CAA Report: GPS Integrity

[Flying Lawyer]

GPS Integrity and Potential Impact on Aviation Safety

The CAA has published a report of a study of "the level of safety as measured by the integrity (i.e. trustworthiness), afforded by the Global Positioning System as a source of navigation data for civil aircraft."
The study presents "a number of augmentation methods which have been shown to have the potential to satisfy the required navigation performance requirements for all phases of flight."


It's a large file (2.9mb) so you may wish to right-click on the link, select 'Save target as...' and save the file to your computer - especially if you're not on broadband.



Link (http://www.caa.co.uk/docs/33/CAPAP2003_09.pdf)

[mad_jock]

Very interesting report.

Conclusion was again that it was unsuitable for primary navigation.

Even with such a well sourced report I am sure people will still say GPS is best.

But if they did a report looking at VFR navigation the old way, I wonder which would be least prone to failure?

MJ

[IO540]

A good read, containing little or nothing of relevance to GA.

The Volpe GPS Vulnerability report (online somewhere I am sure) is more practical, showing that a proper roof-mounted GPS aerial is pretty important to signal integrity. Everybody using a GPS should read it, IMHO.

Ultimately, one still needs to use paper charts for ground based flight planning, have a printed/handwritten plog so one can see where one is supposed to be going, and use TWO navigation methods, of which GPS being one is great.

Flying in IMC solely by VOR tracking and getting a VOR failure is no worse than flying in IMC solely by GPS tracking and getting a GPS failure. But you get a lot more bollocking for the latter.

And at the VFR level there will always be somebody who goes up without any planning and whose GPS batteries go flat, and he will be made an example of for years to come. But if he didn't carry a GPS, he would be just another fool. Not really relevant to GPS!

[Fly Stimulator]

In the interests of saving bandwidth while we have this discussion again, I offer the following options which can be used in the same way as the numbered menu in a Chinese restaurant:

1. GPS users are either lazy, or incompetent navigators or poorly trained or all of these things.

2. It is acceptable to carry a GPS as an emergency aid, but it should only ever be switched on as a last-ditch alternative to calling D&D. Primary navigation should always be carried out with compass, stopwatch and lines on a chart. Radio aids are acceptable at a pinch, but proper pilots should always fly by dead reckoning alone.

3. All navigation aids are acceptable for primary navigation, except GPS which isn’t because you are almost certain to bust CAS or get lost when the batteries go flat, you get the co-ordinates wrong, somebody jams the signal, or all of these things happen.

4. GPS is acceptable as a supplement to a PLOG and lines on a chart and is no less suitable in this role than traditional radio navigation aids.

5. GPS is suitable for primary navigation on its own. In order to stay on the right side of the law, you might consider keeping a current chart somewhere in the aircraft.



Mine's a number 4 for what it's worth.

[mad_jock]

Well at least I learnt what a RIAM failure is or whatever its called.

Maybe I won't put any effort into working out how to turn it off.

Comes up on a pretty regular baises as well. Which gives me the unfortunate conclusion that the GPS isn't as accruate as people think quite alot of the time with out them knowing about it.

H'mm how about no lines on a chart (which is store behined the seat), plog and using radio aids and GPS for navigation ;)

MJ

[Fly Stimulator]

H'mm how about no lines on a chart (which is store behined the seat), plog and using radio aids and GPS for navigation

Always someone who wants something that's not on the menu. I'll have to check with the chef.

[boomerangben]

Fly Stim...

I'll have a number 4. Can I get a fried rice and NVG on the side?

Interesting article in this months Practical Boat Owner that basically says sail with out manual nav at your peril. GPS satelites are getting older and their 3 levels of redundancy more or less depleted. Apparently at various times over the last year or so, signals in Scotland have on occasion been up to 40km out and a mile or so out on the south coast. At that was reported by a yacht in harbour!

[IO540]

MJ

In 300 hrs with a GPS (KLN94B) I've never seen a RAIM warning. If yours doesn't have a rooftop aerial, it will have marginal performance at best. What model is it and how old is it? If your aerial is on the roof, is it an active one or a passive one? Do you always load the QNH into the GPS at startup?

FS

I agree with #4, in the PPL context.

For IFR, GPS/VOR/DME/ADF concurrently, whatever is available, plus the plog and the chart. The GPS course on the map display is the primary reference and the others must confirm it. Shame PPLs aren't taught to fly that way too.

boomerangben

You can always find these stories from somebody. Was it an ancient GPS with an internal aerial, used below deck perhaps?? Or did they enter a user waypoint and got a couple of digits transposed?

