It is done in software on the radar called Controlled Airspace Infringement Tool (CAIT) that alerts the controller the moment you cross the line.
btw, I had an argument once with ATC in the US who thought I’d crossed the line, but I had GNSS (this was a while back) and I clearly hadn’t….
Makes me wonder how accurate the Radar fix is. (probably better than 30m, but curious exactly what it is)
Timothy wrote:
It is done in software on the radar called Controlled Airspace Infringement Tool (CAIT) that alerts the controller the moment you cross the line.
OK. Does this mean it has to be “unknown” (squawking 7000) ? or does it also pick up non transponder aircraft? or does it filter out all squawks that not explicitly has been given a clearance? Also, is the system set up so each controller has his own “patch”, and what happens in between is a no mans land ? Is there any communication between controllers/software in nearby airspaces?
We have some discussion of CAIT here and a search will find it. I have never seen details published but it is fairly obvious how it works in general i.e.
In the UK, you are always assigned a unit-specific squawk before authorised entry into CAS, so anybody on say 7000 and showing 2600ft, in CAS whose base is 2500, must be a bust.
Radar is much less accurate than GPS. Some past discussion and ATCO input suggests +/- 0.5nm at 30nm. It works fine for separation of course because multiple targets will be similarly in error.
In the case of the CAA going after you over a bust, I am not familiar with actual cases but it sounds like you cannot submit any evidence in defence or mitigation unless you stick the middle finger up i.e. refuse to participate in whatever punishment has been assigned (e.g. refuse Gasco), appoint a lawyer, and present your GPS track in a court. It’s a high risk strategy because if you refuse the assigned “processing” your license is removed immediately. OTOH I hear it is fairly common for pilots whose license has been removed to appoint a lawyer…
2 years ago I contacted [the CAA man who threatened to sue if his name is mentioned] about the dodgy questions in the online exam and was told pretty forcefully there is nothing wrong with dodgy questions because if you got the “ok” ones right you would still get a pass mark. This leads me to think the process is totally one-sided.
Peter wrote:
if you refuse the assigned “processing” your license is removed immediately.
If it looks like a racket, sounds like a racket… it must have a royal lineage somewhere. :D
Peter wrote:
Radar is much less accurate than GPS. Some past discussion and ATCO input suggests +/- 0.5nm at 30nm. It works fine for separation of course because multiple targets will be similarly in error.
I wouldn’t bet on that. But it will work fine anyway because radar separation is several times larger than 0.5 nm.
Peter wrote:
In the case of the CAA going after you over a bust, I am not familiar with actual cases but it sounds like you cannot submit any evidence in defence or mitigation
Clearly you can because each month there are a small number of “action not taken, transponder found to be in error, no infringement occurred” cases.
Timothy wrote:
Controlled Airspace Infringement Tool (CAIT) that alerts the controller the moment you cross the line.
Or before you cross the line – a report a couple of years ago pointed out a problem that CAIT was flagging traffic it thought was likely to infringe but hadn’t yet done so (and that ended up not infringing at all) – it’s possible since then they’ve modified the code not to do this of course.
Clearly you can because each month there are a small number of “action not taken, transponder found to be in error, no infringement occurred” cases.
Yes; that is true.
What we don’t know is how much hassle the pilot had to go to. It is even possible he/she got a lawyer. The CAA is hardly going to have a category for “pilots who got let off after we got contacted by a lawyer” 
I have already been told by the [no name] CAA guy that some cases take months to resolve. He gave an example of an infringement in May, appearing in the May stats, which may not be resolved until July/August, adding “This can be even later should supplementary reports be required to establish the true facts.”
In the data it says e.g. “Transponder unserviceability confirmed by licenced engineer, no infringement occurred (2)”. How does this work? If the transponder was “unserviceable” then of course no infringement occurred 
Unless you busted a CTR/CTA but then this would be irrelevant; you have busted.
The only way I can see this working is e.g. you were picked up on radar 300ft in CAS but a subsequent transponder check found that it was reading >300ft too high.
Then you are open to getting busted for flying with an unairworthy aircraft. You might have some fun getting that radio check organised by the same firm which did the radio check a short time beforehand
It might work for a renter, who has little interest in what happens to the owner.
problem that CAIT was flagging traffic it thought was likely to infringe
which would not be much good anyway since in the vast majority of cases in the UK, you are not talking to the airspace owner, and in most Class A cases you cannot do so anyway (as VFR traffic). Sure you can call up Gatwick Director for a service but IME they are likely to send you back to London Info.
Peter wrote:
Then you are open to getting busted for flying with an unairworthy aircraft
Unlikely, because there is no way for the owner to know (if they have an old Mode-C transponder) that their transponder is giving the right response unless they are in two way contact with ATC, and the CAA knows it’s unreasonable to have a formal transponder test before every single flight.
I have first experience of this when my old Mode-C box reported me around 2000 feet higher than I actually was while leaving Barton (yes, it was during the current regime). There wasn’t even a followup afterwards, just a request to switch to Mode-A only. No attempt to “bust me” for unairworthiness or anything else. It was probably obvious to the Manchester controller that the Mode-C was false, because while my plane has a good climb rate, it’s not Saturn V. The fault was intermittent (and may have been a dropped bit, since Mode-C doesn’t have any kind of checksum) so subsequent transponder checks showed the right pressure altitude. That box is history now, though and the new one displays the pressure altitude at all times and Mode-S has a CRC so it’s much less likely that there will be a receive error.
(Acutally it’s not entirely history, it sits in my project room along with its encoder, on my list of projects is to build something with my LimeSDR to do transponder tests – although given its output power, constructing the filter is going to be an interesting challenge I’ll probably need some help with).
Peter wrote:
which would not be much good anyway since in the vast majority of cases in the UK, you are not talking to the airspace owner, and in most Class A cases you cannot do so anyway (as VFR traffic). Sure you can call up Gatwick Director for a service but IME they are likely to send you back to London Info.
That’s not true – you can use FMC, and there’s an applicable FMC pretty much everywhere now. As Timothy has reported, if you use the FMC and have Mode-S they will call you if it looks like you’re going to infringe. ATC doesn’t want the MOR paperwork any more than the pilot wants to go on the GASCo course. In fact on recent flights it’s pretty clear that both ATC and London/Scottish Info are actively trying to prevent infringements. Every flight I’ve done where I’ve been pointed towards CAS, the controller or London Info has always had me confirm that either I’m going to ask for a clearance, or remain outside of CAS. They didn’t used to do that as recently as last year.
