GPS Malfunctions

[Sgtfrog]

We may have covered this before….
Routing Newbury Racecourse to Bagshot Mast eastbound. Turned north to avoid area R101 and GPS goes to start page!:eek:


This has happened twice in the same place and always on the eastbound leg never westbound using same course. GPS is normally very reliable .


Anybody else or is it just me!:E



Cheers,

SF

[Wizzard]

Sorry, can't help but while we're on the subject; why does my GPS fail every time I go to Gamston? Has done so over the last 10 years!

Wiz:confused:

[Ioan]

I've had GPS return to start page a couple times around Sennybridge in mid Wales - GPS jamming, though it's always been NOTAMed.
Interestingly once it also suddenly changed to show my position as in the south atlantic just off Ghana - 0 deg N/S, 0 deg E/W :eek:

[Billywizz]

It's really spooky but my charts have never failed in any of those places!:)

[Three Blades]

I am afraid that I cannot remember where I saw the details but aparently some radio frequencies can cause a problem with some GPS. Hence if you are east or west bound may mean that you have a different radio frequency set (even on stanby).
More likely to be a problem with hand-held / portable units then the plumbed in versions.

[Sgtfrog]

Quote: It's really spooky but my charts have never failed in any of those places!

Fair one!:E

Three Blades -

Had Farnborough in the active and Redhill on standby - same on both legs, only using box one and the GPS is plumbed in version.
SF

[helimutt]

Routing Yorkshire to Manston in a jetbox once I remember according to gps, being in Leicester for quite a long time even though there was an airport below me that looked suspiciously like Cambridge. I don't 'rely' on gps too much onshore but use it as an 'aid' to navigation. Now I do the sensible thing and use RNAV box of tricks!! :)

[NickLappos]

Lots of failures - any RAIM or other warning lights?

[Sgtfrog]

Nick,
not that I saw - just went off map page and onto start up page - only strange thing is where it happed, twice!

SF

[rans6andrew]

I fly from Brimpton which is in the northern edge of R101. I have a Skymap II and a Garmin 12XL (used handheld on its own battery and internal antenna) and have never had an outage on either of them in the 4 years I have carried them. I depart and return to the field always to the north side of the runway centre line. I don't know anyone else who has had an issue in the vicinity. If anyone from the field had suffered from GPS issues there it would have been talked about in the clubroom.

I do find that my radio doesn't like to receive the airfield transmissions from near to the Kingsclere mast (even though I can see the airfield) but I can still listen to traffic in the circuit at Sandown from there. Strange.

[Sgtfrog]

Must be me then!;)
SF

[Lutefisk989]

aparently some radio frequencies can cause a problem with some GPS.

True...from AC20-138:

Evaluate the following VHF frequencies (25 kHz channels):

121.150 MHz 131.250 MHz
121.175 MHz 131.275 MHz
121.200 MHz 131.300 MHz

For VHF radios with 8.33 kHz channel spacing, evaluate the following VHF frequencies:
121.185 MHz 130.285 MHz
121.190 MHz 131.290 MHz

For installations on rotorcraft, ensure that the rotorblades do not interfere with the GPS/WAAS received signals. This problem has been experienced in some rotorcraft and varies with the rotation rate.

[Shawn Coyle]

The following suggested action may throw the CAA into a bit of tizzy, but it's the only way to start getting their attention.
In the US or Canada, you would file a Service Difficulty Report, detailing time and place, make and model of GPS, etc.
It's a piece of aviation equipment that failed and had the potential to display hazardously misleading information (if you were IFR, it would meet this criteria).
I'd also send a copy of SDR to the GPS manufacturer and note on the letter that you are also sending a copy to the CAA.
This might get someone's attention who can do something about it!

[NickLappos]

sgtfrog,
Sounds like a power reset in your case, where the ship's power to the unit fails momentarily, setting you back to start.

The "typical" gps problem is certainly not anything where the satellite reaches into your set and changes its pages, since they simply can't do that. Such failures are surely inside the receiver itself (a likely place, where mechanical switches abound, and vibration setting them off is a common failure mode.

Typical failures are where the satellites are in odd corners and the nav solution stinks - usually flaged by raim or by a poor signal or poor nav flag.