[S-Works]

Oh god I am losing the will to live. Another GPS debate!!! :p

Have to agree with IO540 here, several hundred hours of GPS usage and never seen an error. I always fly radio aid, VOR/DME/NDB in parralell to the GNS430 which is connected to my altitude encoder (amongst many things) and they have always given the same story, unless of course the steam gauges are wrong as well........

Of course I always draw a line on my charts and have a PLOG (I need somewhere to put the R/T frequencies and QNH etc.

And of course when flying IFR I just draw a track on a blank piece of paper...... :p

[The Nr Fairy]

bose:

"several hundred hours of GPS usage and never seen an error" - your perception may well be that, based on a small sample of the overall GPS availability, every time you go flying GPS is available with minimal errors.

Aviation being the conservative pursuit that it is, I'd suggest your sample of GPS error rates is a little on the low side.

[S-Works]

TNF,

You could well be right but I fly on average 350hrs a year which equates to around 30hrs a month which is not a bad exposure?

Unless others like IO540 are flying at the exact same time as me then they have further exposure and don't seem to be experiancing problems either.

The only time I have ever seen an error in GPS on my boat was when we had a faulty antenna connector which had corroded in the sea air. The loss of satelite coverage due to the unit going "blind" gave position errors that were still within about 300m.

I have also never recieved a RAIM warning on my GNS430 which is certified for BRNAV. I have certainly suffered far greater errors on an NDB do to the usual problems of atmospherics etc.

I am more of the view that people find a reason to fault GPS rather than embracing it as a usefull tool.

I do consider the person who trundles off with a handheld GPS and no map a fool, whereas the person who uses all the tools availble to them is very smart.

[mad_jock]

Gods knows m8, Its either a Trimble or Bendix and its an area GPS fitted to a pref A machine, certified to be used in controlled airspace.

THe GPS drops out a fair bit round here especially when GMC is running on the west coast.

FRA planes are jamming it off and on. Sometimes with a NOTAM sometimes without.

But the RIAM warnings havn't just been in the North of Scotland. Have had them in the North of England as well but again that might be FRA up to there usual tricks out of teeside.


MJ

And I am flying about 20hrs a week.

[Johnm]

I like belt, braces and a piece of string to maintain my dignity. I also like to use all the kit I can lay my hands on while flying.

This weekend I was flying with PLOG and chart (with lines), one built in GPS one handheld GPS RMI HSI and VOR and because I get as much as possible set up before I leave the ground and there's an autopilot I can still find time to look out of the window!

What I use depends on where I am, so I might be using VOR and cross checking with GPS or I might be using GPS and cross checking with NDB. The fixed GPS doesn't have moving map, so the handheld is good for helping spatial awareness and if I can see out of the window I can cross check with the chart and lines!

Use the best available tools for the job in hand is my motto and never ever just rely on one!

[IO540]

MJ

Sadly, without more info, one cannot really take that info as being worth anything. Just because some installation was once certified doesn't mean it's any good. How do you know an aircraft is jamming it? Have you been out with the equipment and detected the jamming, or do you have some inside line to the military?

I've flown in enough planes in which the GPS was nearly falling out of the panel. Yes, I expect it worked just fine once upon a time. Doesn't prove anything.

TNF

That's the same old anti-GPS story you are spreading, without support.

I know it's a waste of bandwidth but people who spread these stories are doing a dis-service to GA.

I do about 150hrs/year, have never seen a RAIM failure, have never been uncertain of position, and this is UK, France, Spain.

Incidentally, and this might really get the anti-GPS crowd going, I have never seen the GPS altitude to be more than 50ft off, in any location where I knew the exact elevation (i.e. on the ground at an airfield). It's also spot on aloft, once one has adjusted the altimeter for the deviation from ISA. Not that I use it for that.

[yakker]

American military aircraft based in the UK use GPS as primary navigation, and how do those cruise missiles hit the target if gps is unreliable?

[S-Works]

Not to mention that fact that most surveying these days is done with GPS as well!!!

[QDMQDMQDM]

Two potentially useful thoughts from a recent trip to the Antarctic on well-equipped Russian boat.

1. The Falklands are currently being surveyed using pairs of (interferential?) GPS's, accurate to a couple of centimetres.

2. The ship's crew used radar cross-schecked with the chart, not GPS, for going in and out of anchorages, day or night. They used only GPS for en route navigation and used the sextant once a month for practice.

