Mike Cross

And you'd be amazed how many of them have a knob marked OBS as well.
It's usually the loose nut on the yoke that causes the bust, not the Nav Equipment.

nipper1

Great thread. Even more uninformed rubbish than usual.
As it happens I know quite a lot about GPS accuracy (I have spent the last two years deploying GPS in a non-aviation application and actually testing the accuracy of various commercial units both statically and dynamically) but I won't bore anyone here with what I have found out as it would spoil this thread....
Suffice to say, the problem will almost always be with the operator and not the kit - as it was last time I dialed '190' into my VOR instead of '170' and ended up somewhere I did not mean to go.....

Fuji Abound

Nipper1

Oh no, please do bore us!

There is so much disinformation written about the unreliability of GPS from the "anti" lobby that I think it would be a great contribution to this thread to read your findings.

chevvron

Nipper 1; is it true that GPS for car use depend on a DGPS signal transmitted from commercial radio stations and 'piggybacked' on their transmissions?

High Wing Drifter

I'll second that!

funfly

I flew on a 100 bearing today instead of an 010. nearly went into an ATZ (true story)
Fault of a useless compass of course, you just don't trust them

Johnm

For the record I'm a GPS fan. If I've got a panel mount it's my primary nav facility and it works more reliably and more accurately than anything else on the panel including the FM Immune VOR/ILS (which works no better than the none immune one but that's another story)

The only caveat on GPS is the issue of relying on the database to be both up to date and accurate when it comes to airspace (they usually are if regularly updated but not always) so there's a need to xref a current chart and NOTAMs but that's routine flight planning ain't it???

For hand helds extra caution is required because they will lose coverage from time to time depending on how uniform the view of the constellation across the sky happens to be. Early morning East bound near Luton seems to be a problem at present in this respect

funfly

Johnm
We're all with you.

shortstripper

for the record I'm not anti-GPS, but still find it rather too all encompassing to say that the "answer" is GPS! Users still bust airspace! Yes it probably is the fault of the user, but it's the growing reliance on GPS that is most worrying. Before much longer it feels like traditional ways of navigating will be dumped in favour of this perfect solution to our navigating woes. As the son of (and myself at various times) a professional fisherman, I can say that the introduction of GPS was a revelation when compared to the old decca system. However, GPS still occasionally loses itself during certain atmospheric conditions, rough seas or electrical circuitry problems. Ok, these are tiny things and most unlikely ... but they do happen. I even remember once (when airbourne GPS first came in I admit) hearing a pilot disputing that he was somewhere other than where he thought. he said something along the lines of "this GPS cost two thousand pounds ... it can't be wrong" to which the controller curtly replied "well this radar cost twenty million ... do you think it is wrong"?

SS

IO540

The only caveat on GPS is the issue of relying on the database to be both up to date and accurate when it comes to airspace (they usually are if regularly updated but not always) so there's a need to xref a current chart and NOTAMs but that's routine flight planning ain't it???

I would normally agree you need the printed chart for VFR planning but not for the accuracy. Your chart can be up to a year out, and notams of changes will be in the notam database only until the next AIRAC cycle i.e. 28 days. So if the chart is dated say Jan 06, there is a change 01 Feb 06 and you don't fly the relevant airspace during Feb then you will never know about it. Whereas with GPS databases you have the option to know.

The fact that it costs a lot of money to update is a separate issue, but it can be minimised, e.g. if you are doing a long trip around Europe then you have a choice of

a) buying a load of printed charts, which will be anything up to 2 years out of date

b) updating the GPS database, which will be at most 28 days out of date

For VFR you do both. For IFR (airways) you buy a few airways charts, dirt cheap, and do a one-off database update, but we aren't talking about IFR here.

It's a tough one because CAS depictions on GPS databases have poor clarity; only just good enough to relate to the paper chart on your lap. But, if the two differ materially then it should be obvious there is something wrong.

For hand helds extra caution is required because they will lose coverage from time to time depending on how uniform the view of the constellation across the sky happens to be. Early morning East bound near Luton seems to be a problem at present in this respect

I doubt there is anything in this. There is no correlation between the GPS satellite constellation, early mornings, and Luton Maybe you have marginal reception and are getting zapped by radar or something.

A current-model handheld with a rooftop aerial will be as good as any panel mount with a rooftop aerial.

Before much longer it feels like traditional ways of navigating will be dumped

The correct thing to do then is to donate them to the British Museum, not fly with them. My heart really bleeds for these wonderful old traditions.

As I've said before 50 times, there is no way navigation is going to improve as long as people are expected to be doing dead reckoning. Unless the CAA donates £5,000/year to each PPL every year for currency, which it won't. Just about anybody can get a PPL if they are willing to survive a year's worth of UK training, and "just about anybody" isn't going to get any better tomorrow than they are today. The only options left are to more carefully select the pilots (which the training industry will be dead against), train them more rigorously (comment as before), or use different methods. GPS is the best method known by far; nothing comes even close.

Johnm

Actually the wee beasty is normally very reliable completely unmoved by proximity to radar or Hirta sites and it's possible that there's gaps in the constellation it can see through the windows 'cos of failed satellites. It used to be perfectly reliable in this particular area too. However I can't claim to be a serious expert in GPS infrastructure.

IO540

The constellation isn't geostationary; it moves about all the time. So there can't be location-consistent coverage gaps.

There is a website where you can get coverage quality (RAIM) prediction for a given lat/long location and time, or an IFR GPS can work it out for you. But as I say it varies with date and time.

englishal

HDOP and PDOP spring to mind........

