I am suprised that somebody, presented with radar tapes, is going to argue with the CAA. On what grounds?

Sometimes one does wonder though. The other day I was flying N of Brize and on the handover to Shawbury was instructed to turn left urgently to avoid busting Birmingham airspace. I was flying a dead straight track on the autopilot and had two GPSs telling me I was 2nm outside it, and immediately following this instruction (which I obeyed) I got the DME from Birmingham's ILS which together with a ruler on the 1:500k chart confirmed I was exactly where I thought I was! I can only guess that either Shawbury's radar is ~ 2nm out in azimuth at the 35nm distance in question, or they incorrectly determined my track at that moment and thought I was about to bust. If this had resulted in a bust action I would have asked for more than one radar tape.

On another occassion I was flying about 3nm outside Lyneham's zone and was told I was infringing. I turned as instructed, but (as above) this conflicted with GPS+DME so I telephoned their ATC afterwards. They told me they had about 30 microlights bust their zone the day before and were telling people they were busting even when they looked like they might be.

IO540, I don't know the specifics, but if your at 35nm range from Shawbury's radar, you blip size may well be quite large if various filters etc are not switched on. I would certainly expect an aircraft with reasonable radar cross-section to appear to be at least 2nm across in azimuth. Combine that with a radar map which, although accurate, still has 'line thickness', a keen, puppy controller and you may well find that he/she believes you are about to commit a mortal sin.
Can't comment on Lyneham, sounds like ATC supervisor bull**** to me.:=

2nm diameter blip at 35nm?? That would explain a few things.

For a start it means that a functioning GPS will be far more accurate than a radar. I recall Irv Lee doing an article for one of the UK flying rags a few years back, where they flew around somebody's CAS and got them to check the accuracy of their GPS. Seems a completely pointless exercise to me, if the radar resolution is that poor. A functioning GPS will be about 100x more accurate than a radar, around the edges of the average Class D zone and assuming the radar head in the middle of it.

I wonder how accurate the resulting radar tape would be. The one which the DGAC used to go after me showed me only a few hundred metres inside the TRA. Funnily enough I was under a squawk at the time, a sort of "FIS with radar" which has since become common in France for VFR traffic.

However, the SSR return will give a far more accurate fix. :O

And if it's a fully processed radar of the type we use at TC, doesn't matter how far you are from the radar, your primary (and secondary) return never changes in size.

IO540, what are your calculations for the 100 times more accurate bit? Just that our radars and their maps etc are used for quite close tolerances with regards separation and vectoring etc and so are scrutinised rather closely for accuracy.

I based that on the 2nm diameter blip.

Sure one can reduce the size in software to something impressive but does this yield real position accuracy? From a 2nm wide return it won't - other than by averaging many returns which one can't do (for position fixing purposes) with a moving target.

A decent IFR GPS will be accurate to well within say 10m, everywhere, virtually all the time.

I would hope the radar would be more reliable, if not more accurate, because one could continually check it by marking certain ground returns (whose location is accurately known) onto the screen and checking where they produce a blip. I wonder if this is done.

There are numerous fixed points on our radar maps (VORs, NDBs, reporting points, centrelines etc) that aircraft fly over and that would soon show up any inherent innacuracies if pilots were reporting over them and the radar was displaying them a significant distance away from them. It doesn't.

Some primary radars do use known fixed ground targets for calibration/set-up checks.

In the case of the two mile wide return on an unprocessed primary, you work using the centre of the return as being the position of the aircraft, not the whole two mile wide blip.

Don't knock Shawbury and the advice given by them. The ATCOs there are unfailingly helpful and pleasant to everyone, including those who require serveral attempts to get them to read back correctly - I've heard them often enough! They are GA friendly and more than willing to help keep you out of trouble. I would far rather take their advice that I might be about to infringe Birmingham's airspace and find myself a couple of miles further away than risk infringing it. I will ALWAYS talk to Shawbury but rarely to Birmingham, especially after my last attempt to do so, preferring to keep down below their airspace. Which could easily have meant you were eight miles inside, instead of two miles outside, Birmingham's zone. I'll take Shawbury's advice any day.