I'm with FS: Option 4.

QDM

[mad_jock]

God knows the legalities and checks involved in a BRNav GPS fitted to a commercial airliner. If it lights up and the card is valid it gets used.

And the Mil do publish the times and areas which they are jamming via NOTAM.

To be honest this has already turned into those that swear nothing ever goes wrong and those that don't think they are quite as good as some make out.

Reports can be written at vast expense and people will still say "well i have never had a problem" so its bollocks or doesn't apply to me.

I am quite sure in 50 years time we will be having a similar debate about panel mounted INS systems in light aircraft.

And as the report points out the current set of hardware in orbit is rapidly reaching its sell by date. And who knows what the next system will bring. Considering the cost involved I wouldn't mind betting some where along the line users will be getting charged a liscense fee to use it. And the americans don't even have a viable launch system at the moment so any progam to undate the hardware is on hold.

MJ

[Evo]

Claiming that GPS is too unreliable for primary navigation but that the NDB/ADF combo is fine seems a bit daft. I've tried to use an NDB as a navaid a few times (IMC training and post-PPL nav) and have never been very satisfied with it - the list of errors is well known, and it's a bit much when you're two miles from BIA and the ADF needle is 90 degrees out. VOR is fine, but I was well into the IMC before I stopped making stupid mistakes with it. That system is OK, but the user (at least in my case) wasn't.

I would have thought that GPS is similar - errors and failures aren't that much of a problem compared to simple finger trouble and lack of understanding. I'd bet for every airspace bust due to some mystical RAIM failure (whatever that is) there have been a dozen or a hundred from people hitting GOTO and going in the wrong direction. IO540 and bose-x may just be unusual in that they understand the box and can work it correctly... :)

[IO540]

MJ

I was merely pointing out that someone saying (paraphrasing) that Joe Smith, 75, was sitting on his boat sometime last year and 6 months later reported, over not a few pints of Guinness at the Rose and Crown, that his trusty old GPS wasn't working for half an hour, doesn't amount to good evidence of GPS unreliability. Yet this is the sort of "evidence" we get all the time.

A few high-hour pilots on Prune saying they've never seen problems doesn't amount to categorical proof of GPS reliability, but it's a whole lot better supported than the above. From my own point of view, I know a good number of IFR pilots with modern "IFR GPS" gear (which, in the UK basically means KLN89/90/94, GNS430/530) and none of them has ever had the slightest problem.

There are reports quoting frequent losses of accuracy, say from 20m to 200m, and make a meal of that. But for en-route navigation, 200m is NOTHING, zero, zilch, utterly irrelevant. And one cannot use GPS for anything else other than en-route (yet). GPS accuracy could be degraded an order of magnitude and nobody in GA would be affected - although it would show you on the wrong taxiway :O

The U.S. economy is heavily dependent on GPS now. They won't let it fall apart. Who says the system is reaching it's sell by date? It works perfectly well.

The Europeans will have Galileo to give them theoretical independence from the Americans (always a good topic on which to get the Brussels crowd working on yet another device to immortalise themselves) but they will charge for the high accuracy signal. Not that that matters, because the GPS, even with its worst errors due to selective availability, was miles more accurate en-route than anything else. But your airliner IRS will sync from DME/DME anyway, whenever it can.

I sincerely hope that fibre optic gyro IRS will reach GA long before 50yrs from today! The JDAM package reportedly goes for about US$20k and that has a FOG IRS, a jam-resistant military GPS, servos, you name it.

EVO

Yes, I think training is the #1 problem. But the powers to be, as well as much of the old crowd, have dug themselves so deep that bringing it in formally is just about impossible.

Putting a GNS430 or similar in a plane flown by a new PPL just makes matters a lot worse... but that's what happens when technology moves along but the regulatory powers pretend it doesn't.

The best single thing the CAA could do now is mandate a rooftop GPS aerial. But then they would be admitting that GPS is OK to use in some circumstances, and they can't possibly do that... and lots of people would be sure to moan about the £500 cost. And they can't be seen to regulate portable equipment so they would have to mandate a panel mounted unit, and who will pay for that? It's Mode-S cost, roughly.

[S-Works]

EVO,

I do actually understand perfectly how the box works and to be frank it is actually very simple. Or maybe I have a brain the size of a planet....:cool: :cool:

[The Nr Fairy]

I think I'm one of the option 4 candidates.

