Zone Infringements - why ?
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GPS is GPS, who cares what it is certified for for VFR flying, its more accurate than anything else out there.
5nm error....never (without you knowing about it). I have used GPS since 1995 to position equipment for the oil industry and have never had more than a few second nav jump. Accuracy is now within metres even on my cheapo eTrex sub £100 unit. Try this with an NDB.....
dB errors....possibly. Thats why I would create GPS waypoint on the centre of the zone, and ensure my GPS DME never drops below 5 miles or whatever, or download "official" waypoints.
5nm error....never (without you knowing about it). I have used GPS since 1995 to position equipment for the oil industry and have never had more than a few second nav jump. Accuracy is now within metres even on my cheapo eTrex sub £100 unit. Try this with an NDB.....
dB errors....possibly. Thats why I would create GPS waypoint on the centre of the zone, and ensure my GPS DME never drops below 5 miles or whatever, or download "official" waypoints.
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RNP5, AIUI, refers to nav capability. It doesn't have any relationship to the actual equipment. Meeting RNP5 just means the device meets RNP5. It says nothing about the device itself, and most importantly, it does not imply that the device will only just meet it.
GPS is either working (and accurate to a few metres 99% of the time, and a few more the rest of the time) or it isn't (no reception, device has failed, etc).
I would bet that RNP5 goes back to inertial derived navigation, where an error of a mile or two is entirely plausible. INS uses DME/DME to keep itself reasonably accurate but often it won't have DME reception (e.g. over large swathes of France).
KNS80 and similar old RNAV solutions (VOR shifting) also comes to mind as likely applicable to this.
GPS is either working (and accurate to a few metres 99% of the time, and a few more the rest of the time) or it isn't (no reception, device has failed, etc).
I would bet that RNP5 goes back to inertial derived navigation, where an error of a mile or two is entirely plausible. INS uses DME/DME to keep itself reasonably accurate but often it won't have DME reception (e.g. over large swathes of France).
KNS80 and similar old RNAV solutions (VOR shifting) also comes to mind as likely applicable to this.
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The CAA recomend that pilots try to miss zone boundaries by 5nm laterally (the 5nm allowing for navigation errors).
even approved IFR panel mounted units are RNP5 - they only keep you within 5nm of track
Its up to the pilot to follow the route displayed.
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Flower,
Here is my interpretation of what seems to be happening in the GA environment.
Infringements happen because they are flying too close to zone boundaries, either deliberately or because they are lost. I would therefore summise that a proportion of infringements are pilots who are lost. Others will be those who are cutting the margins to the limits on their whiz bang nav sets who genuinely believe they are clear of the zone. Case 1 is a serious problem and needs addressing. Case 2 is less of an issue since the pilot knows where he/she is and acknowledges the existance of a zone, but is just the wrong side of the line by a small amount.
IO540
The King Air incident was repeatable and as you say GPS's are not inherently inaccurate, so the make and model of the set is largely academic. Therefore it must be the database that was incorrect. The question is which database? The database that the controller's radar uses to overlay the zone boundary or the GPS data base? It is the answer to that question that I would like the answer to.
Unfortunately I do not have a moving map GPS, but here is a challenge for someone who does. Take the SW corner of the London TMA where the King Air infringement happened. Find its lat and long in the AIP and load that position into the GPS as a way point. Then see where it is relevant to the moving map's location of the zone boundary. Perhaps that will answer my question.
Here's another thing. How many pilots check that their GPS set is using the same survey datum as the CAA charts? I am sure that those who know about it do, but does the average spam can hirer?
Here is my interpretation of what seems to be happening in the GA environment.
Infringements happen because they are flying too close to zone boundaries, either deliberately or because they are lost. I would therefore summise that a proportion of infringements are pilots who are lost. Others will be those who are cutting the margins to the limits on their whiz bang nav sets who genuinely believe they are clear of the zone. Case 1 is a serious problem and needs addressing. Case 2 is less of an issue since the pilot knows where he/she is and acknowledges the existance of a zone, but is just the wrong side of the line by a small amount.
IO540
The King Air incident was repeatable and as you say GPS's are not inherently inaccurate, so the make and model of the set is largely academic. Therefore it must be the database that was incorrect. The question is which database? The database that the controller's radar uses to overlay the zone boundary or the GPS data base? It is the answer to that question that I would like the answer to.
