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velletazjp
Joined: 08 Oct 2019
Posts: 9
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 Posted: Wed Apr 01, 2026 12:37 am Post subject: Z12 Review for my Experimental Robin DR250 |
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Hello all,
I would greatly appreciate a review of my electrical wiring diagram, and I would be especially grateful for any feedback.
This is a 4-seat, wood & fabric, amateur-built, tailwheel aircraft. It's a clone of the famous Robin DR250.
The primary mission is day VFR, with a strong focus on mountain flying. The aircraft will also be used for cross-country flights, with occasional night VFR and light IFR operations (no icing - no precipitations) (supported by a certified GPS).
The engine is a Lycoming IO-360 (parallel valve) equipped with a Bendix-style mechanical fuel injection system. Ignition is currently provided by dual Slick magnetos, with provisions for a future upgrade to an electronic ignition system (PMAG).
The electrical generation system consists of:
- A PlanePower alternator (12V, 60A – ALY-8520LS) regulated by a B&C LR3E
- Backup alternator: B&C 410H with LS1B standby regulator
The avionics suite is based on Garmin G3X, including:
GAD27, GEA24
Dual-screen setup (PFD + MFD)
2-axis autopilot (GSA 28 servos)
The aircraft is equipped with:
Electric roll trim (Ray Allen T3-12A)
Electric pitch trim (Thomson Linear MD12)
Both trims are controlled through the Garmin autopilot servos.
The electrical distribution is organized around three buses:
MAIN BUS (20 positions)
E-BUS (10 positions)
BATT BUS (6 positions)
All using fuse blocks.
The architecture is based on the Z12 (dual alternator, single battery) design, with minimal modifications:
Replacement of fuselinks with ANL current limiters, as seen in more recent architectures
Replacement of shunt fuselinks with 1A breakers, per Garmin G3X installation manual recommendations
I am also intentionally trying to keep the number of circuit breakers to a strict minimum. At this stage, only two breakers are used, both dedicated to alternator field activation.
You will find the wiring diagram below.
Any comments, critiques, or suggestions are more than welcome.
Thank you very much for your time and expertise.
Best regards,
JP
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DH 251 panel G3X.pdf |
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user9253
Joined: 28 Mar 2008
Posts: 1969
Location: Riley TWP Michigan
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| Posted: Sat Apr 04, 2026 1:21 pm Post subject: Re: Z12 Review for my Experimental Robin DR250 |
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Using one of Bob Nuckolls' diagrams with minimal modifications is a good way to go. You might consider using hall effect sensors instead of shunts.
Amploc has issued an END OF LIFE announcement for their KEY100 Hall Effect Sensor (and several others) effective June 1, 2026.
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wsimpso1
Joined: 04 Nov 2018
Posts: 39
Location: Saline MI
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| Posted: Fri Apr 10, 2026 5:49 am Post subject: Re: Z12 Review for my Experimental Robin DR250 |
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Using Z-12 is a great base.
I question having most of your Garmin suite on th essential bus. When do you need to turn off the main bus? Smoke in the cockpit is a big one. You don't 't know which wire orbox is smoking, so you kill the whole main bus. The more things you put on the Essential Bus, the more likely you are to not shut off the smoking stuff... We usually only want REALLY Essential stuff on the Essential Bus.
Then, after your smoking elements have gone to sleep, if you need something on the main bus, you can shut off everything on the main bus, turn on the Master, smell for smoke, try that item you need, smell for smoke, and get on the ground.
Now comes the nightmare. The smoke was being let out of something you really need. From my quick review, you have two EFIS, so gyro and altimetry functions are still available even if one EFIS is down, but you only have one GPS/NAV/COM. Good reason to have fully charged and engaged EFB and know how to engage it's backup display and Nav functions....
Billski
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wsimpso1
Joined: 04 Nov 2018
Posts: 39
Location: Saline MI
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| Posted: Fri Apr 10, 2026 5:49 am Post subject: Re: Z12 Review for my Experimental Robin DR250 |
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Using Z-12 is a great base.
I question having most of your Garmin suite on th essential bus. When do you need to turn off the main bus? Smoke in the cockpit is a big one. You don't 't know which wire orbox is smoking, so you kill the whole main bus. The more things you put on the Essential Bus, the more likely you are to not shut off the smoking stuff... We usually only want REALLY Essential stuff on the Essential Bus.
Then, after your smoking elements have gone to sleep, if you need something on the main bus, you can shut off everything on the main bus, turn on the Master, smell for smoke, try that item you need, smell for smoke, and get on the ground.
Now comes the nightmare. The smoke was being let out of something you really need. From my quick review, you have two EFIS, so gyro and altimetry functions are still available even if one EFIS is down, but you only have one GPS/NAV/COM. Good reason to have fully charged and engaged EFB and know how to engage it's backup display and Nav functions....
Billski
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