GPS Down?

[Ludwig]

Where are the GPS satellites? Used my GPS on Saturday without problem, tried to use I on Sunday flying from the Midlands to Norwich and nothing absolutely zip. Tried it in the car this morning, still zip. The unit switches on and does everything except get satellites. Before I run screaming to Garmin for help, have I missed some major GPS jamming? Did anyone else have similar problems?

[charlie-india-mike]

GPS worked just fine for me yesterday 13:00 to 15:00. First time I had flown an aircraft with a decent GPS system. Must fly that one again .

C-I-M

[Davidt]

Flew 5 hours yesterday NW to SE and back again GPS fine all day.

Look at your ariel.The standard portable ones supplied are cr*p!

If you can get one fitted to the aircraft.
I used to loose signal all the time using a Skyforce and the suction cup ariel. Since installing a panel mounted model and fitted ariel the thing has not so much as blinked!

[Wee Weasley Welshman]

Likely the aerial connection - is it a PilotIII by any chance?

WWW

[Ludwig]

WWW no, it's a 196 which to date has been the dogs roundthings

[WorkingHard]

The above leads to a question - why does one have to pay a radio licence fee for uninterupted (i.e. monitored and secure) and then the "authorities" allow the military to jam the signals? Are they in breach of the agreement?

[Chuck Ellsworth]

When do the military jam the GPS signals?

And where do they do this?

[BRL]

Davidt, Was that you flying Tango-Tango yesteday?

[Evo]

Chuck -

"When do the military jam the GPS signals?" It's quite frequently NOTAMed in the UK - often with a large radius, e.g.


AC 5555
07 JUL
1100-1400 30000ft (A1063/02pt)
08 JUL
0715-1015 30000ft (A1063/02pt)
GPS Jamming Activity 5555N 00550W rad 320nm


see http://www.pprune.org/forums/showthread.php?s=&threadid=58536

"And where do they do this?" Off the top of my head I can remember Scotland, a NATO exercise in the Iceland-Faroes gap and the Bristol channel. As I said, it's quite common.

HTH

[Davidt]

BRL

No flying Fox Tango, G-OLFT.Liverpool - Midden-Zeeland and back.

What i do wrong paranoid!

David t

[StrateandLevel]

The UK military consider it acceptable to conduct GPS jamming trials on the grounds that GPS does not operate on an internationally allocated frequency for navigation equipment.

[NorthSouth]

Could this be an explanation for the CAA's negative attitude to approving GPS for navigation? If they did, the military would have to stop jamming it?

[Unwell_Raptor]

After all, the military paid for it, put it in the sky, maintain it and let people use it.
So if they want to play with it - it's their trainset.

[FlyingForFun]

NorthSouth - why would it make any difference if GPS was approved for navigation?

ILSs, and to a lesser extent VORs, are regularly taken down for maintenance, etc. There are some NDBs which have been out of service for longer than I've been flying (which isn't all that long, but it's long enough to fix an NDB!) As long as it's properly NOTAMed, there's no reason why any navigation system shouldn't be taken out of service, especially if an alternative is available.

FFF
----------------

PS - UR, wasn't it the US military who did all those things? Can't see what relevance that has to us in the UK :confused:

[NineEighteen]

The US DoD occasionally used to activate 'Selective Availabilty' which would degrade the accuracy of GPS for non-US military (or non-authorised) users randomly. Bill Clinton put a stop to this in (I think) May 2000. The trouble is that the GPS signal is so weak that it's relatively easy to attenuate and jam the signal. I was told that the signal strength is comparable to trying to see a 20 watt lightbulb from 10,000 miles away!

The US are working on methods of checking that GPS signals are accurate but I'm not sure what checking systems are available for it here in the UK.

I'm sure that most users are aware of the potential inaccuracy of GPS and would never rely on it as a primary navigation aid.

0918

[IO540]

I was told that the signal strength is comparable to trying to see a 20 watt lightbulb from 10,000 miles away!

This is probably true but one could come up with an amazing statistic like this for most forms of radio communication!

GPS can indeed be jammed. There is a very interesting report from the US Volpe Institute (probably there's a link on the www somewhere; I know it is definitely online in their archives) which tells you all about it, how to jam it, and how to make a system less vulnerable to jamming. All this stuff has been in the public domain for many years.

But we come back to the not-subtle difference between using a GPS for sole navigation (which is daft) and using it for primary navigation (which is perfectly acceptable because you have an alternative).

The 99.9% or whatever of the time that GPS works perfectly, it is absolutely worth having. If it goes.... well your cockpit workload goes up considerably but that's about it. The biggest problem with GPS is that we have an army of traditionalists who fear that the moment a PPL gets a GPS he forgets all his map reading skills. True for some no doubt, but true for all??

[Barnaby the Bear]

I was of the understanding that GPS was set up by the US military for missile guidance. The accuracey of it to the civil world was slightly out off alignment.
This has changed now slightly, but it will still be subject to military interference. :}
Maps are still a wonderful thing.............Ok so I'm an ATCO that has had problems in the past with a minority of GA pilots relying on GPS and not looking at maps. :O

[wet wet wet]

To get back to the topic, myself and several of my mates have noticed that there is an area between Birmingham and Oxford where there is often no usable signal. Don't know why. But it's not a legal aid, we don't pay for it, so can't complain!