I think the m stood for metres not miles!

I've always found Shawbury to be very helpful. No complaints from me. Brum can be good, can be bad. Seems to depend who's on (That's not just from a GA perspective, but also an airline one)

:O Serves me right for getting annoyed about someone not willing to take the advice of those who really would be trying to help. Where would he have stood if the GPS had been having a seriously faulty day and he had ignored the advice from EGOS ending up inside Birminghham's airspace? It seems to me he wouldn't have had a leg to stand on as Shawbury would, most probably, have on tape the advice they had given.

Fortunately at my unit infringements are quite rare (mainly because most of our airspace is well above the normal operating levels of GA aircraft I suspect), however we do get them.

Our first step in the case of an infringement will always be to track down the culprit, using radar monitoring, by speaking to other agencies who might be in contact with the pilot, etc, etc.

Once we know who it is then we'll try and invite the pilot to call us to discuss the infringement. If the pilot doesn't call, then we'll submit a MOR, a CA939 (Alleged Breach of Legislation), and all relevant recordings to the CAA and let them deal with things. We'll also provide an assessment of the impact on civil operations and any safety issues which arose.

If the pilot does call, then we'll let him put his/her side of the story, whilst we'll explain how it was from our point of view. The idea here is that we share the experience and learn any lessons which can help prevent a reoccurrence.

If the pilot is receptive and we get the impression that they have genuinely taken away something which makes them realise the potential (and actual) effect of their actions, plus things which will make them better educated for future flights, then we'll still file the MOR but provide information that appropriate counselling has been given and as far as the unit is concerned, the matter can be closed. We'll also almost certainly forego the CA939 action since the alleged breach of legislation has been dealt with satisfactorily (in our minds) and a prosecution would serve no purpose other than a punishment. Please note that this would generally be for infringements which didn't directly affect safety or cause massive disruption. In those cases, the high profile of the infringement might tie our hands and the CAA will probably wish much more robust reporting and reaction (at least on their part).

If the pilot is non receptive or continues to give the impression they are oblivious to the seriousness of the issues, then our counselling is obviously not working and our only recourse is to take full reporting action and let the CAA deal with it.

At my unit, the majority of infringements are by military pilots, some foreign, but mostly UK air arms. The trainee pilots seem to be the most receptive when discussing the infringement, whilst the steely eyed trained killers seem to try and blame anyone but themselves ;)

In terms of radar accuracy I'd have to check our documentation, but for our en-route processed radar the accuracy figures are in the order of +/- 1 degree of azimuth and +/- 0.1NM range.

You can use the 1 in 60 rule to work out how far out you might be displayed on our radar from your actual position depending on your distance from the radar head. :ok:

Serves me right for getting annoyed about someone not willing to take the advice of those who really would be trying to help

I am curious at astonishing the leap of imagination it has taken to reach the above "conclusion" from my entirely neutral technical discussion of radar blip size / azimuth accuracy. Nobody was criticizing Shawbury, who are unfailingly polite and helpful.

1 degree means 0.5nm at 30nm, which is obviously close enough to detect a real CAS bust.

I would agree that a radar system will be more reliable than GPS (which is why I would take a radar vectored letdown over a GPS approach) but there is no doubt that GPS is far more accurate in the 99.xxx% that it is working.

With a decent moving map, either displaying the actual CAA chart (this is now possible) or used together with the printed chart, it's quite hard to bust airspace.

The only time to my knowledge I have busted UK airspace was a vertical bust, when flying, at about FL053, under a piece of FL055-base Class A and then transiting to below an adjacent piece of Class A with a 5500ft base. This type of "let's see how many pilots we can catch with this trick" airspace design seems peculiar to the UK. The QNH was significantly off 1013 and this resulted in a bust of about 500ft. I was accompanied by an ATPL instructor, who was watching a moving map of the actual CAA chart, and he didn't spot it either... it won't take long to work out where this was but it was a long time ago and the tapes will be long gone. It was in the middle of the night and no radar service was available to us.