Unfortunately I do not have a moving map GPS, but here is a challenge for someone who does. Take the SW corner of the London TMA where the King Air infringement happened. Find its lat and long in the AIP and load that position into the GPS as a way point. Then see where it is relevant to the moving map's location of the zone boundary. Perhaps that will answer my question.
Here's another thing. How many pilots check that their GPS set is using the same survey datum as the CAA charts? I am sure that those who know about it do, but does the average spam can hirer?
I use GPS to tell me roughly where it thinks I am - and a CAA 1/2 mill chart to confirm that. I do not think that reliance on a basic GPS moving map will ever be safe unless the software is regularly corrected. None of my a/c GPS systems has a moving map and we do NOT update the waypoint database - this then forces pilots to use it as a back up to traditional VFR navigation on pre-planned tracks between specified points using the CDI scale with +/- 1.25 mile fsd sensitivity. The edge of a CTR may change, but lat/long never will!
But I wholeheartedly agree that it would be nice if a good ground feature could be used as a delineating feature whenever possible. Years ago I did low level local air defence in the F4; up to the stop line we would chase any hostiles, beyond that the Bloodhounds would take them out. It was dead easy (and quite wise) to knock off any attack before infringing the Bloodhound engagement zone as the boundary was well defined by the main A14 Ipswich-Stowmarket road.
But I wholeheartedly agree that it would be nice if a good ground feature could be used as a delineating feature whenever possible. Years ago I did low level local air defence in the F4; up to the stop line we would chase any hostiles, beyond that the Bloodhounds would take them out. It was dead easy (and quite wise) to knock off any attack before infringing the Bloodhound engagement zone as the boundary was well defined by the main A14 Ipswich-Stowmarket road.
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Beagle
If the RAF still navigates this way, it is as well it is the Americans who get to do the dirty (but usually necessary) work around the world today!
Recently I spoke to a Hawk pilot (an instructor as it happens, too). He said they navigate absolutely using dead reckoning, map, stopwatch. GPS is out of the question. I asked him what would be the function of a Hawk in a real conflict. A long pause followed........ the enemy would only need to wait for some clouds to form
Droopystop
The SW corner of the 2500ft+ TMA is, measured from the displayed map
Jepp Flitemap (current Jepp vector database)
N 50 58 31
W 000 34 28
Jepp Flitemap (current Jepp "VFR raster charts" database)
N 50 58 31
W 000 34 23
Navbox Pro (current Navbox database)
N 50 58 20
W 000 33 40
Memory Map (2004 CAA 1:500k chart)
N 50 58 29
W 000 34 25
Memory Map (2004 CAA 1:250k chart)
N 50 58 31
W 000 34 27
OziExplorer (real 2004 CAA 1:500k printed chart, scanned, my own map calibration)
N 50 58 32
W 000 34 23
All the above are within the thickness of a line on the printed chart.
Perhaps someone with more time will look up the official lat/long in the AIP but frankly I doubt ALL the above products are wrong! I also know the last one above was no more "wrong" than the printed CAA chart itself because one can overlay the chart grid onto the map display and see if the two grids line up.
So I wonder just what "database" the King Air was using.
How many more GPS navigation products do you want me to dig out? I have an old Skymap 2. I also have a KLN94 and KMD550. But these all use the Jepp vector database.
There was a stand-up comic on TV who used to always start with "I am going to tell you a story...." (Frankie Howerd)? I can tell you a story about a VOR receiver which would show a perfectly plausible radial, no flags showing, but it was complete rubbish. I also used to fly an Archer whose DME would show anything it felt like, but most of the time it mattered (say on an NDB/DME approach) it was usually plausible, but it was rubbish. Now, that is really dangerous because all multi-step step-down approaches are that way for terrain clearance. So, let's ban VOR and DME navigation.
As a general comment, I doubt whether more than 1% of UK PPLs read this stuff. However, the pro-GPS and anti-GPS pro-modern anti-modern conflict pervades GA very thoroughly everywhere (except among pilots who go places and who can't be bothered to argue about nonsense like this). It does not suprise me, given the wide range of types of aircraft operated, and the huge range of pilot ages. What does suprise me is the way the GA Dept of the CAA remains on the sidelines, letting it carry on. All the while approving BRNAV units, which makes a mockery of the attitudes of its (very small) GA Dept.
