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  #1  
Old 08-04-2017, 04:45 PM
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rvanstory rvanstory is offline
 
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Default Avionics Advice

Beginning the design for avionics to eventually go into my 10. I already know I'm going all Garmin. I can save a pretty good chunck of change (about $4k) by going with GTN625 with 2 comm radios VS a GTN650 with a 2nd comm. I do fly IMC at times, but haven't done an ILS approach in years. I always request GPS/RNAV approaches. The GTN625 does not have VOR/LOC/ILS capabilities, only GPS.

I'm seriously considering the GTN625 route for cost savings. Looking for others advice on whether this would be ok, or if there's a problem being 100% GPS I'm not giving enough thought to?
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  #2  
Old 08-04-2017, 05:11 PM
BobTurner BobTurner is offline
 
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Certainly people are going the GPS-only route. There are still some places and wx where an ILS will get you there and a GPS won't, but it's getting more and more rare. Questions to ask yourself: what will I do if that one box quits (this question is valid for either of your scenarios)? What will I do if the government is doing tests that block GPS signals? Finally, I have not read up yet on the newly released ACS-instrument standards that replaced the older PTS, but under the PTS there was an issue (but not impossible, IMHO) taking an IPC in an airplane with only GPS - if that's an issue for you.
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  #3  
Old 08-04-2017, 05:13 PM
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bkervaski bkervaski is offline
 
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That's exactly what I did. Dual comms + GTN 625 at the 50% discount when purchasing with the G3X system.

I love flying VORs *for fun* but when it comes to actually navigating in the Cherokee I'm currently flying while I build I just use the GPS in the plane or whip out ForeFlight.

In your 14 you'll have two both G3X that can be GPS sources and then the GTN 625 as your certified GPS source, good to go! You'll probably have your phone so if ALL 3 DEVICES fail, whip out ForeFlight or the Garmin app, etc.

Disclaimer: Not an IFR pilot .. yet
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Last edited by bkervaski : 08-04-2017 at 05:22 PM.
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  #4  
Old 08-04-2017, 05:53 PM
Canadian_JOY Canadian_JOY is offline
 
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Ummm... I hate to be the skunk at the garden party, but here goes.

I'm firmly in the camp of "the more GPS devices the better" so please don't take me as a GPS hater. A good search here on VAF will show multiple instances where well-equipped aircraft with multiple GPS receivers (pick a type, any type) were unable to produce useable navigation guidance. If all you have to navigate by is GPS then you are deep in "sole source" territory.

What causes a GPS "outage"? Well, we know the US military plays war games and NOTAMs broad swaths of the country as not having reliable GPS signals. We've also seen discussed on this forum instances where the Garmin GA35 GPS antenna has become a jammer, wiping out every GPS receiver on the airplane. Recently I've seen several references to SPOT trackers likewise acting as GPS jammers.

While it's great to have multiple GPS receivers, I personally would not want to be 100% reliant on GPS, particularly for IFR navigation. I've gone with a GRT-based panel and recently upgraded my AHARS to the Adaptive AHARS with built-in multi-constellation GNSS receiver. With this device at least I have access to other satellite networks beyond GPS. I've also got an SL-30 to provide VOR/ILS/COMM capability in addition to a GNS480 with GPS/VOR/ILS/COMM. It would be an extremely low odds situation that would cause all of these disparate systems to fail at the same time.

While the pricing on the GTN625 is pretty fantastic, and you're already considering a second COMM radio, perhaps it's worthwhile to consider making that second radio a NAV/COMM. Our European friends are being forced to remove perfectly good NAV/COMM radios to install new radios compliant with the 8.33KHz channel spacing requirement. A sharp shopper could end up with a 625 plus a good NAV/COMM for something less than the extra $4K Garmin wants for the GTN 650.
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  #5  
Old 08-04-2017, 05:55 PM
pilot2512 pilot2512 is offline
 
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I was going your same route until I got a good deal on a SL-30. That gives me a com/nav/ils and my audio panel already had marker beacon. I also figured with an in panel com if I lose my G3X and can't tune the GTR20, i can still tune the SL-30 manually. The deal Garmin gives on the GTN 625 is too good to pass up.

