Dual GPS NAVCOM use

[Controller92]

Quite a few people run dual GPS NAVCOM setups, such as two GTN 650's; a GTN 750 and a GTN 650 and so on. What is the advantage of having two GPS units? What pilot workflow takes advantage of the second navigator? I couldn't find much on google so I'm asking here. 

[Fly Boomer]

5 minutes ago, Controller92 said:

Quite a few people run dual GPS NAVCOM setups, such as two GTN 650's; a GTN 750 and a GTN 650 and so on. What is the advantage of having two GPS units? What pilot workflow takes advantage of the second navigator? I couldn't find much on google so I'm asking here. 

In my mind, nothing so complex.  It simply gives you two NAVs, two COMs, and two GPSs.  If one of those radios goes TU, you have a backup.  You can argue that "that'll never happen" or "I don't need _____" (fill in the blank), but if it did, it would be at least inconvenient.  We have backup vacuum pumps, backup attitude indicators, backup alternators, backup batteries, etc.  Why not a backup radio.

[Controller92]

That does make some sense, but I don't know if it makes $20,000 worth of sense. Especially considering that even though my GI-275 isn't a certified GPS, it will get me home alive all the same. I'm looking into an upgrade to my panel an I was wondering if it would be worth it to do dual GPS or not. Sounds like not really. 

[KSMooniac]

My plane came with a 530 and 430 combo when I bought it 2007.  I did the WAAS upgrade that year to both units, and they continue to meet my needs all these years later.  Redundancy is very comforting, but like you suggest, I'm not sure I would choose two top-shelf boxes in today's world.  In my case, the 430 serves to display extra data fields 99% of the time since I prefer the arc view on the 530 (Nav 1 page) vs. the conventional map, and the GNS boxes are limited in screen resolution and data display options.  Either box can drive my STEC autopilot, so that is nice.  I have separate CDI's for each one as well.

If I were starting from scratch today or updating a very vintage panel, I'd chose a GPS/NAV/COM box first, and then a NAV/COM box for redundancy.  I still have gyros, so I like the bigger screen of the 530 (or 750, 540, etc) but if I had a G3X or Dynon big screen PFD/MFD, a smaller screen GPS would be perfectly fine.  Extra backup is easily provided by an iPad, portable Garmin unit, Garmin watch, etc.  My requirements are redundant COM radios, and two sources of IFR-capable navigation and approach (in two different boxes).  Portables/non-certified are great for when it really hits the fan...  YMMV

[midlifeflyer]

The workflow advantage is loading frequencies for the next things when workflow is low. 

When I flew a few from the Raleigh area to Philadelphia, a few months ago, PHL ATIS and ground were ready to go shortly after takeoff. COMM2 is my SOP weather/ground/monitor radio. It allows me, for example, to get the weather and then monitor the CTAF at my nontowered destination to get a handle on traffic while still talking to Approach. 

[Jerry 5TJ]

2 hours ago, Controller92 said:

What pilot workflow takes advantage of the second navigator?

When VFR the second screen is set to show traffic, or at night terrain.  IFR it is usually displaying weather pages.  Sometimes the second navigator flight plan is loaded with the alternate approach while navigating with the first navigator.  On long XC the second display may show the XM music selections.  

[rbp]

3 hours ago, Controller92 said:

Quite a few people run dual GPS NAVCOM setups, such as two GTN 650's; a GTN 750 and a GTN 650 and so on. What is the advantage of having two GPS units? What pilot workflow takes advantage of the second navigator? I couldn't find much on google so I'm asking here. 

backup. I went for GTN750xi and a GNC355. i wanted to save some buck so i went for 2 IFR GPSs. rather  than 2 VLOCs.

[glbtrottr]

I’ve played this game before with the 530/440 game as well as an MX20. Wonderful for everyone most of all and least for me. Garmin loved the $$$.