Signs of jamming are usually where the system cannot lock on the satellites and dumps its nav solution (spoofing a GPS to "shift" the solution is so difficult, it is automatically awarded a PHD in EE).

Here is an example of an inadvertant jammer - its effects and cause.

http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=43404

Let each one with a problem identify the model/make and also if the system was certified on installation by the FAA/CAA/KGB :E

[Ioan]

COM : FROM 04/03/08 08:00 TO 04/03/14 16:00 B0391/04
D)JAMMER A: MAR 08-14 0800-1600
JAMMER B: MAR 09, 10, 11 2200-2245
E)GPS JAMMING EXERCISES.
GPS SIGNALS (1227.60MHZ AND 1576.42MHZ) WILL BE JAMMED DURING PERIODS
STATED ABOVE, GROUND BASED JAMMERS WILL BE LOCATED WI 3KM OF 5201N
00336W (SENNYBRIDGE DANGER AREA).
JAMMER A: OMNI DIRECTIONAL AFFECTING ACFT WI RAD 68NM (DEPENDING ON
ALTITUDE)
JAMMER B: DIRECTIONAL AFFECTING ACFT AT A DISTANCE OF UP TO 210NM IN
THE SECTOR 180 THROUGH TO 240 DEG (DEPENDING ON ALTITUDE).
THE EMERGENCY CEASE JAM POINTS OF CONTACT ARE:
EXERCISE OPERATIONS 01874-635599
TRIALS MANAGER 07813-592626
DURING THESE PERIODS, GPS RECEIVERS MAY SUFFER INTERMITTENT OR TOTAL
FAILURE, OR GIVE INCORRECT POSITION INFORMATION. CREWS SHOULD BE
AWARE OF THESE LIMITATIONS AND USE ALTERNATIVE MEANS OF NAVIGATION.
THE POLICY FOR THE USE OF GPS FOR U.K. AIR NAVIGATION SEVICES IS
GIVEN IN AIC 93/2002 (PINK 41)

one example that's already been posted on PPRuNe

[NickLappos]

The jamming will continue until 04/03/14 That means Barak Obama will be in his second term before you can use your GPS, guys!

[malabo]

I guess that means that everyone's EGPWS wouldn't be working in that area either, so no commercial carriers can be there (MEL item). Same with 406 GPS coded ELT's, all financial institutions would be shut down (they use the US Military GPS time stamp on all financial transactions), etc.

So probably a pretty isolated part of the world.

All GPS problems I've seen for the last ten years are related to GPS units themselves. Commercial operators, especially large ones like Bristow and CHC, are notorious for keeping absolute junk installed in their aircraft long after the "expired" date. Pilots are then forced to carry personal quality handhelds, like the Garmin 296. I've never seen those fail.

Interesting that the UK so thoroughly discounts the value of GPS for air navigation, yet feels obliged to be putting energy in figuring out how to jam it.

malabo

[[email protected]]

Yes, a bit of a typo with that NoTAM in the first line - fortunately the rest of the text is clearer.

[Ioan]

Sorry I should have made it clearer, for lack of a relevant NOTAM handy I searched for this one which I remember having seen posted on here before. Just copy pasted it in, the date format is 8 Mar 04 to 14 Mar 04 so not a typo.
I live only a few miles from Sennybridge and yes it is a fairly rural area. However as was pointed out these do have a fairly large impact; for example aside from aviation (where I've only experienced a signal loss while VFR where it's fairly insignificant) the Brecon Beacons are nearby and climbing around the area I've come across a few puzzled hillwalkers who've got annoyed with their 'broken' eTrexs.
It's just a suggestion why there might be a signal loss in one particular area. In probably 7 or 8 years using a GPS both outdoors and in aviation it's the only time I've seen one fail

[md 600 driver]

i recieved this earlier today from ofcom


The MoD has informed Ofcom of the following GPS jamming exercises:

Dates: 31 March to 4 April 2008
Times: between 08:00 and 18:00 hrs
Location: To sea from Bridlington - N54° 06.842’ W000° 05.045’
Contact: Trial Manager - 07766 134758


Dates: 20-21 April 2008 (26 April 2008 reserve day)
Times: between 09:00 and 17:00 hrs
Location: To sea from The Hebrides - N57° 14.4’ W007° 26.7’
Contact (during jamming exercise only) 07766 134520