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By Keef
#1211884
Nice one, Moose!

Scary if both GPS units can fail. Do they share an aerial? I wouldn't be happy with a setup that did!
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By PeteSpencer
#1211906
Maybe a case For buying a small portable/handheld GPS to keep on your flight bag, fired up and ready to go.

Interesting report: what a good job the weather played ball.

Peter
By lordbonville
#1212087
Or learn to navigate visually by map or in IMC on traditional instruments???
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By Keef
#1212088
Not a lot of traditional navaids where Moose is. One bit of jungle looks very much like another.
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By Rich T
#1212090
lordbonville wrote:Or learn to navigate visually by map or in IMC on traditional instruments???

Erm, did you actually read the article, lordbonville? That's exactly what Moose did. Your sarcastic comment looks a bit daft in that context.
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By Keef
#1212099
I don't think it does on the portables, Leia. Nice, though!
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By Moose
#1212101
In my experience, GPS and DME distances aren't significantly different unless you're very high over a nav aid where the slant angle makes a more significant difference.

The two GPS systems each have their own antennas and IAUs, and provide two totally independent sources of GPS data. To loose both is highly unusual and frustratingly it's been happening ever since, despite numerous swapping out of parts for fault finding. It's giving our engineers a major headache to get to the bottom of. As the aircraft is so new, Pilatus are actually sending someone out here to come look into it as a warranty issue.

I do carry my iPhone and iPad, both of which have basic topographical maps on them from Delorme (as part of their inReach SE tracking unit), so I could easily fire one of those up if the worst came to it. Papua's not a place to be chancing your luck and you really need to be fully aware of where you are at all times, especially when the wx is bad.

I'd read about Garmin's dead reckoning mode in the AFM and Garmin's G950 manual but this was the first time I'd seen it in action. Very impressive and whilst you wouldn't want to be flying IMC with it, it's surprisingly accurate considering I was having to made some rather steep turns/descents to drop between the clouds and valleys to get into my initial destination.

And lordbonville, I'm assuming your comment was in jest but in-case you were being serious I'm perfectly capable of flying with visual reference to the ground thanks; although the VFR maps for this area are rather poor and not much more than topographical charts, so one has to rely on local knowledge more than charts. I'm also quite happy shooting any kind of IFR approach out there (inc. NDBs, although thankfully Indonesia doesn't use these any more).
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By Moose
#1212102
Keef wrote:I don't think it does on the portables, Leia. Nice, though!

I can't see it working on a portable unit as it requires airspeed and heading data to function and calculate your position based on those readings from your last known GPS position. Bloody clever stuff really :)
Last edited by Moose on Thu Oct 10, 2013 12:24 am, edited 1 time in total.
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By GrahamB
#1212139
My GNS430W goes into Dead Reckoning mode if it loses (not looses :) ) all satellite reception, and it has no external airspeed or heading input. It just assumes you will continue with current track and speed.
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By Keef
#1212185
My car one does that in tunnels, where it works reasonably well. I don't think I'd trust it in the air!

Moose's one sounds more like a substitute INS.
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By Howardlong
#1214786
Keef, some of those sat navs work using MEMS accelerometers, and some dashboard integrated sat navs use the car's wheel speeds, some both, in conjunction with a good guess that you're unlikely to be off-road in a tunnel.

On a project I worked on about five years ago we looked at using MEMS accelerometers on an in-orbit payload as a means of attitude determination but their long term accuracy is rubbish. Good enough to figure out how hard you press a key on Garageband on an iPad but not for reasonable determination of heading and speed without other inputs such as known spatial constraints, something you don't have much of in space or in the air for that matter.