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  #1  
Old 12-01-2022, 11:39 AM
Dozer Dozer is offline
 
Join Date: Oct 2021
Location: Naples, FL
Posts: 25
Default G5 or 3rd GDU 3X?

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?
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  #2  
Old 12-01-2022, 11:57 AM
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jneves jneves is offline
 
Join Date: Aug 2021
Location: Livermore, CA
Posts: 308
Default

From the diagrams I've seen of various configurations, these looks like a solid option as long as the 2nd AHARs in installed.
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N455DM - RV-6A - Bought Flying - 2021
Tip Up Canopy
IO-360-A2B
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  #3  
Old 12-01-2022, 12:08 PM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,997
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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).
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #4  
Old 12-01-2022, 12:12 PM
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Brantel Brantel is offline
 
Join Date: Mar 2006
Location: Newport, TN
Posts: 7,536
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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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Last edited by Brantel : 12-01-2022 at 12:14 PM.
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  #5  
Old 12-01-2022, 12:15 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 8,041
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Quote:
Originally Posted by Walt View Post
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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Last edited by lr172 : 12-01-2022 at 12:39 PM.
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  #6  
Old 12-01-2022, 12:18 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by lr172 View Post
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
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags, MTV-9 prop
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #7  
Old 12-01-2022, 12:33 PM
Avanza Avanza is offline
 
Join Date: Jul 2020
Location: Vastervik Sweden
Posts: 209
Smile 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
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  #8  
Old 12-01-2022, 12:41 PM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
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Quote:
Originally Posted by Walt View Post
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
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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Last edited by lr172 : 12-01-2022 at 12:47 PM.
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  #9  
Old 12-01-2022, 12:55 PM
mburch's Avatar
mburch mburch is offline
 
Join Date: Feb 2005
Location: Oregon
Posts: 1,514
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Quote:
Originally Posted by lr172 View Post
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):

Quote:
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).
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  #10  
Old 12-01-2022, 06:02 PM
Ed_Wischmeyer's Avatar
Ed_Wischmeyer Ed_Wischmeyer is offline
 
Join Date: May 2005
Location: Savannah, GA
Posts: 1,830
Default

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.
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