Which the GPS tells you

DFC

IO540,

Your statement regarding updating the aeronautical chart to make it legal is incorrect.

AIP:
Before using any CAA chart operationally, users must determine what aeronautical changes have taken place since its
validity date and amend the chart accordingly. This will require users to consult all UK AIP amendments issued since the charts validity
date. If in doubt, they should consult AIS Central Office. A list of amendments for the VFR chart series is available on the CAA web
site: www.caa.co.uk/dap/dapcharts

It is not a useable chart unless the relevant updates have been incorporated. The CAA website not only lists all changes but will often have advance warning of future changes.

Other countries will have their own system, many of them will include the hand amendments in the AIP. Jeppesen have a chart notam series updated weekly.

IO540 said: There is a website where you can get coverage quality (RAIM) prediction for a given lat/long location and time, or an IFR GPS can work it out for you. But as I say it varies with date and time.

Will your IFR GPS tell you in advance that sattelite 30 will be u/s from 15:15 tomorrow until 03:15 on 1st March?

-------
I can't hear - the medical limitations for hearing are wrong.
I can't differentiate colours correctly - the medical standards for colour blindness are wrong.
I can't navigate by DR - GPS should be the way to navigate.

Deaf, Dumb and Blind pilots should not be discriminated against

Regards,

DFC

englishal

.....there are a few Dumb pilots on these forums, thats for sure

boomerangben

Can't we just make up our own minds about how to navigate? What suits some might not suit others.

I fly SAR. We use GPS extensively. We also make use of VORs, (OK only very rarely but that is due to altitude and location) NDBs, DME and DR (albeit calculated by computer from a Doppler unit). We also spend much of our time eyes out with a chart on the lap. We train to navigate low level over featureless landscape to find a pile of rocks without the GPS. GPS may be accurate enough, but cartography is not. We would be mad to simply use GPS to get us to a casualty at the bottom of a cliff/half way up a mountain. GPS gets us to the ball park then we use the eye ball. The GPS is also backed up by mandraulic DR for gross error checking. In other words all means of navigation have their place in aviation. OK we are perhaps ususual in that we use all of them.

It is vitally important that all VFR pilots can read maps and charts. Learning traditional navigation techniques helps that learning process. Shamefully it is poorly taught at PPL level. Partly because we are all a little bit gadgety, partly because no one taught the instructor to navigate properly, partly because we want to fly not study when learning to aviate. With a little more time, map reading could be made more accessible and easier.

IO540

DFC

Like most of your more technical postings, you are describing an ideal world which in practice doesn't happen. Pilox X buys a chart from his local pilot shop and flies with it. He buys the next edition the following year, etc.

Translate that situation to going outside the UK, where you deal with potentially a multiplicity of charts, some (e.g. Greece) not updated for 5-10 years. Electronic databases like Jepp are the only way to get up to date chart data for a lot of places in Europe.

boomerangben

I don't disagree, but in your case IF the person you are rescuing had a GPS and was able to transmit the lat/long to you using some means which doesn't involve speech, your job would be a lot easier. Know about EPIRBs with a built-in GPS? If you can't use the signal then a lot of your capability is pretty sub-optimal.

To clarify: a lot of this pro- or anti-GPS debate is really the modernist v. traditionalist debate. "GPS" just drags the respective protagonists out of the woodwork.

I have no problem with somebody who wants to fly traditionally; it's their business entirely. If you want to fly like Charles Lindberg, right down to wearing exact Lindbert replica underpants, I admire you for the effort and wish you success. I have just spent some time in Arizona, where the most modern turboprops/jets with all the gizmos coexist happily with wood and fabric aeroplanes from WW1, all on the same airfield, and often flown by the same people.

But if the objective is to make a dent in the few-hundred CAS busts that were reported last year, it's no use pretending that "better training" is the answer. Well it might be but it won't come about.

It's equally no use pretending that pilot X is suddenly going to navigate reliably by dead reckoning, when (like most people) he has been having problems with it beforehand.

shortstripper

But he/she will buy a GPS and learn how to use it properly?

SS

DFC

IO540,

I just love the way you dismiss legal requirements that are easily and simply met as some form of ideal that can be ignored. Obvoliusly you did not ignore that ideal (legal requirement) because you did not know about it. Now you do. Isn't learning fun.

You also ignored the comment I made about the RAIM perhaps you would like to anwer that question?

--------------

boomerangben,

Well said.

Regards,

DFC

boomerangben

Of course the incidents where we get a GPS derived positions are much easier, but onshore at least, they are few and far between. We are usually relying on Joe Public's map reading abilities. The GPS/EPIRB combination is wonderful though not as widely used as it should. Many of our jobs are onshore or coastal. The GPS is great for getting us to the locale, but for situational awareness, planning the operation and setting up an approach to the casualty's location is best done using an OS map. The GPS will take you to the exact position, but it will not tell you what to look for or indeed if it is the right position. Nor will it tell you that you are about to hit something hard or stringy.

Of course for many PPLs the GPS is adequate, but you can navigate very well without one (in my opinion just as accurately). In some situations the GPS is preferable to map reading, in others, map reading is more suitable. Yes, map reading is a hard won skill, but it is wonderfully satisfying and adds a bit more interest and challenge to private flying.

To say one is better than another is like saying apples are better than oranges. To say that PPLs shouldn't bother learning about a valid nav technique is like not teaching an apprentice carpenter about the different types of saw.