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I think a lot about redundancy. In the airplane my redundancy is an IFR GPS backed up by a VFR (portable) GPS. That gives me redundancy against failure of one piece of equipment and also redundancy against an electrical failure. I also have VHF nav capability as redundancy against the failure of GPS as a navigational service. That could be due to military dithering, or a computer glitch at headquarters that takes down the network, or a solar flare. Something external like that.
One time, back in the day before I had a GPS in the panel, I borrowed a Garmin portable from a friend but I forgot to borrow the antenna. So I put the unit in simulator mode and put the “airplane” roughly on my heading at roughly my speed, and the map display was great for situational awareness. So I can attest that the GPS map and database was useful on a night VFR cross country flight, even without being the primary means of navigation.
I suppose I look at VHF nav the way I look at the vacuum system. The “differentness” of it makes for good redundancy.

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I would never consider flying IFR for real in an aircraft that didn’t have at least one radio capable of receiving an ILS signal. I have seen GPS glitches where position data was momentarily lost, and of course there are some sections of the country that frequently have GPS being jammed, sometimes over sizeable areas. I would feel a little more comfortable if the nav receiver could pick up the other competing GPS signals, but I would probably still want some backup capability.

The decision that my flying club is facing is that our #2 nav/comms are aging and will need to be replaced soon, so do we go with another basic nav/comm, or with one of the gps/comm products that Garmin has recently released.

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If you do IFR, still keep one VOR/ILS nav head, just the same as you have at least one backup to your attitude instruments.

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GPS is, we all agree, wonderful. And yet, as an “RF guy”, the thought of the entire world depending solely on a constellation of systems that can be taken out of service over wide areas by a few properly placed jammers, or perhaps a once in 70 years solar event, always struck me as smacking of hopeful thinking.

These dangers can be mitigated, to a degree, through improved receiver design and super-hardened satellites, but at considerable cost. In fact, I suspect that in spite of the (hopeful) assurances of Ligado Networks, if the FCC sticks with their decision to reduce the current de facto guard bands GPS currently enjoys we may get a taste of what intentional jamming could do.

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Gary … the Aera 660 portable can use both GPS and the GLONASS signals … you bring up a very salient point! I assume the new Aera 760 can do the same thing? If you’ve got one certified GPS receiver aboard, I’d sure consider one of those portables for a backup. I’m in love with my Aera 660 and plan to trade up.

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Lots of good gouge here. I’m in this exact conundrum myself as I want to both upgrade and simplify the radios in my C172 used for local area VFR recreational flying 98% of the time. I have an Aera 660 but will trade up for a Aera 760 soon. Along with an iPad running FlyQ, that’s about all I need beyond a comm radio and already installed GTX335 ADS-B out with GDL50 in. That said, I have a brand new King KX125 in a box and could install it but then I’d have to put in a separate intercom and lose some vertical real estate.

I carry a Bad Elf GPS pendant in my flight bag in case my other source of GPS for the iPad goes out. Not discussed here is the fact that if you’re using a panel mounted GPS nav source for IFR, you have to keep up the subscription. That’s another consideration.