For me?
2 navcomms, one ideally being an IFR GPS. Avidyne over a pure touch 650/750. I have a few SL30’s so those work fine for me …but a Non garmin Tx56a works grand.

Redundancy to me equals a GPS NOT powered by the aircraft connected to a brick battery along with an ADSB receiver , and a handheld that’s battery powered also.

Mophie battery bricks connected to ship power are great. You blow an alternator? Plenty of juice to find yourself, and land

Buying a second gps navcom ? Meh. I don’t need to keep up with the joneses.

My 796’s, 696’s or iPads with foreflight work fine along with a nice Icon radio just in case


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[hais]

Isn't a second NAV/COM required for IFR?

[N201MKTurbo]

1 hour ago, hais said:

Isn't a second NAV/COM required for IFR?

No. I’ve flown IFR in a plane with a single navcom. It’s a PITA sometimes. But those days are gone, just follow the magenta line…

[Jim Peace]

I like having dual GPS and triple IRS at work...There must be a way to do this in a Mooney...

[glbtrottr]

I like having dual GPS and triple IRS at work...There must be a way to do this in a Mooney...

I don’t like the IRS at all…


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[Utah20Gflyer]

I went with a Garmin 355 gps/com and a 255 nav/com, that gives me two coms, one gps and one nav. Everything I need  but nothing extra.  An I pad with gps and connected to a ADSB receiver gives me redundancy that is completely separate from the installed avionics and ship power.  

[jlunseth]

I have had a GPS go Tango Uniform when it was the only Nav instrument in the aircraft, so I have two GPS’s now. Redundancy is the main purpose. I have also had the main receiver fail to display a glideslope, so I always set my second GPS to fly the same RNAV or ILS that I have on the main unit. I have a GTN750 as the main and a 430AW as the backup. The backup is a completely independent system, the 430 is connected to a CDI so if the main system fails for some reason I have the backup. Flying an approach in IMC is not a time to have an instrument failure without another instrument to immediately substitute.

Other than redundancy, the second comm is always useful. I use that to get wx. There are some approaches where a VOR radial is used to determine location of a waypoint. I sometimes use it for that, although in today’s environment you can get that info from the main GPS as a waypoint. The GTN750 is very durable in a technical sense, in that I have not ever had it fail completely,  and have not seen some of the mistakes in the unit such as failing to catch a glideslope that sometimes happened in earlier GPSs. Also, I get rare GPS outages that affect one system (the 750) but not the other. 

A have a few functions on the 430 that are helpful when separated from the 750. For example, if I am doing a long descent I will use the vertical descent function in the 430 and it then tracks the descent so I know I am going to make my desired altitude. The 750 has the same capability, but if I do it on the 430 then I don’t have to leave the main nav screen on the 750 that I am actually using.

When I installed the 750 I already had had the 430 for nearly a decade so I just kept it for redundancy and set it up as a separate system. But you are right, had I done a 750/650 system it would have cost quite a bit and not added much if anything except redundancy, and on the redundancy issue I think it is a mistake to wire a second GPS into the same system as the first, which is the way it is usually done. If something causes that system to fail there is a pretty good chance you lose both GPSs, so why?

[rickseeman]

20 hours ago, Controller92 said:

Quite a few people run dual GPS NAVCOM setups, such as two GTN 650's; a GTN 750 and a GTN 650 and so on. What is the advantage of having two GPS units? What pilot workflow takes advantage of the second navigator? I couldn't find much on google so I'm asking here. 

I think you want dual GPS NAV/COM. There should be some bargains out there on 530W/430W takeouts. There are many advantages. I leave the 430 on the nearest screen. If the engine quits I can look down and instantly see which way to turn to the nearest airport.

[donkaye, MCFI]

An analogy: The Coach section of an airplane arrives at the same time as the 1st Class section.  But the flight is a totally different experience.

