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.
Can any one shed any more light on the reason why we were asked to squawk 1000 whilst speaking to Rhine Radar this afternoon whilst heading East? When asked to do so we looked at each other in puzzlement on the flight deck and asked for confirmation from ATC!
A little bit later the curiosity got the better of us and we asked for the reason why. ATC said that they use the Mode S readouts and that in order to do so, we needed to squawk 1000. Sounds a bit odd. Never had to do this when passing through the same sectors on previous trips. Also, didn't have to do so on the way back to the UK.
If you are Mode S equipped and the ground unit is able to validate your downlinked aircraft identification against that in your flight plan then the Mode A code isn't needed for identification and you can be given the Mode S conspicuity code which is 1000. Not many ground units can cope with that yet but it will start to become the norm over the next few years.
Just to add slightly more detail. The fact that you are now squawking A1000 means that an ATC unit, working with Mode S, has verified that your Mode S ID is consistent with your call-sign, be that registration or trip number.
Which, in turn, is of course part of a grand plan to mitigate the acute shortage of Mode A squawk codes across much of Europe.
It's also the reason why from time to itme you will see Maastricht instructing flights from the UK to change their Mode S callsign at the FIR boundary when they have either forgotten to use the correct alphanumeric or failed to set the outbound Flight ID on a turnround.
Until recently, Sq 1000 and Mode S identification was only used for flights operating entirely within airspace that could handle it, so between FRA/MUC/AMS/CDG and operating with Maastricht/Rhein/Reims/Paris/Amsterdam/Langen/Munich ACCs.
What has changed recently, is that Sq 1000 is now being issued to aircraft mid-flight that were previously correlated on a Mode A code. Once the Mode A code is no longer needed because all of the remaining units along the route of flights are Mode S equipped, then the Mode S can be used, Sq 1000 issued, and the Mode A code released for use again.
Maastricht are now using this procedure for aircraft that must have a squawk change anyway. So for example, aircraft coming in from Scandinavia, that is in a different code allocation PA, have to have their squawk changed coming southbound. This will now be 1000 for those going to suitable airports.
Flights that depart from within the Mode S area, but are leaving it, will be given a normal Mode A code from the start because otherwise they would have to have it changed as they approached the boundary with the non Mode S equipped ACCs.
At present, aircraft that are correlated using a Mode A code, but are not required to change, for example flights from the UK into Europe, are being left on that Mode A code, to prevent an increase in workload.
Eg. Flight ARN-FRA
- Mode A allocated on departure, for use by Sweden and Copenhagen
- Must have a squawk change on transfer from Copenhagen to Maastricht, remaining units are Mode S capable, so given Sq 1000.
Return flight FRA-ARN
- Must be on a discrete Mode A code on transfer from Maastricht to Copenhagen, so given a Mode A code from the start.
- Although on transfer from LACC to Maastricht, the remaining units are all Mode S capable, Sq 1000 could therefore be used, this flight stays within the same code allocation area, so no change is necessary, so it is left as it is on the original Mode A code.
Were you by any chance headed for Prague? If so, then I think a squawk change is needed when you go from Germany to the Czech Republic, which is why the 1000 was given by Rhein going eastbound.
Last edited by GlobalJourney; 7th May 2012 at 19:40.
Slight side note : Wrong mode S aircraft IDs can be bothersome to controllers as they add an extra line to the label of the track. (at least that's how it is at Brussels ACC, also mode S airspace btw) If the ID is not the same as the callsign of the flightplan the transmitted ID is displayed in green above the FPL callsign.
There is a difference between having Mode S data visible and the Centre system being able to use that data to correlate the flight plan and the radar track. UK controllers can see the Mode S data but the Mode A setting is what is used to associate the flight plan with the radar track and will be for some considerable time. You can't use the 1000 code if you still need the Mode A code to make that link.
The brussels ACC system correlates track and FPL using mode S as primary and, in case of no a/c ID or wrong a/c ID, it checks mode A. All units have mode S capability, even the towers. (even EBBR's ground radar can display the mode S aircraft ID).
We don't change the mode A to 1000 at this time. If you want the exact reason why I'll have to check with someone...
Location: The Peoples Alcoholic Republic of Jockistan
Yes we can, if we open up a Mode S Information box, but do nothing about incorrectly inputted IDs, because we are not using it to identify the aircraft. We use the correlation of the SSR Code and the data held in the Flight Data Processing, or the raw SSR code, to identify flights, for now.
UK ATC'er Old enough to know better, young enough to carry on regardless.