Sorry IO540, I have no idea how I missed the bit where you said you did as they asked. I do tend to get rather defensive when it comes to Shawbury as I fly through there reasonably frequently and they have always been very helpful to me. I am always amazed at their patience and politeness with all who use their services. I recently had a problem with my transponder and having spoken to D&D on the ground before I set off back to my home airfield,(there was a lot of Military traffic around that day and I wanted to be visible to Shawbury) I called them only to find that not only was there a problem with the transponder but the radio decided to have a tantrum too and I couldn't hear anything (I was plenty high enough at 3,100' for the Clee Hills not to be a problem). We eventually managed to make contact - they had been able to hear me all the time, and they kept an eye on me until I was safely back on the ground. As soon as I was able I rang them to thank them.

DGAC prosecution
 

I am expecting a letter from DGAC re landing at Cannes (without a prearranged slot) during the film festival/Monaco Grand Prix restrictions.
We had filed an IFR flight plan from Perugia (Italy) to Cannes and had been handed over by controller after controller (with no mention of special procedures being in place) until after landing one of the Cannes ground crew advised us of our oversight - I thought the film festival had ended but Cannes was still awash with luvvies and the special procedures were still in place!
7000 Euros was the threatened fine!
IO540 I am pleased to hear that you were not prosecuted especially since you were under a squawk.
I'll be checking the NOTAMs more carefully in future.

SB

SB - let me into a little secret: very few IFR pilots ever look at notams. You check the weather, file the flight plan, and if the FP isn't refused then you are "good to go". That's how it's been done since IFR was invented and that's how most old hands still do it.

If they prosecuted everybody who filed an IFR FP, which was not refused (despite the fact that the ATC at the destination has it on their system within seconds of you getting the ACK) they would be nicking the majority of bizjet pilots.

IO540, you are probably right that "very few IFR pilots ever look at NOTAMs" - it is certainly easy to slip into the habit of expecting ATC to take care of you in CAS - and most of the time they do (bless'em!:D). Our IFR flightplan was not rejected and at no point was it suggested to us that special procedures were in place at Cannes - in fact in the most recent Loop the article concerning the "race" from Cambridge to Cannes suggested that no special procedures were in place at Cannes - oh yes they were!

Although it is no excuse I had no internet access on the morning of the flight (Stayed in a friend's farm on a hilltop in Umbria where GPRS was not possible) and NOTAMs were not offered to me by (the incredibly slow) Perugia flight planning - so we just made tracks into the airways system and Cannes lured us in.

Hopefully the CAA Captain with the 2mm wide fountain pen will be on hand to fight my corner if I need him.

SB

Sorry but if that's the case, then they are idiots Checking the NOTAMS should be as automatic as checking the weather.

I know they can be a pain to get, but at least get the departure and destination and diversion NOTAMS.

That way you aren't relying on anyone else to do your work for you. Why should a controller check whether you have a slot? It may just be a data input monkey rather than anyone qualified. How are they to know you haven't got a slot?

Sorry, but there are no real excuses on that one. Even the most junior PPL trainee should know to check NOTAMS.If their FI doesn't mention it (which of course they should) then even a cursory glance at an air law course book will tell you.

Sorry SB, but I can't see much of a defence really. As Traffic Police are so fond of saying "ignorance of the rules is no excuse, Sir"

I didn't suggest one should not check notams; for example an approach aid might be duff so no ILS, etc.

It's just the pre-internet culture to not check them, and great many "old" pilots still live in that age. I did my PPL in 2000 and never got any notams. But then the website only appeared c. 2003 and barely worked even then. Now it's pretty good.

Mid August 2002. :ouch: ;)