this was the first time this has occurred. Maybe I hit the random, random, random code line.Please take my observations as constructive points of view.NeilYPAD

[PeteP 2]

Please take my observations as constructive points of view.Of course, Neil and I hope neither I nor anyone else here gave you reason to think otherwise. We welcome input from all users and the team takes careful note of and frequently discusses the suggestions and comments posted here.As you mentioned you were ex-ATC I thought you might appreciate some background on why RC outside the US is set up the way it is. To be honest, I don't see the generic nature of the procedures and phraseology used for the non-Us parts getting any less so in the immediate future either. The more work I do on researching international ATC procedures, the more variations I find. Emulating US ATC is a relatively simple task - an integrated system with a single controlling authority setting the rules. In the rest of the world, everything is (usually) done on national boundaries despite the contribution from supranational organisations like Eurocontrol. For example, you have 2 centres for the whole of Australia, the US, I believe, has somewhere in the region of 21 and in Europe, we have 41 despite all 3 areas having similar-sized land-masses! Heaven alone knows how many more there are in the rest of the world but the vast majority seem to operate as individual units under the control of their own national administrations, each with its own set of variations from ICAO SARPS. Trying to find common phraseologies and procedures to use in RC is very difficult and at times it's completely impossible to answer a question from jd such as, "what's the Euro/ICAO equivalent to...". Usually, the only solution is some sort of compromise but, as with all compromises, someone will always be left feeling unhappy. :( Keep your comments coming.Pete

[neilbradley1 2]

Pete,I understand the problem. In Australia from 1945 when ATC more or less began here, because of our isolation and lack of contact with any significant adjacent ATC country, we were guilty of re-inventing the wheel in many areas. Australia had its own domestic DME right into the eighties, and CRUISE meant something entirely different to us than the rest of the world. It took a near miss over the pacific between two B747's to highlight the problem and force us to align with the rest of the world.ATC standardisation is a worthy goal, but in reality it tends to be subject to local interpretation, and also which major aviation nation had influence over the local area. Japan would have been greatly influenced the post war American occupation, and British colonies world wide by the way the UK does it etc.ATC operations manuals are as common as State AIPs which are all variations on generic ICAO Doc 4444. Thank you for your encouragement, I will keep on commenting as I would like to see a good product reach its full potential.NeilYPAD