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  #11  
Old 01-15-2018, 01:04 PM
BobTurner BobTurner is offline
 
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I misspoke in post #4. My EFIS is off during engine start, but my EIS (engine instruments - GRT puts them in a separate box) is on (GRT says this is okay), and a bright red light is also on until there is oil pressure.
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  #12  
Old 01-15-2018, 03:00 PM
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Raymo Raymo is offline
 
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I power on my dual Dynon 1000T EFIS prior to startup. Both screens have backup batteries to deal with low voltage during engine start. Dynon confirms this is no problem for their system (as do other MFGs). I can power one or both screens on without the master but rarely find a need to do so.

The AD-AHRS receive power from the EFIS in this system so, by the time it is booted up, the system is ready to roll.

I have no analog gauges to monitor oil pressure or anything else during engine start. (KIS)
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  #13  
Old 01-15-2018, 03:05 PM
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larrynew larrynew is offline
 
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Quote:
Originally Posted by Raymo View Post
I power on my dual Dynon 1000T EFIS prior to startup. Both screens have backup batteries to deal with low voltage during engine start.
Same and zero problems in 500+ hours. Started with just one screen but went to both after seeing what a non-issue it was.
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  #14  
Old 01-15-2018, 03:09 PM
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N941WR N941WR is offline
 
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While testing, I would power cycle my Dynons in flight and they would align just fine.
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Last edited by N941WR : 01-15-2018 at 07:29 PM.
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  #15  
Old 01-15-2018, 07:18 PM
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RV7A Flyer RV7A Flyer is offline
 
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KISS.

No avionics master switch. Master switch ON provides power to everything (I do have the E-buss architecture a la Aeroelectrics).

I just leave everything on and start the engine (since I need the EMS portion of the EFIS visible, at least). EFIS stays on through the resulting voltage sag, because it has a backup battery. Other devices like GNS430W, etc., will reboot. No big deal. (ETA: if you're worried about it, which you shouldn't be, you can always turn radios and such off with their Power/volume knobs at shutdown, then turn them on after engine start).

Way simpler, fewer failure points, and I get engine monitoring during the start like you should.
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  #16  
Old 01-15-2018, 07:26 PM
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Toobuilder Toobuilder is offline
 
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I start with everything on and taxi when I'm ready. The brownout on start and alignment while I taxi have not made any difference that I can tell.
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  #17  
Old 01-15-2018, 07:58 PM
dutchroll dutchroll is offline
 
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Any modern decent quality EFIS "should" be able to cope with being on during engine start, though some manufacturers seem to be a bit paranoid in this area despite saying everything fully complies with DO-160 etc.

In my case the engine is started with compressed air, so having avionics on during start via the master switch is a no brainer, but even if I had electric start I would do it the same way, as I'm firmly in the camp which believes having engine instrumentation during engine start is highly desirable.

My EFIS also has a lightning fast alignment and GPS acquisition, and will be aligned before I've finished the before start procedures. The latest generation are getting very good in this respect.
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  #18  
Old 01-15-2018, 08:13 PM
F1R F1R is offline
 
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"In my case the engine is started with compressed air," So either you are flying an AIR HOG. or an MP14 ?
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  #19  
Old 01-15-2018, 08:13 PM
moosepileit moosepileit is offline
 
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Does every GRT have 2 power inputs?

My Sport SX200 does and it makes this dead simple.

The diode action is internal to the GRT EFIS. Hook up power pin the normal way and a second battery on a switch to the other power input. The EFIS takes the higher voltage without a brownout/restart. Turn off the small battery after engine start. Same overall as post #7, save for a diode and resistor run to the backup battery from the main bus to charge it while it is normally unused in flight.

By small second battery I mean 12V SLA 800mAh
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Last edited by moosepileit : 01-15-2018 at 08:21 PM.
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  #20  
Old 01-15-2018, 09:33 PM
dutchroll dutchroll is offline
 
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Quote:
Originally Posted by F1R View Post
"In my case the engine is started with compressed air," So either you are flying an AIR HOG. or an MP14 ?
M14P.

All the battery does for start is open a solenoid valve (and powers the ignition coils). Puts a quick end to any "don't start with your avionics on" arguments!
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