My 750Xi has the audio panel and transponder interface.  It's so much easier to use than the separate units.  OTOH you lose 4 data fields.  The 650Xi makes up for that and 2 more.  At other times I use it for additional weather and traffic when I'm using the other displays for other things.  Using the Waypoint function I can load ATIS and Ground for destination in a couple of seconds--at the hold short line before I even takeoff from the departure airport.  I have 3 types of weather, XM, ADS-B, and Stormscope.  That means I can have, for example, XM on the TXi, Stormscope on the 750, and ADS-B on the 650 at the same time.  There are so many more  options available.  Add an iPad and an Aera 760 and you have even more.

Garmin has a variety of units to fit everyone's pocketbook.  Each has its advantages and disadvantages.  In the end it's a question of whether you decide to go Coach or 1st Class.

[mhrivnak]

My J had a 530W/430W combo when I bought it. I sold the 430W during a big panel upgrade, and the proceeds paid for a new GNC 255 nav/com.

I didn't find much value in a second GPS navigator, but I definitely want to be able to shoot an ILS if NAV1 fails. So a new modern NAV/COM works great for me as NAV2 and should last a long time. It also integrates with my G3X Touch installation.

I figure if my NAV1 fails, it'll be annoying, but in the worst case I'll get vectors to an ILS and then wait for VFR weather to fly it to my avionics shop.

Paying for database subscriptions on a second GPS is a significant cost to consider along with the equipment itself.

[donkaye, MCFI]

38 minutes ago, mhrivnak said:

Paying for database subscriptions on a second GPS is a significant cost to consider along with the equipment itself.

Not if you have the OnePak.  Additionally, you get 1 handheld subscription for free.

[mhrivnak]

13 minutes ago, donkaye said:

Not if you have the OnePak.  Additionally, you get 1 handheld subscription for free.

It looks like all of the OnePak subscriptions are more expensive than a subscription for a single GPS navigator. Or am I missing something?

[PeteMc]

22 minutes ago, mhrivnak said:

It looks like all of the OnePak subscriptions are more expensive than a subscription for a single GPS navigator. Or am I missing something?

The OnePac is for multiple GPS databases.  In my case my GTN, GNC and GI275 are all covered with the one subscription. 

It would be very expensive to buy three single DB subscriptions to have one for each device.

 

[PeteMc]

43 minutes ago, donkaye said:

Additionally, you get 1 handheld subscription for free.

Actually....   I believe you only get an Upgrade with your DB subscription, but you do not get a Pilot subscription?  Or was that not the "handheld" device you were talking about??

Before I realized that doing an DB update with Pilot was not really the best way, I was sort of miffed that Garmin didn't give you the basic subscription to do the updates.  Still think they should provide a "Pilot Lite" for updating.

 

[donkaye, MCFI]

1 hour ago, PeteMc said:

Actually....   I believe you only get an Upgrade with your DB subscription, but you do not get a Pilot subscription?  Or was that not the "handheld" device you were talking about??

Before I realized that doing an DB update with Pilot was not really the best way, I was sort of miffed that Garmin didn't give you the basic subscription to do the updates.  Still think they should provide a "Pilot Lite" for updating.

 

You do get a full database subscription to a handheld like the 760, and the Premium Upgrade to Garmin Pilot.  The 760 doesn't show, but it is included as part of the handhelds.  I have it for my 760.  The iPad is not considered a handheld.

https://www.garmin.com/en-US/blog/aviation/garmin-onepak-all-your-database-needs-one-simple-solution/

[KSMooniac]

They also pretend like the 496 doesn't exist and won't update it as part of a bundle either.

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[cbarry]

With all of the gizmos available, does anyone still practice partial panel anymore or has it become simply a function of flying off of a full function backup when something “fails?”

[hammdo]

Wait until a DPE on an IFR check ride covers up those (I have dual G5s) - they can be creative… so I still have Airspeed, Altimeter, VSI and TC so partial practice is still viable…

-Don