If the RAF still navigates this way, it is as well it is the Americans who get to do the dirty (but usually necessary) work around the world today!
Recently I spoke to a Hawk pilot (an instructor as it happens, too). He said they navigate absolutely using dead reckoning, map, stopwatch. GPS is out of the question. I asked him what would be the function of a Hawk in a real conflict. A long pause followed........ the enemy would only need to wait for some clouds to form
Droopystop
The SW corner of the 2500ft+ TMA is, measured from the displayed map
Jepp Flitemap (current Jepp vector database)
N 50 58 31
W 000 34 28
Jepp Flitemap (current Jepp "VFR raster charts" database)
N 50 58 31
W 000 34 23
Navbox Pro (current Navbox database)
N 50 58 20
W 000 33 40
Memory Map (2004 CAA 1:500k chart)
N 50 58 29
W 000 34 25
Memory Map (2004 CAA 1:250k chart)
N 50 58 31
W 000 34 27
OziExplorer (real 2004 CAA 1:500k printed chart, scanned, my own map calibration)
N 50 58 32
W 000 34 23
All the above are within the thickness of a line on the printed chart.
Perhaps someone with more time will look up the official lat/long in the AIP but frankly I doubt ALL the above products are wrong! I also know the last one above was no more "wrong" than the printed CAA chart itself because one can overlay the chart grid onto the map display and see if the two grids line up.
So I wonder just what "database" the King Air was using.
How many more GPS navigation products do you want me to dig out? I have an old Skymap 2. I also have a KLN94 and KMD550. But these all use the Jepp vector database.
There was a stand-up comic on TV who used to always start with "I am going to tell you a story...." (Frankie Howerd)? I can tell you a story about a VOR receiver which would show a perfectly plausible radial, no flags showing, but it was complete rubbish. I also used to fly an Archer whose DME would show anything it felt like, but most of the time it mattered (say on an NDB/DME approach) it was usually plausible, but it was rubbish. Now, that is really dangerous because all multi-step step-down approaches are that way for terrain clearance. So, let's ban VOR and DME navigation.
As a general comment, I doubt whether more than 1% of UK PPLs read this stuff. However, the pro-GPS and anti-GPS pro-modern anti-modern conflict pervades GA very thoroughly everywhere (except among pilots who go places and who can't be bothered to argue about nonsense like this). It does not suprise me, given the wide range of types of aircraft operated, and the huge range of pilot ages. What does suprise me is the way the GA Dept of the CAA remains on the sidelines, letting it carry on. All the while approving BRNAV units, which makes a mockery of the attitudes of its (very small) GA Dept.
Last edited by IO540; 13th Oct 2005 at 10:42.
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Thanks IO, I'll check the AIP this pm.
So where does the Radar think the boundary is?
It seems mighty strange to me that using GPS is causing an increase in infringements if the database and the sets are as accurate as they claim to be.
So where does the Radar think the boundary is?
It seems mighty strange to me that using GPS is causing an increase in infringements if the database and the sets are as accurate as they claim to be.
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Recently I spoke to a Hawk pilot (an instructor as it happens, too). He said they navigate absolutely using dead reckoning, map, stopwatch. GPS is out of the question.
Two points, first I'm pretty sure they would use a combination of GPS and INS/IRS, second at the sort of speeds the RAF would do inbound, the difference between a 10kt and 40kts is probably somewhere in the region of only 2degs of drift, so deadreckoning would probably in many cases be a viable option!!
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the GPS system is very easy to jam
If one has FOG input, one can tighten up the GPS PLL to such a degree that the jammer needs about 30db (1000x) more jamming power, than is needed to jam a plain civilian GPS.
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OK 2 more bits of data
Skyforce / Honeywell Skymap 2 (2004 Jepp vector database)
N 50 58 50
W 000 34 50
Skyforce / Honeywell KMD550 MFD (May 2005 Jepp vector database)
N 50 58 53
W 000 34 45
So far, everything lies virtually on top of each other, so I consider the King Air matter a bit of a wind-up.
