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Avionics – Decisions & Planning Installation


Eventually it is time for all those vague plans and dreams over the last few years to be made real … and this means decisions have to be made so that installation can be planned.

We’ve decided to go for an IFR capable RV14, and a Garmin fit had been chosen some time ago when the autopilot Garmin GSA28 Servos were installed.

Here is the list of the proposed equipment:

G3X System
  • G3X System with two 10.6″ GDU 460 Displays
  • GMU 11 Magnetometer
  • GTP 59 Temperature Probe
  • GAP 26 AOA Heated Unregulated Probe
  • GEA 24 engine indication system (EIS)
  • GTN 650Xi or GNC 355 COM 1
  • Trig TY91 VHF 8.33KHz COM 2
  • GMA 245 Audio Panel
Transponder & Conspicuity
  • GTX 45R
  • Air Avionics Air Traffic AT1
  • G5 Electronic Flight Display
  • GAD 29 Navigation Data Adapter – ARINC 429 data interface
  • GAD 27 Electronic Adapter Unit
  • GSB 15 USB Charger
  • GD40 CO Monitor
Electrics – Boxes to fit
  • VPX Pro Electronic CB System
  • TCW BBS-12v-6ah Back Up Battery
  • B&C LR3D Regulator for the B&C 410-H Back Up Alternator

Those of you well versed in all this Garmin equipment will spot surprising items.

Why have a GAD 27 as well as a VPX Pro? Well, here in the UK the powers that be are still uneasy about Flaps/Trim etc being controlled by a relatively unknown Black (Red!)Box, the VPX. So I intend to control these items from the Garmin GAD 27.

And if you have an Air Avionics AT1 to display virtually all traffic here in Europe (ADSB In and FLARM), why not have a GTX35R rather than a GTX45R. The 35R would supply the ADSB out and is cheaper. The 45R will provide a redundant ADSB in, but it also has a UAT 978 MHz receiver. At the moment in Europe we do not have the luxury of this feature, but politics permitting it may emerge in the future.


Tim, my rivet partner, branched out and made some very useful foam boxes to the dimensions of the Avionic components.

In combination with a 3D program mentioned later, these proved invaluable in testing the configurations.


I’m not concerned with the centre stack in much detail yet … the planned boxes will fit fine.

I plan to make a removable tray for the GTX 45R Transponder.


Access Hatches in the Forward Top Skin opened up more fitting options …


…but much easier with this skin not yet attached : )

3D Modelling – FreeCad

Screenshot 2020 10 16 at 14 37 22

I noticed that Vans publish a 3D CAD file of the instrument panel in the RV14 Download section of their web site, and this got me interested. I’ve no background in 3D etc, but an internet search revealed an open source program called FREECAD which I used to open the file.

Garmin also publish G3X 3D Models (.STEP) of the various components, which Freecad can also read.

To learn the program would be a massive learning curve, but a bit of time invested revealed I could manipulate the component positions with a few keystrokes.

And it was relatively easy to make simple shapes representing the components for which there were no existing files, all to very accurate dimensions. It’s an amazing program.

Anyway, it’s not for everyone, but I found it time well spent, and helped me play about with fitting the boxes in the comfort of an armchair! It enabled me to see exactly if attachment bolts were going to cause issues with other boxes on the reverse side of panels, and how the connectors would clear the structure.

When I reached the stage of producing a DXF format file to get my intrument panel lasercut, I found it not intuitive to produce in Freecad. So I ended up using Autodesk Fusion 360, which is available free for non-commercial use at this time. You do need to to pay something to eventually export a DXF file, but a month’s fee is available to get this done.

If I was doing this again, I’d have used Fusion 360 from the outset, avoiding the use of two programs.

16 March 2021

Screenshot 2020 10 16 at 14 40 24

After numerous iterations here are the locations I’ve decided for the boxes.

I tried to think about which boxes connect to which, but all the constraints of the structure meant some leeway was needed.

Also allowing clearance for the canopy was an important issue!

As you can see from the following screenshots FreeCad enables unlimited and exact views of the planned configuration.

Screenshot 2020 10 16 at 14 40 57 Screenshot 2020 10 16 at 14 41 40


It’s possible to hide components to see behind … here I have hidden the Panel Structure.

Based on wise feedback you’ll see in this picture I’ve moved the AT1 from the central position to the outboard face of the F-01456-R
FWD FUSE RIB. This will allow more room for wire looms in the central area.

17 Oct 2020

So I now have what I hope is a considered plan of where to fit the avionics.

I’m now working on making trays & drilling holes to turn it from a 3D Drawing into reality!


2 comments on Avionics – Decisions & Planning Installation
  1. Mike D

    Bit concerned re not much planning re the centre stack as this is where a lot of the wiring connects , not so much the components but the ancillary wiring. Also this is where both L and R PRIMARY WIRING LOOMS route into this space!

  2. Steve

    Thanks Mike … I’ve been concerned about this too. See update above : )

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