Jay
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  #6  
Old 08-04-2017, 06:08 PM
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bkervaski bkervaski is offline
 
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Quote:
What causes a GPS "outage"? Well, we know the US military plays war games and NOTAMs broad swaths of the country as not having reliable GPS signals. We've also seen discussed on this forum instances where the Garmin GA35 GPS antenna has become a jammer, wiping out every GPS receiver on the airplane. Recently I've seen several references to SPOT trackers likewise acting as GPS jammers.
Yikes! I'm using dual GA-35's .. one for the G3X and one for the GTN-625. Is this one of those things that happens all time time or happened once and made headlines somewhere?
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  #7  
Old 08-04-2017, 06:33 PM
Canadian_JOY Canadian_JOY is offline
 
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It has happened multiple times - do a search here and you'll find several instances.

Garmin's Trek Lawlor provided information here which indicated the GA35 failures were the result of over-torqued mounting hardware. While I do not wish to discredit this explanation nor the person who provided it, I've personally seen one GA35 mounted inside a composite aircraft using Velcro which exhibited the same failure mode, so I'm not entirely sure all the failure causes are completely known.

Let's just say that, at a minimum, one should adhere VERY closely to the torque spec provided by Garmin for the antenna mounting hardware.

And be prepared in case something as unlikely as failure of a component in the antenna, or interference from other devices, wipes your GPS signal off the air. After all, the GPS signal is teeny tiny and it takes very little to jam it. A recent post on this forum hinted that Garmin reps referred to SPOT trackers as GPS jammers so this phenomenon, while not common, certainly isn't completely unheard of. With my luck such a thing would happen on the proverbial dark and stormy night, hence my use of disparate navigation technologies in my own aircraft.
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  #8  
Old 08-04-2017, 11:38 PM
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donaziza donaziza is offline
 
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Quote:
Originally Posted by rvanstory View Post
Beginning the design for avionics to eventually go into my 10. I already know I'm going all Garmin. I can save a pretty good chunck of change (about $4k) by going with GTN625 with 2 comm radios VS a GTN650 with a 2nd comm. I do fly IMC at times, but haven't done an ILS approach in years. I always request GPS/RNAV approaches. The GTN625 does not have VOR/LOC/ILS capabilities, only GPS.

I'm seriously considering the GTN625 route for cost savings. Looking for others advice on whether this would be ok, or if there's a problem being 100% GPS I'm not giving enough thought to?

Randy, if you're serious about a 625, I've got one, brand spankin new, never used. I did open the box just to look and go O-o, Ah, but that's it. $6400 smackers. Don't know where New brunfels is, but if you're within about a 1000 mile radius of Atlanta, and I can get 2 VFR days, I'll fly it to you.

I was going to make my 8 IFR, but I'm getting too old. Wouldn't get my monies worth anymore.

email or PM me if you're interested.
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  #9  
Old 08-05-2017, 04:52 AM
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Auburntsts Auburntsts is offline
 
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I always shudder a bit when someone posts about trying to save money when building an IFR panel. But that's just my opinion and I'm not the IFR panel police. I personally prefer redundancy when flying IFR and the few extra bucks to have VOR/LOC/GS capability is well worth it IMO. Here's a example of why:

https://www.faasafety.gov/files/noti...t_Advisory.pdf

I flew back and forth from Virginia to Florida during this test period and although I didn't experience any outages I did plan for it by filing airways (vs Direct like I normally do) and had the VORs dialed in for all legs and was prepared to shoot non-GPS based approaches.

Like the man said, ya pays your money and takes yer chances.
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  #10  
Old 08-05-2017, 06:21 AM
Dan B Dan B is offline
 
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My airplane is equipped with dual GNC-420Ws (no ILS or VOR). For the last 6 1/2 years, I most often file IFR. 99% of the runways I land on have an RNAV approach, but no ILS. I have encountered GPS interference testing from White Sands at higher altitudes. First thing ATC did when I reported the interference was put me on a vector. RADAR is always a viable backup to loss of a nav system. I have yet to encounter a need for ILS or VOR capability in my airplane.
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