Until recently, when I started flying aircraft with the payload to carry a GPS, I'd never used one. So, line on a chart and cross-referencing it is too.

About the reliability thing, I'm sure that it is a damn sight more reliable than a lot of other, quainter, navaids and in VMC I can't beat it for telling me how lost I am. I'm unlikely to become an IFR person but if I were, the other 23 hours in the day when you're not using GPS may be the times it has problems ?

IO - I'm not "spreading an anti-GPS story", nor am I anti-GPS, merely trying to point out that 350 hours out of 8000 in a year isn't a big enough sample to convince me to rely totally on it - much the same as a lot of other people.

[Evo]

Yes, I think training is the #1 problem. But the powers to be, as well as much of the old crowd, have dug themselves so deep that bringing it in formally is just about impossible.


It's true that there's not really an obvious place for GPS training in the PPL - it has enough content already, and personally I believe the VFR Nav must be learned, if just in preparation for the day you find yourself with no power in the aeroplane.

I guess you could add some GPS theory to the PPL Aircraft Technical exam, but why not have some kind of basic post-PPL "differences training" (coupled with an associated avionics-quality requirement) that allows you to use GPS as a primary navigation aid? That way there is a basic check that the user understands the kit well enough to avoid the most simple mistakes - and that IMHO is the real problem with GPS. As the price of a receiver drops below the price of an hour in the air I can't believe it will be ignored forever.

We cannot fly IMC or tailwheel without demonstrating competence. Why not the same thing for GPS as a primary navaid? Those with decent kit and a sign-off can join the 21st Century, the rest of us can carry on with a Pilot III as backup.

[paulo]

Quick word to the unwise: Don't do what I did... carry it in your pocket thinking eyeball one was the trick, then in the soup when you want it, realise you can't pick your way through the menus whilst trying to dodge the crud.

[reynoldsno1]

The paper is concerned only with IFR operations and GPS. It is years behind what is happening in most other places in the world, and is only applicable to the UK.

We shall continue using our RAIM prediction service to help carry out safe non-precision GPS approach procedures, like we have for the past 10 years or so..... :zzz:

[FNG]

I also go for Fly Stim's number 4. Devising a standard training component of the PPL (or add-on package: I like Evo's idea of a form of differences training) might be a bit tricky, because of the variations in available kit, but the problems would not be insurmountable. I expect that we shall see this emerging quite soon. I think that Irv Lee and others already offer post-PPL GPS-nav courses, emphasising the ancillary benefits of the technology in terms of fuel management and so forth.

Meanwhile, one of these days I really must learn properly how to use my GPS, instead of simply using it as an occasional backup, although I must confess that I'm one of those weirdos who obtains a perverse pleasure from flying by DR.

[bar shaker]

I read the report as a PR exercise to justify Galileo.

US system = old, bad, unreliable
US+EU system = sweetness and light

I'm also an option 4 and until I get errors or loss of service, I will carry on using it as an integral part of my navigation.

BS
(who went to school in the days when you weren't allowed to use calculators)

[IO540]

FNG

I read a writeup in some UK flying mag c. 1yr ago saying that AOPA were working on add-on modules for the PPL, and GPS nav was to be one of these. Crucially they said the pilot would get some sort useful piece of paper at the end. Heard no more about it.

Once I went on a 1 day Honeywell GPS ground school, and I was the only one who turned up! One needs to give people something tangible. But what? GPS usage is unregulated so why attend any course? It's a catch-22.

If every school plane had a nice big panel mounted (e.g. a KMD150, not the much more complicated GNSx30 etc) colour GPS but you had to attend 1 day's ground school to be allowed to use it, most people would go right away, I bet. Cost to properly fit one of these is c. £3000.

To many people, loading a flight plan into a moving map GPS, either directly or from a PC (the latter is not possible with most panel mounted units), is trivial and takes only minutes to learn. These people are unlikely to ever get lost, basically because it is damn difficult to do when you've got a preprogrammed track in front of you, with pictures of towns, roads, railways, and CAS depicted around it. But others seem to really struggle. How did they get through their PPL exams? Is it just those people who get lost despite having a GPS?

The people that do the most serious CAS busts get interviewed, and I am sure somebody has this data, and for some reason they aren't publicising it. My own belief is that those that get lost with a GPS are people who were using a non-moving map model and didn't understand it's rather obscure display (I know I wouldn't automatically). But what we get instead is a load of bunk (see CAA safety sense leaflet #25 for example) telling everybody about "terrain shielding" etc...

