GPS fails over Shawbury

[jayemm]

Last friday I routed via Shawbury to get up to Blackpool.

In the Shawbury vicinity, my GPS III began to misread, at one point telling me I had a Ground Speed of about 4356 knots (unlikely in a PA28). I was using it as a secondary aid, so had no problems.

After powering off and reinitialising the GPS, it seemed to recover approaching the Wallasey VOR. I thought nothing of it, and had no further problems to Blackpool and then on to Scotland.

However, on the return journey this Monday, exactly the same thing happened again around Shawbury. The GPS started working again about 20 nm south east of SWB.

Did I miss a NOTAM? Is there something special about Shawbury? Can someone explain this?

[VP959]

Interesting.......... Had it been over Hereford I could understand it. Perhaps some of those chaps were playing up at Shawbury without telling anyone?

[Fly Stimulator]

I landed at Aalborg in northern Denmark a couple of weeks ago. It's a combined military and civilian field, and it has an impressively large radar rotating at ground level not far from the taxiway.

As I taxied past it my Garmin 196 was stunned into silence and had to be powered off and back on once away from the radar before it would come to life again.

I was also getting a distinct 'thump' sound in my noise-cancelling headsets every time the radar rotated past me.

Reminds me of the time I worked on computers in a port-side building. One day they started to go bonkers every few seconds. Took a little while to connect this with the Navy ship which had come to visit and tied up at the nearby wharf with the radar still operating.

[Big Hilly]

Hmmm . . Interesting. . .

I too was up in the Shawbury/Welshpool area a couple of weekends back and my GPS III froze, twice!! Now this is something that it has never done before and I hadn’t given it a second thought, but after reading this. . . .

Best wishes,

BH

[Whirlybird]

Never happened to me, and I use my GPS to find Sleap - inside Shawbury's MATZ - in anything other than perfect vis. Yes, I know it's my home airfield, but it sits in the middle of the somewhat featureless Shropshire plain, and I still have trouble finding it sometimes.

I guess you have to be based in the area for your GPS to work there.

[Big Hilly]

I guess you have to be based in the area for your GPS to work there.

Nah Whirly, it's because your fling-wings repel the rays from the evil device that they're secretly testing on us. . . .

BH

[Whirlybird]

Big Hilly,

It can't be that. I fly a C150 out of Sleap...and it had non-whirly wings the last time I looked. There are no helicopters based there unless you own one...I fly them from Hawarden. Nope, it's a special dispensation for Sleap based aircraft, that's what it is.

[Shaggy Sheep Driver]

And I too am a frequent visitor to the skies around Sleap, Shawbury, Sherlowe, and Shrewsbury. My Pilot 111 has never faltered, though it did so once over the Lake District from Morcambe up to the Solway. And the other pilot in the aeroplane also had a Pilot 111, and his did exactly the same (both units showed 'no signal' just for that leg).

SSD

[Megaton]

Did have GPS fail consistently whilst living in Texas but it was always in the same place....in the vicinity of a certain small town called Crawford! No coincidence, I think.

[maggioneato]

I am based at Sherlowe, just inside the Shawbury MATZ , have never experienced any problem as described with my Pilot111 in the three years I have been flying from there.

[Whipping Boy's SATCO]

I must admit, it was me. I was at home last Friday afternoon and was getting sick of just looking at yellow and black helicopters flying over the top of my house (Peplow airfield 5 nm E of Shawbury). I did a Blue Peter special with a coat hangar and a 12 volt battery and, before you know it, there was all sorts overhead. Didn't do it for long as the incessant noise woke the dog and he started to knaw on my ankle.

Seriously, 4 years flying in N.Shropshire and I've never had a GPS drop out. Malvern, yes; Shawbury, no.

[Reichman]

I flew into Shawbury on Sunday. I wasn't at all surprised to find that my map still had a line and heading drawn on it, my compass still showed the correct heading and my stopwatch still showed the correct elapsed time for that particular leg. Spooky.

Reichman

PS. They all worked when I left Shawbury as well. Amazing!

[IO540]

The only likely reason why a GPS would regularly fail in a particular spot is that the unit is affected by high power radio signals.

This is why the GPS aerial/antenna should always be roof mounted.

The handhelds with integral aerials (e.g. most Garmins) are probably hanging on by a thread most of the time but they do it pretty well so most people are not aware.

If I was using a handheld regularly I would connect it to a roof mounted GPS aerial. Every plane in which a GPS is being used should have one of those fitted, IMHO.

[VP959]

IO540 wrote: "If I was using a handheld regularly I would connect it to a roof mounted GPS aerial. Every plane in which a GPS is being used should have one of those fitted, IMHO."

This could be a bit of a problem if you fly something without a roof..........................

[IO540]

VP959

Indeed, but if you don't have a roof, your GPS reception would be a lot better

[Fly Stimulator]

I wasn't at all surprised to find that my map still had a line and heading drawn on it, my compass still showed the correct heading and my stopwatch still showed the correct elapsed time for that particular leg. Spooky.

Reichman,
You may get away with that sort of complacency now, but if you intend on keeping up flying into old age you could find that the lead in your pencil lets you down. When that day comes, your views on the merits of GPS may change.

[Big Hilly]

I've worked it out!

Have you noticed that it's only the 'regulars' in the area that claim they've never had a problem????

It's because Whirly and Whipping Boy's SATCO (he even admitted as much in the above post) have rigged up an evil device to give us visitors grief. . . I can hear them now, sat there in a field with a pair of binos, a flask of Borders Ale and a laptop with G-INFO installed on it:

"What's the reg"?

"G-XXXX, quick look him up, where's he from"?

"Ah, the South, right Whirly, get out the Pangalacticgargleblaster, let's play with his mind. . . ."

BH

[Whirlybird]

Damn, we've been rumbled.....

[Reichman]

Fly Stimulator,

How did we all navigate around the world before GPS?

I find your attitude to navigation incredible. Are you advocating that GPS navigation should take precedence over map reading skills? I do hope not.

Thanks for the compliment about flying to a ripe old age though. Maybe I already have?

As for running out of lead in my pencil - I carry a spare.

Reichman

[david viewing]

The only likely reason why a GPS would regularly fail in a particular spot is that the unit is affected by high power radio signals.

Not necessarily. Low power signals from inside your own aircraft could also do the trick, perhaps related to the COM frequency or navaid in use at the time, especially if you have a sucker mounted antenna. This would give the appearance of a geographical base to the fault.