Skyforce / Honeywell Skymap 2 (2004 Jepp vector database)
N 50 58 50
W 000 34 50
Skyforce / Honeywell KMD550 MFD (May 2005 Jepp vector database)
N 50 58 53
W 000 34 45
So far, everything lies virtually on top of each other, so I consider the King Air matter a bit of a wind-up.
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I remember Irv Lee (I think) of Flyer did an airticle a few years back where he skirted Bournemouths Zone using MM gps and then compared the results with the radar data. From what I remember it seemed pretty accurate.
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I agree with IO540 on this - as I said in my earlier post the simplest and most foolproof way of stopping zone infringements is by training pilots to use and equipping aircraft with moving map GPSs.
I know some will go on putting forward the age old arguments about reliability but there seems so little evidence to support these arguments. In fact there never really seems to be any evidence at all.
Consider the facts. In my experience I have never lost the GPS signal (not a single time) and I have never found my position to be any where other than that shown on the moving map. I have also never had the GPS unit fail (although I fly with two and have a third in my bag!). In the same time the VOR has failed twice and the DME once. Moreover the moving map tells you exactly what you should expect to see on the ground. Personally I would expect you to compare the ground information with the map occasionally - it really is not that hard - and there is no better fail safe.
There is a whole debate about skirting very close to CAS. However you see that debate, it cannot but help to tell the controller that you intend to skirt his CAS closely. In so doing he does know you know where you are and if he thinks you are beginning to invade his territory is likely to tell you before it becomes a problem. Whilst I don’t know the precise circumstances of the King Air bust once again had the controller known their intention to skirt CAS closely I would expect they might have warned of the infringement.
We should not forget CAS is like a prison wall keeping not only us out (without permission) but also the rest in. Whilst it is not the controllers implicit responsibility to keep us they don’t want the hassle of zone infringements any more than we (on the whole).
I know some will go on putting forward the age old arguments about reliability but there seems so little evidence to support these arguments. In fact there never really seems to be any evidence at all.
Consider the facts. In my experience I have never lost the GPS signal (not a single time) and I have never found my position to be any where other than that shown on the moving map. I have also never had the GPS unit fail (although I fly with two and have a third in my bag!). In the same time the VOR has failed twice and the DME once. Moreover the moving map tells you exactly what you should expect to see on the ground. Personally I would expect you to compare the ground information with the map occasionally - it really is not that hard - and there is no better fail safe.
There is a whole debate about skirting very close to CAS. However you see that debate, it cannot but help to tell the controller that you intend to skirt his CAS closely. In so doing he does know you know where you are and if he thinks you are beginning to invade his territory is likely to tell you before it becomes a problem. Whilst I don’t know the precise circumstances of the King Air bust once again had the controller known their intention to skirt CAS closely I would expect they might have warned of the infringement.
We should not forget CAS is like a prison wall keeping not only us out (without permission) but also the rest in. Whilst it is not the controllers implicit responsibility to keep us they don’t want the hassle of zone infringements any more than we (on the whole).
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High Wing Drifter
How much was the map adrift by?
Why was it adrift?
How many times has it occurred?
How quickly did you identify the problem?
With respect, that was my point. Pilots say GPS is not very reliable, but never seem to set out the facts.
How much was the map adrift by?
Why was it adrift?
How many times has it occurred?
How quickly did you identify the problem?
With respect, that was my point. Pilots say GPS is not very reliable, but never seem to set out the facts.
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Touch wood, I have never been lost, even for a moment, and the only time I have infringed CAS was when climbing/descending when I just clipped the three-dimensional corner of where it changes level. I've done that quite a few times.
Intentionally infringing controlled airspace was not something that I expected to be entered into the debate! Do many pilots simply "clip the corner" of a CTA without being lost?
----
With regard to the Heathrow zone case, looking at the CAA chart there is only about 2nm bewteen the Wycombe ATZ and the London CTR. Not much room for error there no matter what method of navigation is used. The gap between Wycombe and the Benson zones is much bigger and often with a radar service available from Benson. Perhaps taking a wider route (3 minute delay) and obtaining a radar service is a better strategy! Definitely better than trying to visually shoot a 2nm gap in busy low level trafic with the view available from a King Air Office!
-----
How about a VFR GPS VRP database (I love acronyms). That would probably reduce zone busts by 50%
How about everyone using the one provided by the CAA on its website!
