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G5 or 3rd GDU 3X?

Dozer

Member
Guys, maybe I don't need G5 if I am going to install three GDU-460 screens?

I can just add another TCW backup battery and a GSU 25C ADAHRS?
Or It doesn't work this way?
 
From the diagrams I've seen of various configurations, these looks like a solid option as long as the 2nd AHARs in installed.
 
IMO, minimum for IFR is 1 GSU25 and a G5.
If you want to add a bit more redundancy, than 2 GSU25's with G5 (or GI275).
 
My understanding is that the G5 was designed from the ground up to be as much of an unique design as possible when compared with the G3X System. This makes it a better choice for a backup where the failure modes that could take out the G3X are different than those that can take out the G5.

Not sure how true that is today with all the additional integration abilities it has been given over the years.

My recently sold airplane has a GSU-73, GSU-25, G5, and a GDL-39-3D.
 
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IMO, minimum for IFR is 1 GSU25 and a G5.
If you want to add a bit more redundancy, than 2 GSU25's with G5 (or GI275).

This my approach also. The G5 will provide ADAHRS data to the G3x if the 25 fails, as long as you have a switch to turn off the 25, so it acts as a 2nd 25.. Not a believer in that Y2K bug stuff killing everything with the same version (that all stems from abbreviated date issues which don't apply here), but do believe in independant systems for redundancy. A hardware problem in the g3x can throw **** on the canbus, taking the whole thing down. Th G3x is an integrated system and therefore various different failure points across different modules in that system can make "the system" fail. The G5 is a separate, independant system with no other dependancies. You can have 10 PFDs and 10 25's, but any contamination of the can bus takes it ALL down. I believe there are numerous HW and SW faults that can put contamination (i.e. bad data, bad checksums, electrical interference, etc.) on the can bus, not to mention wiring issues or electrical anomalies on the ground plane.

Redundant modules in a common "system" is not the same level of protection as two independant "systems." Just like having both an iphone and an Adnroid doesn't protect you from network outages even though they have different operating systems, assuming they are on the same carrier and tower. It is a "system" of components connecting the calling and called parties and a failure anywhere in that chain creates a problem.

Larry
 
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This my approach also. The G5 will provide ADAHRS data to the G3x if the 25 fails, as long as you have a switch to turn off the 25. Not a believer in that Y2K bug stuff, but do believe in independant systems for redundancy. A hardware problem in the g3x can throw **** on the canbus, taken the whole thing down.

The nice thing about 2 GSU's and a G5 is in case of a 'soft fail' you have a tie-breaker. 3 sources are better than 2 :D
 
G5

When used as a backup instrument for your G3X, G3X Touch or other compatible glass display system, G5 provides a full range of supplemental EFIS capabilities. So, if needed, it can be used to maintain the majority of your flight display and autopilot control functions — including the ability to fly coupled GPS approaches. G5 will also provide backup ADAHRS reference to the primary displays. So whatever happens, with a G5 electronic flight instrument in your system, you can count on a wider range of options in virtually any shutdown scenario.

Good Luck
 
The nice thing about 2 GSU's and a G5 is in case of a 'soft fail' you have a tie-breaker. 3 sources are better than 2 :D

agree completely and wasn't suggesting that redundant 25's is a bad idea, just that a 25 and a G5 is better than two 25's. The automatic detection of differing AHARS data is a very powerfull feature and likly alerts you to bad data WAY faster than manually comparing to a G5 after determining the plane is not doing what the PFD says it is and the soiled garments likely to have come from that.

Still hoping that someday Garmin will add SW to compare the G5 data along with the 25's.
 
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Still hoping that someday Garmin will add SW to compare the G5 data along with the 25's.

This has been supported for some time - see section 35.4.23 in the current G3X installation manual (revision AQ):

Miscompare Monitoring (see Figure 35-48)– Selecting ADAHRS + SFD will enable Miscompare (differences in heading, attitude, airspeed, etc.) Monitoring between an SFD (Standby Flight Display, consisting of one or more G5 units) and an ADAHRS LRU (GSU 25 or GSU 73).
 
One advantage of having a G5 is that it has different hardware and software from the other Garmin G3X components. That gives freedom from common mode failures that you might otherwise be wary of.

Here's some trivia... The G5 has the same hardware and software in the experimental and certificated versions. BUT... at installation, the G5 is set to run the software in a different mode, so it is technically true but actually misleading to say that the software is the same.

Tomorrow, I'll take the RV-9A up to flight check the new alternator (another post coming up after I get a full report from the shop), and I'll pull the circuit breaker on the ADHRS which will mean no outside air temp, no AOA, and no magnetometer, but everything else will be there. My expectation is that HSI info will revert to course and that the loss of heading will be a non-event.
 
