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  #1  
Old 09-27-2022, 07:17 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,620
Default G5 power source question

I have an RV-4 I built with all steam gauges, and recently, I took the leap to a G5 for my primary centered instrument but retained all my other steam stuff for now. I never had a AF Horizon, and now the G5 has me all set. Since the G5 is often used as a back-up, power source seems to be best coming from the main bus the way I see it, and in the event my AVX (com,xpndr,ect) becomes a smoke generator, I want them off-line(AVX bus). Being all that said, I have the G5 wired to the aircraft master side of power, which means the G5 comes alive with the master prior to start of the engine, and I am curious if anyone has had issues that would damage the G5 due to voltage drop and drain during engine crank? I really don't want to physically turn on/off the G5 with every flight cycle. The install manual isn't very clear on preferred/recommended or precautionary choices. How are others wiring theirs?
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RV-4/N76WE
8A7 / Advance NC
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  #2  
Old 09-27-2022, 07:24 AM
dstates dstates is offline
 
Join Date: Sep 2017
Location: Geneseo, IL
Posts: 55
Default

I have dual G5's in my Cessna 170. The attitude indicator G5 is on the master bus and it comes on before engine start and the HSI G5 is on the avionics bus and is not on during engine start. No issues so far (about 2 years).
Both have a backup battery.

Doug
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Doug S.
RV-14 In Process
Wing Kit Delivered 9/28/22
Tail Kit Delivered 10/31/22
Currently flying N1235D - Cessna 170A

Last edited by dstates : 09-27-2022 at 07:46 AM.
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  #3  
Old 09-27-2022, 07:32 AM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 888
Default possible option if needed?

Wouldn't a TCW back-up battery or a dedicated G5 back-up battery be an appropriate consideration if brown out is a concern?
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  #4  
Old 09-27-2022, 07:36 AM
Southern Pete Southern Pete is offline
 
Join Date: Jul 2015
Location: England
Posts: 210
Default

Does the G5 have a battery? If not you may find one useful. It will keep the G5 alive during cranking and if all the magic electric smoke ever escapes. If no battery then the G5 will probably reboot during engine start, it is unlikely to be damaged. I wired mine to come on with the master but I have a battery.
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  #5  
Old 09-27-2022, 08:21 AM
fixnflyguy fixnflyguy is offline
 
Join Date: Jan 2006
Location: Winston-Salem, N.C.
Posts: 1,620
Default I have the back-up battery

Mine has the back-up battery..my only concern is spiking or voltage fluctuation during start-up, and it seems others have wired like mine without any issues. I don't want to fry my new piece of equipment and hear the "I told you so"..Thanks for all the replies from real life experience.
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  #6  
Old 09-27-2022, 09:04 AM
Steve Steve is offline
 
Join Date: Jan 2005
Location: Roy, Utah
Posts: 1,282
Default

I wired my G5 as follows:
Main aircraft power to G5 pin 7 - Aircraft Power 1
TCW backup battery to G5 pin 8 - Aircraft Power 2
I already had the TCW battery installed as part of my G3X system so I did not use the dedicated G5 backup battery.
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  #7  
Old 09-27-2022, 09:28 AM
MacCool's Avatar
MacCool MacCool is offline
 
Join Date: Aug 2020
Location: central Minnesota
Posts: 1,333
Default

Quote:
Originally Posted by fixnflyguy View Post
Mine has the back-up battery..my only concern is spiking or voltage fluctuation during start-up, and it seems others have wired like mine without any issues. I don't want to fry my new piece of equipment and hear the "I told you so"..Thanks for all the replies from real life experience.
I don't think that modern avionics are at risk for those kind of voltage drops on startup anymore. I have an avionics master switch, but it's generally on during engine start...and in two years, no issue. My other avionics, including my Advanced Flight EFIS's and my IFD440 likewise are on during engine start, as recommended in the manual.
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IO-320D1A (factory new), C/S
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IFR equipped
AFS 5400/3500, G5, IFD440 navigator,
bunch of other stuff

Last edited by MacCool : 09-27-2022 at 09:31 AM.
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  #8  
Old 09-27-2022, 09:59 AM
Desert Rat Desert Rat is offline
 
Join Date: Aug 2018
Location: Wichita KS
Posts: 1,048
Default

I just went through all this with the design of my all Garmin all glass panel.

Levi Self who owns Midwest Avionics in Lees Summit Missouri designed everything and fabricated the avionics wire bundles. Levi teaches the AEA course that G3xpert is promoting in another thread right now. He's also a former Garmin engineer.

Based on all that I trust his opinion, and when it came to the discussion of needing an avionics master, his opinion was that I didn't need one. I have a backup avionics battery for the PFD and engine stuff, which will prevent a potential brownnout condition during start, but the G5 just comes on with the master and isn't hooked up to any sort of redundant power supply other than it's own backup battery. FYI- if you don't have a backup battery, the garmin boxes have a pinout that also allows for brownout protection during start via a different wiring scheme.

I questioned this in detail due to 30 years of flying airplanes with an avionics master, but he was confident that with modern Garmin avionics, there is no potential of harming them during startup.

I'm a few months from putting this to the test, so time will tell.
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  #9  
Old 09-27-2022, 10:09 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,443
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There are no voltage spikes during engine start. However, there are voltage sags. Transistors made in the 1960s were vulnerable to voltage sags. Thus the warning to shut off avionics during engine start. That warning has been passed along from generation to generation and persists even today. Transistors were improved in the 1970s. They are no longer vulnerable to voltage sags. However, a voltage sag will cause avionics to reboot. I do not have an avionics switch in my RV-12. The radio and transponder and GPS and D-180 have always been on during engine start for the past 12 years and hundreds of hours. Bottom line: Modern avionics will not be damaged if left on during engine start.
-
P.S. I have flown over 300 Young Eagles, so there are an extra 300 engine starts with the avionics turned on.
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Last edited by Mich48041 : 09-27-2022 at 11:04 AM. Reason: Added sentence
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  #10  
Old 10-01-2022, 08:04 PM
Chipper G Chipper G is offline
 
Join Date: May 2020
Location: Savannah GA
Posts: 97
Default

Install the back up g5 battery and donít worry about it. The g5 manual ref this
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