------
Kolibear,
You are correct. makes no diference how accurate the equipment if people can't make use of such accuracy. Most people with some training can keep a CDI centered or the aircraft exactly on the GPS derived track line - provided they watch it most of the time. What happens to lookout in those cases?
------
BEagle,
Insted of expanding a zone to a line feature currently some 3 or 4nm outside the boundary, why not teach pilots that it would be a good idea to use that feature as a "handrail" to avoid the airspace. i.e. track crawl when there is a good reason for it?
-------
It does seem odd that ATC must try and keep flights 2nm minimum inside the boundary but every puddle jumper on the other side of the fence wants to get as close as possible. Perhaps we have to ask why this mindset is common? Perhaps in that culture of taking it as close as possible is the answer?
Regards,
DFC
Intentionally infringing controlled airspace was not something that I expected to be entered into the debate! Do many pilots simply "clip the corner" of a CTA without being lost?
----
With regard to the Heathrow zone case, looking at the CAA chart there is only about 2nm bewteen the Wycombe ATZ and the London CTR. Not much room for error there no matter what method of navigation is used. The gap between Wycombe and the Benson zones is much bigger and often with a radar service available from Benson. Perhaps taking a wider route (3 minute delay) and obtaining a radar service is a better strategy! Definitely better than trying to visually shoot a 2nm gap in busy low level trafic with the view available from a King Air Office!
-----
How about a VFR GPS VRP database (I love acronyms). That would probably reduce zone busts by 50%
How about everyone using the one provided by the CAA on its website!
------
Kolibear,
You are correct. makes no diference how accurate the equipment if people can't make use of such accuracy. Most people with some training can keep a CDI centered or the aircraft exactly on the GPS derived track line - provided they watch it most of the time. What happens to lookout in those cases?
------
BEagle,
Insted of expanding a zone to a line feature currently some 3 or 4nm outside the boundary, why not teach pilots that it would be a good idea to use that feature as a "handrail" to avoid the airspace. i.e. track crawl when there is a good reason for it?
-------
It does seem odd that ATC must try and keep flights 2nm minimum inside the boundary but every puddle jumper on the other side of the fence wants to get as close as possible. Perhaps we have to ask why this mindset is common? Perhaps in that culture of taking it as close as possible is the answer?
Regards,
DFC
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Well it would be. GPS, if its working, is accurate to well within the thickness of the line on the CAA chart.
I use memory map and CAA digital charts, and they are so accurate you can use them to see which taxyway (and which side of it) you are on.
People keep mentioning the CAA dB. I searched for ages yesterday trying to find it, could someone post the link here please?
ta
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It is really worrying that whenever a debate about CAS/ATC/GA etc starts we very soon have a "them and us" attitude developing. It is, I think, really untypical and the problems as perceived are from a very few on each side. Can we not have a little more understanding and sympathy from each other? Yes pilots should not fly so close to controlled airspace so that an infringement is more likely and equally ATC should be more in tune with difficulties faced at times by pilots, when the controller is sat in his warm office and the pilot is against the unexpected elements. I have flown as PIC (GA not CAT) in many parts of the world and found attitudes very different in different places. UK appears to be the worst for the them and us attitude.
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UK appears to be the worst for the them and us attitude.
I think most pilots I know and most controllers I interact with try to do their best and respect the needs of the other party within the constraints of the system we operate in.
There are some occasions, however, when it does seem the deck is stacked against everyone. I had a flight from Cranfield to EGTF where - Cranfield suggested a call to Luton (who were just too busy to get the basic call sign acknowledgement in as I transited underneath their airspace). Heathrow wasn't able to provide the Burnley/Ascot transit, meaning that I was coming in between Heathrow Zone and Farnborough’s ATZ - EGLF were trying to get a jet out and found the simplest solution was to actually clear me back into Heathrow zone Direct EGTF.
I was prepared to not talk with Luton and to not get the zone transit - however, from my seat on this day it would have been a lot easier for me and Farnborough to have done the zone crossing (although clearly I have no picture as to what challenges that might have provided to the Heathrow guys). Equally, the route is intrinsically within +/- 5 miles of a lot of zones and many of the units were too loaded to even establish a minimum level of service/contact.
Last edited by mm_flynn; 14th Oct 2005 at 09:14.