That is what DME/DME is for. :)
Do you have DME-DME in your jet FMS, Jason?
I have only my phone and sitting on a ski lift so can’t find past threads on this but there are fibre optic gyro products around the 20k mark, which give you NMEA OUT if the GPS fails. Good for navigation for some hours. Easy enough to rig up to drive a tablet, but AFAIK no panel mounted GPS can take external NMEA unless you use it to create a fake GPS signal.
Yes, it will do DME/DME and DME/VOR.
Having flown 22Hrs VFR through much of the Western US this month I can say with confidence that I don’t leave anything at home because of GPS. I still order paper sectionals and draw lines on them. I still have all the sectionals I’m expecting to need, and a few I don’t, in the aircraft. I still check VOR’s. If the plane had a DME, I’d use that too.
However, My primary navigation is the panel mounted KLN-94, backed up by the wondrous Foreflight on two functioning and two backup iPads. I constantly cross check position with the paper maps, which are easier to read in terms of identifying ground features and mountain ranges since they equate to a 48" hi-def screen. And the wonderful US sectional fan-folds in flight like a dream, unlike certain ghastly European maps. So do I rely on the Magenta line? Certainly flights would be less pleasurable without it, but since I constantly know where I am on the paper maps then temporarily losing GPS would not be a disaster. And after all, before the inception of GPS I still made these long cross countries, often the biggest issue being identifying which of two similar looking airports was the actual destination at the end of a long flight.
It should be kept in mind that GPS in the US would not vanish without warning. As mentioned elsewhere, ATC are likely to warn of an outage and the standard briefing from the marvellous 1-800-wx-brief, which I use to file FPL for every cross country, always discusses GPS outages. Admittedly a pilot flying without a briefing and without flight following could get caught out and I think I’m in the minority having the paper sectionals in the aircraft. But FF mapping still works without GPS, believe it or not!
But would I still launch on long distance flights if GPS was permanently down? Well, I did in the old days, and never once got caught out. But those flights were definitely less relaxed than today’s, with constant daggers of doubt stabbing at every loss of certainty about position. I remember crossing the Canyon in one of the narrow corridors and not being able to get the VOR cross cuts to agree whatever I did. Fortunately In most of Arizona you can fly without any map at all, just by recognising the mountain ranges, and that’s an equally valid fall-back today.
All these comments relate to long distance VFR, not IFR, of course. Would the same no-GPS scenario work in UK? In the absence of Flight following, joined up ATC and comprehensible airspace I would say the chances of falling foul of the ‘authorities’ makes it a dicey game for anyone planning to make a long term commitment to VFR private flying here. And then there’s the weather…
The VFR/IFR point is very valid; apart from approaches, if you’re really in trouble while IFR, you can ask for a heading. VFR in complicated airspace, on the other hand… Of course it’s perfectly doable, we’ve all done that for our PPL; but it’s a different thing after years of relying on the magenta line, especially if it was unexpected (e.g. if Russia wants to try its toys).
I think your best option would be to call up ATC and tell them you have lost navigation. Better than busting cas. You will get zero credit just because GPS was down.
Peter wrote:
I think your best option would be to call up ATC and tell them you have lost navigation. Better than busting cas. You will get zero credit just because GPS was down.
In the UK, Peter? I wonder how many pilots would do that… (I remember a cringe worthy episode when my former flying partner called up D&D for a practice pan. “Whaddya want?” they said. It was all rather embarrassing and not at all encouraging if you had to do it for real).
Peter wrote:
You will get zero credit just because GPS was down.
What evidence do you have for that?
The treatment I got recently 
Here, a bust is a bust. Short of being on fire…
I am not sure if d&d is actually the best option. But IIRC if you call London Info they have to pretend they cannot see you on radar, and hand you over to someone who officially can, including possibly d&d.
But seriously if I thought this was a likely problem I would spend the 20k. If I did another bust, I reckon a brain transplant under CAA supervision would be the only option on offer
Peter wrote:
The treatment I got recently
You were involved in an airspace infringement at a time when the GPS system was unreliable and that wasn’t taken into account? I am very surprised, from what I know, and have witnessed, of the system at work.
Please eMail me if you would like me to investigate further.