This has been supported for some time - see section 35.4.23 in the current G3X installation manual (revision AQ):

Thanks for this!! I asked on this forum a year or two ago and G3xpert said that it wouldn't compare to the G5. Hopefully this is available on my non touch setup.
 
When used as a backup to the G3X Touch, the G5 also gives you a convenient baro setting knob. Finding the baro setting on the GDU can take more than one step, but it’s always there on the G5, so I always set the altimeter from the G5 rather than the GDU.

Also, think about where your screens are in your plane. My RV-14 has a G5 on the left, then a 10” PFD, then an avionics stack (just a GTN 650 and GMC 507), and then a 10” MFD on the copilot side. I barely even use the MFD because it’s so far over there. If I have a PFD failure, I think it would be a lot harder to fly from the copilot display than from the G5.

As far as redundancy goes, my PFD has backup RS-232 connections to the GEA 24 and to its GSU 25. My understanding/memory is that the PFD will detect a CAN bus failure and use the engine and ADAHRS data from the RS-232 lines. But even if that fails, the G5 will be there for me.
 
Also, think about where your screens are in your plane. My RV-14 has a G5 on the left, then a 10” PFD, then an avionics stack (just a GTN 650 and GMC 507), and then a 10” MFD on the copilot side. I barely even use the MFD because it’s so far over there.

The way to get more utility from the MFD is to operate the MFD in split screen mode, with the knob-selectable content on the left (inboard) side and the one of three screen choices on the outboard side. This brings the MFD closer, and is how I do it on my RV-9A.

If you look at any of the full screen displays, almost all the information content is in the center half and the outside quarter on each side adds little extra information.

On my installation, the standard setup is:
** On the left screen, left to right: engine instruments, flight instruments, selectable "MFD" information.
** On the right screen, starting from the aircraft center (left side): "MFD", flight instruments, engine instruments

Even if nobody ever flies the plane from the right side, split screen is useful because it brings the highest information content closer.

I had an iPad but sold it for lack of use... my flight plans are almost always GPS direct, so uploading from an iPad has little value.

Garmin has under-sold the usability of the two-screen system, a lot... how sad.
 
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Back to the original question...G5 vs GSU25.
Regardless of how many GDU's you choose the G5 is a better choice for backup ADAHRS.
Reason? Different hardware, different software, self contained 4 hr battery. All of this and fully compatible with G3X system.

G3X can be configured to compare GSU25 and G5 solutions and alert the pilot to discrepancies. As previously stated, you can additionally add more GSU's if you like depending on how much redundancy you want.
.
 
Bucking the trend here... Two GSU 25s and a TCW IBBS battery.
Cost wise it was just slightly more than two 10" displays and a G5.
As far as redundancy goes...we used to fly with a single vacuum pump and unreliable analog instruments (remember tumbling gyros?).
 

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As to the 2 screen vs 3 screen debate.

First we need to differentiate what screen means. Garmin navigators (GTN's, 2" navs) are designed to work both with a full up G3X system and a panel with steam gages. If you don't have another display system (G3X, Dynon, etc) the screen on the navigator is very helpful. If you do have another display, the navigator screen isn't as helpful. A G3X GDU configured as s MFD is much more capable than a GTN 750 screen. Since the GDU can display the same info as the GTN (plus some more) it makes a much more useful tool in the center of the panel. As a plus, a GDU is cheaper to operate. Database's are quite a bit higher for the GTN's than the G3X. All that's required to maintain a legal IFR database is the NAV DATA portion. That is available as a stand alone database at a much lower price than the full up package.

Full package for G3X, NAV DATA only for navigator is the least costly database option. (If using a GTN 700 as a second screen you'll want the full GTN package)

That brings the debate to:
GDU - GTN 700
GDU - GTN 700 - GDU
GDU - GDU + GTN 600 or 2"
GDU - GDU - GDU + GTN 600 or 2"

The second GDU adds a lot of capability over a single one. Two GDU's next to each other (L & Ctr) is much more useful than two GDU's on opposite sides (L & R). A third GDU adds some additional capability but not as much as the second one did. The main advantage is full up capability for a R seat pilot.

Even though multiple GDU's offer reversionary display capability (MFD becomes PFD with PFD failure) a G5 is the best option for redundancy of ADAHRS data.

Now that we've been talking multiplicity and redundancy so much.... Don't forget.... You still have only 1 engine.
 
Backups

How about 3 screens, dual GSU25's, GI275 (just in case) :eek:

i-DG5Wnbc-L.jpg
 
Another option for 3 GDU'S, GTN and a G5.
 

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