The whole matter of GPS has been very badly mishandled, I think.

[FNG]

The AOPA chit route could work. Consider the AOPA Aerobatics Certificate: this is unofficial, as no special licence or rating is required to fly aeros, but over the years the AOPA course has gained customer recognition as the standard intro to the discipline. A GPS course, sponsored by AOPA or someone else, could acquire similar kudos over time. I would expect to see GPS-nav being incorporated into the PPL syllabus within a few years in any event.

[robin]

So what sort of format would be taught in a GPS course.

Would it require everyone to use, say a specific model, say a 196 or a panel-mounted, roof-aerialled and with runway and approach capability??

GPS's vary enormously in terms of display and capability, as well as the depth of wallet of the pilot. That would all have to be taken into account

Looking at previous GPS correspondence you'd never agree a course to fit all users, from the PFA and gliding fraternity to the heavy-duty IFR users.

There is a useful little manual produced by the BGA on basic GPS use - but I think that is based on an early Garmin - the 12 I think. It gives the basic principles but won't go as far as modern equipment will permit.

In my career to date, the hardest problems I have had have been getting to know the radio kit in each new plane. No standardisation, lots of switches and knobs in different places on the panel etc. Now we have different GPS types to add to my confusion ........

[Evo]

A GPS course, sponsored by AOPA or someone else, could acquire similar kudos over time.


I agree about the success of the AOPA aeros course, but I think it's probably a success because self-preservation dictates that virtually all pilots would take some training before flying aerobatics. It's a well-structured course, and there's nothing else out there.

The AOPA radio-nav course is very good for those who would like to use radio navaids to help fly themselves around, and would arguably be more sensible than an IMCR for many people who take an IMC with no real intention of using it "for real". However, few people seem to do it and I would suspect that an AOPA GPS course would suffer a similar fate.

I think any GPS "rating" would need to be more official; remember though that I'm talking about something that would allow you to use a Garmin 530 as a primary navaid (in the same way that you could use a VOR), rather than a blanket requirement for every PPL with a pocket GPS.


So what sort of format would be taught in a GPS course.


I'm thinking of a (fairly) model-independent demonstration of competence, using the simulation mode to do some basic tasks - diversions etc. - and some classic gotchas like the famous invisible N866. Probably not some of the fancy IFR features (they could be included in an instrument refresher?). Something a bit like the FRTOL practical, maybe, and at similar cost? Like the FRTOL it could be complete self-study or you could use taught courses. Any "rating" would be valid only with a sufficient avionics installation.

[UL730]

Went to an interesting Royal Institute of Navigation lecture on SatNav for General Aviation some years ago. Got lost in Helmert Transformations and Molodenski Formula, which was ironic, but a very interesting chap called Huw Baumgartner from CAA/NATs summarised the CAA’s position on technical issues.

He made 3 navigational equipment system definitions.

A Sole Means Air Navigation System – approved for specific phases of operations. VOR/DME is an example.

A Stand Alone Air Navigation System – is not combined with other navigational sensors or systems. It gets no help from another source such as when an IRS is updated by multi DME - DME.

A Supplemental Air Navigation System – is an approved system that can be used in conjunction with a Sole Means System.

The GA community is looking for an approved Stand Alone – Sole Means – cleared for enroute and approaches- viz. GPS. The difficulty here is that the signal is weak and subject to in band interference and out of band interference. The former relates to problems at or near the propagated signals spectrum – satellite comms systems for example and in the latter case, transmissions on apparently remote frequencies that interfere with the signal. Harmonics on VHF frequencies such as the thirteenth harmonic of Gatwick Approach falls in the middle of GPS spread. Arc welders also have an interesting effect!

The CAA’s position is that GPS is a Supplemental System when approved.

Wilful interference is a key topic that is no doubt being addressed by security agencies. An ice cream van fitted with a jammer the size of a shoebox could, if sited on Hog’s Back in Surrey, could render all GNSS approaches inoperative, at all South East UK airports. These are the times we live in.

The conclusion was that CAA is supportive of satellite based navigation but it has to be conducted at an appropriate level of safety. Safety in a security context seems to be a moving and political target. The provision of a dedicated European satellite in the near future to provide a form of WAAS is eagerly anticipated.

I use a B-RNAV approved GPS for enroute navigation. I get at least one RAIM failure per flight on average. They don’t last for long and other non approved GPS installations in the A/C give no indications other than they are fat and happy – whilst the main GPS is red flagging the HSI and beeping away like a good ‘un.