[S-Works]

I don't see what is wrong in using a GPS as a primary navigation aid. It is very common in the USA.

I always draw my route on a map along with the wind and the radio frequencies that I need on route marked in the places I need to talk to people.

I then fly the course using the the map and GPS and radio nav aids as a back up. If the GPS signal fails (the unit is mains powered 196 with battery backup) then I just carry on with "conventional" navigation.

A stopwatch and ruler are out of the arc, I think pilots should learn about GPS as an aid to navigation as part of the basic PPL. I think GPS in combination with a map would save a lot of controllers the headaches caused by airspace busts and lost pilots. GPS is an excellant aid to situational awareness.

Of course the loss of the GPS signal in this case could be attributed to a broken wire............... :O

[Ludwig]

Bose-x, as indeed it would seem thanks. I tried the unit with an old Garmin 90 aerial and it works again.

As everyone now uses GPS, expect for those who escew the idea of technology, I vote that we have a complete ban on stupid position reports. " G-PS is nine point seven two three miles south of whereever, heading two three six point eight degrees, estimate your overhead in sixteen minutes thirty eight seconds":yuk:

[Flyin'Dutch']

GPS is actually allowed to be used for IFR en route navigation providing your unit is BRNAV approved.

The main difference between those (panel mounted) units and the hand helds is that they have a RAIM warning which basically alerts you that the signal is not useable for navigation (bit like a flag on the VOR indicators)

HTH

FD

[reynoldsno1]

Fact - GPS is approved as a primary means IFR navigation aid for en-route, terminal and non-precision approach aid all over the world (which actaully extends beyond the continental boundaries of Europe;) )
Fact - GPS will never be approved as a primary means VFR navigation aid, but is another useful supplementary aid (as are NDBs,VORs, DMEs etc ....
A hand-held type GPS and an IFR approved receiver are very different animals.
In general, GPS jamming is a bigger problem in Europe than elsewhere due to the overcrowded frequency spectrums - GPS can be affected by harmonics.
The ground navigation aid infrastructure and radar coverage in Europe means that GPS is not as operationally important as in other parts of the blue marble...

[IO540]

Barnaby the Bear

Selective availability (degrading of the GPS signal) is only of the order of 200m which is still highly accurate for en-route navigation.

Bose-x

I agree entirely but it will never happen (GPS in the basic PPL). Can't be done, due to backward attitudes, lack of money to equip planes, lack of time in the 45-hour syllabus... It might happen as an add-on module.

[Barnaby the Bear]

Ludwig,

You mention 'Stupid position' reports. But if you are trying to give a FIS or joining instructions, VRP's etc are extremely useful.

I am not against GPS by any means. So long as it doesn't stop pilots flying VFR, from looking out of the window. And that pilots using GPS are fully aware of ATZ's or danger areas marked on maps but not always clearly marked on some models of GPS.

I am sorry if this has deviated from the original thread.:D

[IO540]

Barnaby the Bear

Most of us have probably deviated from the original thread :O

My question is this: is there a LAW which says a PPL must navigate using visual navigation? He can LEGALLY navigate with any method that works. This includes IFR navigation (any or all of GPS, VOR, DME, ADF or radar vectors).

A PPL who competently navigates using IFR may have difficulty spotting some VRPs. I have certainly found that some VRPs are far from obvious even when you know exactly where they are, or there is a similar looking object/feature a mile or two away!

[Barnaby the Bear]

IO540,

I am just going by my own experience's as an ATCO, and am interested to hear from a pilots point of view.
Its just that on one occassion, a VFR pilot asked by me to report passing a certain VRP,( which keeps them clear of a busy ATZ) had no idea about the VRP and from the response given, had no map to refer to either.
But was on GPS.
This meant alot of R/T for no good reason, on a busy frequency.

That is just one example of quite a few similar occurrences.

Unfortunately I have only limited flying experience, so I don't get to see things from your side of things as much as I would like to.:ok:

[IO540]

B2B

The man you describe was an idiot if he didn't have a chart with him. Whether the presence of a GPS made him less safe is a matter of debate; I am sure that if you raised it in a CAA Safety Seminar you would get the "right" answer :O

But VRPs are often hard to spot; that's a fact. Personally, I fly "VFR" whenever there's a nice view to be had out of the window, but I always navigate fully IFR, and it's a lot easier to do that. I also get the impression that ATC much prefer people knowing where they are relative to navaids.

I've had several cases of ATC (RIS) telling me I am breaching some airspace; I knew I was 1-2 miles outside it (GPS, DME, radar fix etc) and a subsequent phone call to the ATCU revealed that they were telling me I was breaching "just in case I was" because "they get a lot of VFR pilots breaching their zone". One such place reportedly had 30 breaches of their Class A CTA the previous day ...

So perhaps VRPs don't always work when it comes to CAS avoidance.

[Barnaby the Bear]

I do agree with you. VRP's (when locatable) are an aid to help navigation.
Actually quite good GA Safety Sense Leaflet (25). has just made a timely appearence from the CAA. Worth a read if anybody can get a look.

It answers the original question to the thread, and gives guidance for GPS usage.

:ok: