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-   -   GNX 375 Question (https://vansairforce.net/community/showthread.php?t=170141)

Michael Burbidge 03-31-2019 01:47 PM

GNX 375 Question
 
I'm not an IFR rated pilot, but would like to be at some day. So this might be a naive question. Go easy on me.

Does the GNX 375 also require a Nav Radio. I currently only have a COM radio in my airplane. And I'm trying to decide which ADS-B out product to get. The GNX 375 might give me both of those.

Michael-

RV10Pilot 03-31-2019 02:20 PM

To fly IFR you are only required to have the navigation equipment suitable for the route being flown. So with only a IFR certified GPS you will be limited to in route via GPS and GPS approaches. If relying on only one navigation source is wise or safe is another question. What happens if there are issues with the GPS system? How are you going to navigate then?

Mark33 03-31-2019 03:26 PM

Nav radio
 
I?m going through the exact same dilemma on my -7 build. I have two 10.5? G3x screens, a G5, and a GTN 625 WAAS GPS....without the Nav radio. I?m looking into adding the MGL N-16 remote mount Nav radio to compliment my setup. It looks like it?ll integrate with my system pretty easily and be able to be controlled via the G3X touch.

Mark

sailvi767 03-31-2019 05:46 PM

Keep in mind that over 300 VOR?s will be decommissioned by 2025.
G

Canadian_JOY 03-31-2019 05:56 PM

Quote:

Originally Posted by sailvi767 (Post 1335846)
Keep in mind that over 300 VOR?s will be decommissioned by 2025.
G

That second radio is about a LOT more than just VOR navigation. In fact I would say for most of us the VOR receiver in that NAV radio is the lowest priority in terms of functions contained in that box.

When you're stuck in the clag and low on fuel over your destination airport that's suddenly gone to minimums, you're 100% reliant on your GPS to provide approach guidance to get you down through the clouds to the ground. All it takes is one little snafu in the world of GPS (either on-board your aircraft or with the larger space-based system) and suddenly you're in a world of hurt.

That NAV radio gives you the all-important ILS receiver so you can divert to an airport with an ILS (either ILS or localizer non-precision) approach. Without that NAV radio on board you'd better hope you can find an airport that can do a GCA or provide other very precise guidance via radar. Good luck finding one of those when you need it most!

Don't focus on the decommissioning of VORs - if you do, you're losing sight of a major link in the chain of IFR equipment redundancy.

sailvi767 03-31-2019 06:31 PM

The onboard portion of redundancy is easy. There are a variety of low cost GPS units I would be comfortable shooting a emergency approach on like the Garmin 696. The ability to shoot a ILS is great however those are also going to start phasing out. I suspect in 10 years most medium to small GA airports will lose their ILS approaches. As far as I know since GPS was certified for aviation use there has never been a systemwide failure. The chances of the GPS network failing is so low the FAA considers it not a issue.

Turbo69bird 03-31-2019 06:40 PM

Never say never , I have a garmin 300xl and would likely keep it just for ils. Or I have a king radio is a nav com as well.

The nav com is a kx125 which apparently still brings pretty good money. You can also buy the new still on air craft spruce.
https://m.ebay.com/sch/i.html?cmd=SK...kw=king+kx+125

The 300xl is an IFR navigator I thought the 150 and 250 were as well but all the listings I see say VFR.
Couldn’t even find a 300xl for sale anywhere
For reference.

BobTurner 03-31-2019 06:49 PM

Quote:

Originally Posted by sailvi767 (Post 1335866)
. The chances of the GPS network failing is so low the FAA considers it not a issue.

Just 6 months ago I watched an instrument student under the hood shoot the gps approach (vfr) into LVK. First the 650 downgraded from LPV to LNAV, then just before touchdown, displayed a big red X and said ?no gps?. The 650 was working fine. I don?t think the chances are so low at all, although most outages are due to deliberate military jamming tests, or other unauthorized interference. But if it doesn?t work, it doesn?t work.
Something for the OP: While it is legal to operate with gps only, as an instrument student you have another concern: The current practical test standards (I mean ACS) require you to demonstrate 3 different kinds of approaches. GPS can do two. Some examiners will bend the rules, some will not. Something to think about, if you plan to train in your plane.

BobTurner 03-31-2019 06:53 PM

Quote:

Originally Posted by Turbo69bird (Post 1335867)
Never say never , I have a garmin 300xl and would likely keep it just for ils. ]

The 300xl doesn’t have an ILS. It’s a TSO 129 (non-WAAS) GPS certified for non-precision approaches, but only when alternate navigation (e.g., VOR-ILS) is on-board.

Canadian_JOY 03-31-2019 09:21 PM

Quote:

Originally Posted by sailvi767 (Post 1335866)
The onboard portion of redundancy is easy. There are a variety of low cost GPS units I would be comfortable shooting a emergency approach on like the Garmin 696.

Whether we have two or 10 GPS units on board, we do not have redundancy. We are completely reliant on GPS. A search on this forum will reveal several instances where the wonderful Garmin GA35 antenna failed in a manner that turned it into an active on-board GPS jammer that took out every GPS receiver on the airplane. That's just one example of a failure that can take out GPS.

The long and the short of it is that redundancy is best achieved through having multiple disparate systems, not multiples of the same system.

Yeah, ILS is old school - I get that. Still, it's the only on-board precision approach alternative we have to GPS-based approaches. If you're really thinking about the "what if" scenarios we really, really have to look hard at that big question... "What if GPS fails?" Because it DOES fail.


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