Came away from the lecture committed to always fly a Sole Means Air Navigation System side by side with GPS.

[IO540]

No matter what one does, GPS can always be jammed eventually.

But one can make it very hard to do.

Rooftop aerials (essential for a decent reliable signal, anyway) help a lot from ground-based sources and also with interfering sources on the same metal aircraft (e.g. DME aerials being on the bottom). Anybody can do this, and everybody should. If I was the CAA, and I wanted to formalise GPS somehow, I would make rooftop aerials mandatory. It's relatively cheap. Anyone using a handheld with an integral aerial, inside an all-metal cockpit, is asking for trouble. Unfortunately these units do work 99% of the time :O

Introducing IRS data into the GPS receiver enables one to make it far more resistant to jamming - even if the IRS gyro has poor long term accuracy. Reasonably priced FOG-gyro attitude instruments already exist so this isn't far away.

Aerial polarisation is another technology not yet available to civilian users.

Other anti-jam technologies require more processing power but you bet the military have them. It's pretty easy to work out how to do that, too.

One essential point is that if a modern GPS is unable to compute a good solution, it says so. Identing a VOR or NDB or DME just tells you you've got the right frequency tuned; it says nothing about the instrument being useful. I've flown with VOR and DME kit which could be made to read anything, and yes they were within the DOC.

But I bet ILS will be with us for decades to come :O

What I don't get is why so many people keep assuming that GPS usage implies using it as a sole nav reference....

[boomerangben]

Sorry for bringing this one back from the dead

IO540 wrote:


You can always find these stories from somebody. Was it an ancient GPS with an internal aerial, used below deck perhaps?? Or did they enter a user waypoint and got a couple of digits transposed?

The somebody that wrote the article is a vice president of the Royal Institute of Navigation.

The article goes on to point some of the other problems with GPS, including weak signals, interference and jamming. It is interesting to note that the European Maritime Safety Agency is looking at the use of LORAN C for back up to GPS.

GPS is great and should become part of the nav part of the ppl, but you should always be able to tell when it is telling porkies, in other words, be able to gross error check your position using the chart or other nav aids.

[IO540]

GPS is great and should become part of the nav part of the ppl, but you should always be able to tell when it is telling porkies, in other words, be able to gross error check your position using the chart or other nav aids.

and I have never said otherwise!

[A and C]

As far as I can see it the knee jerk reaction from the CAA has always been anti GPS and when the first hand held units showed up with power from the cigar lighter socket , the anttena stuck on to the windsheild with a suction cap and lots of wires to trip over in the cockpit I could see the point of this attitude.

Move on ten years and B-RNAV is mandatory above FL100 and 99% of the B-RNAV units are TSO GPS units , the rest of the world is doing GPS NP aproches and still they are sticking to the GPS is not 100% safe line !.

First let me tell you no machine is 100% safe but with the way the leagal system works in the USA do you think that the FAA could afford to approve such a system if they did not think that it was safe for every day use .........I think not !.
The USA is the biggest user of GPS on the planet and do we see the States littered with aircraft that have crashed on GPS approches ?. I would also like to know What the GPS vs NDB approach accident rate is as I suspect that the numbers would show that the CAA attitude to GPS is increasing the risk of an accident.

The problem is political not technical the CAA have dug themselfs into a hole and cant find a way to crawl out just like when they over reacted to the Lycoming crankshaft corrosion problem costing people tens of thousands of pounds , I see that they have quietly withdrawn that AD in favour of the much more sensable FAA AD now that no one is lightly to take leagal action.

The lycoming engine problem is a simple one involving a lump of metal and a lot of data that the CAA could no longer argue aganst and belatedly when all danger of the legal action was passed they conceded to the hard facts , the GPS debate is far more complcated and they can sit in the Gatwick glasshouse for years to come ignoring this the GPS reality and thinking that they are the world power in aviation legislation but they have supervised over the compleat demise of the Brithsh aircraft construction industry I just wonder how long it will be before no airliner in the UK carries a "G" plate because of the obsticals that the CAA places in the way of progress.

[High Wing Drifter]

But if they did a report looking at VFR navigation the old way, I wonder which would be least prone to failure?
Agreed, but at least with a map,compass and stopwatch you know when you are lost.

FWIW, I seldom use our GPS (a Skypmap IIIc) and still I have seen it twice place the aircraft a few miles from where it actually was.