Chapter 22 – Instrument Panel Evolution

Chapter 22 – Instrument Panel Evolution

This page covers the multi-year design evolution of my instrument panel.

22 December 2012 — Instrument Panel

Ok, since before I left Germany I have been working on my electrical system design.  I’ve read & re-read Bob Nuckolls’ book, The AeroElectric Connection, which I think most homebuilders would agree–even if they don’t use his designs–that it’s the homebuilder’s electrical Bible.

Of course much of my electrical system design is wrapped up in the instrument panel components: how much current does each component draw?  what’s my fault tolerance and mission profile?  In short, what do I need, and how many of ’em do I need to feel comfortable?  The design and warm fuzzy factor is of course different for each builder.

I spent a good few weeks researching all the options that I saw as viable solutions for my Primary EFIS, a back-up EFIS, an engine management system, back-up instruments, radios, etc.  Basically anything that would go on my instrument panel.  I built a big matrix and essentially had a run-off of just about every system out there.  I also talked to a myriad of people about their take on panel designs.  I called, e-mailed and pestered just about every vendor out there for information.  I looked at a lot of company’s stuff, and here’s a list of the main ones I focused on:

• Dynon
• G3X
• TruTrak
• TCW (back-up battery system)

I may have looked at some others, but the list above was the main jist of my focus.  In my matrix, I really focused on requirements, or in other words “needs” vs. “wants.”  I also looked at current draw, weight, size, ease of use, capabilities, features, interoperability, scalability, cost, etc.  It made me take a hard look at what I thought I was going to put in, and what I COULD put in.  In the end, if you look at the initial pics I took in my project preparation, you’ll see it looks a whole lot different than the latest thoughts I have on the panel design.  I say “thoughts,” because I still have a fair amount of time before I have to buy any panel components, and technology is always changing.  So here’s the latest generic version of my panel:

Chap 22 - Instrument Panel Mock-up

As you can see, the end result of my run off and what spit out of my matrix was Grand Rapid Technologies new 10.4 inch HXr EFIS.  The “r” on the end of HX stands for remote.  It allows almost every traditional panel component: radios, transponder, audio panel, etc. to be placed behind the panel and tied into & controlled by the EFIS.  Another 2 capabilities that factored into my decision was the GRT’s Altitude-Heading-Reference-System (AHRS) box with it’s not requiring GPS input to function as designed… And GRT’s engine management system is rock solid and is the same one used in countless homebuilts.  It’s the same engine management system box, it just gets tied into the EFIS (also remotely) where it displays data graphically.

In addition, a couple of bells and whistles admittedly helped win me over as well.  I really like GRT’s HITS (Highway in the Sky) feature on their EFIS where you essentially fly through the boxes to get the plane on the ground, and their focus on IFR operations.  Finally, GRT seems to play a lot nicer with other vendors out there, so they work with a lot more 3rd party market stuff (GPS, ADS-B, Radios, etc.).

Btw, the instrument panel is covered in Chapter 22 of the plans, which is the Electrical Section.


10 June 2013 — After cleaning up a little bit in the garage, I then went inside the house & spent an hour or so mocking up my instrument panel & figuring out some of my avionics, etc.

Chap 22 - Instrument panel mockupChap 22 - Instrument panel mockup


29 January 2014 — Over the past few months I’ve been going round and round on my Instrument Panel layout. I’ve researched a myriad of instruments & avionics, built matrices to compare various components–from clocks to autopilots–and am slowly getting a picture of WHAT components are going on the panel, maybe just not exactly WHERE the components will go on the panel.  Of course, since I’ve been working on my electrical system, current draw, integration, weight and cost have all been factors in the panel plan as well.

Moreover, a  lot of the panel layout will be based on ergonomics, which of course requires me actually sitting in the cockpit making airplane noises before I decide on my final configuration.

Still, I thought I would post a few pics (out of MANY) of my proposed panel options.

Chapter 22 - Instrument Panel LayoutChapter 22 - Instrument Panel LayoutChapter 22 - Instrument Panel LayoutChapter 22 - Instrument Panel Layout

Again, my panel is currently an ever-changing storyboard.  For the most part, the avionics and instruments are what I’m planning to go with presently, but as time moves on & new technologies and/or opportunities (e.g. the TruTrak ADI) present themselves the panel design can of course easily be updated.

Finally, one point of note.  My panel cutout is about 0.7″ shorter in height than my real panel, so in reality I have a little bit more wiggle room to play with when stuffing various electrowhizzies onto the panel . . .  if it all fits on my mock up.


19 March 2014 — Thought I’d show a couple more of my Instrument Panel machinations. The first one below shows the real deal with the iPad Mini fired up with FlyQ EFB from AOPA, and my Android phone with the GRT app showing the Bluetooth wireless COM radio control function.

Chap 22 - Instrument PanelThe next picture shows my throwing the big 10.4″ HXr screen PFD back onto the panel to assess how it will fit.  A number of other items are on the panel to see if they fit, not necessarily in the location they’ll end up.  I also swapped out the Garmin GNS430W with the Garmin GTN650 (my actual panel is about 0.7″ higher than this one at the top middle, so even thought it looks like I’ve run out room, there still some more wiggle room left up along the top curve).

Chap 22 - Instrument Panel


16 April 2014 — So I’ve been working on my electrical system. I upgraded my electrical system diagrams from a Garmin GNS430W to the GTN650. I figure by the time I buy my main Nav GPS I won’t be wanting technology that’s on Garmin’s eventual chopping block for support. Of course with the move to the GTN650, I had to add two more Circuit Breakers to the panel since it’s a mandatory requirement for them that you use CBs and not fuses. Although admittedly two CBs for 7 wires is not bad.

I’ve also been spending some time on my throttle and stick (HOTAS) switches.  I reconfigured a number of switches between panel, throttle and stick, and in doing so was able to get rid of a couple panel switches.

Right now I’m thinking that if one has the panel real estate that the new Garmin G3X Touch is the way to go. As for me, I’m not burning that much real estate for an EFIS display. I decided that quite a while ago when I made a decision to forego the 10.4″ GRT HXr PFD for GRT’s much more manageable 8.4″ or 6.5″ PFD. Plus, as awesome as Garmin is, those bubbas tend not to play well with others’ stuff. I guess it’s a good marketing strategy, but picking up and using cool & useful third party stuff with Garmin can be problematic if ‘Big Brother G’ simply says, “No, you can’t use that crap with our suite of technological goodies! Here, use this nice GARMIN thing X instead!”

Also, now that I’m getting significantly closer to my final instrument panel and electrical system configuration, I’ve started building all my Wire Book templates.  I have about 20 total templates currently completed for all the various electrical subsystems, and I’ve built 5 system diagrams from these templates so far.  It should be slow steady progress over the next few months since each one that I build helps with building the remaining ones.


20 April 2014 — After squawking about the new Garmin G3X Touch being too expansive for my wee panel, I decided that I should thoroughly investigate it to ensure I wasn’t missing anything important.

Chap 22 - Garmin G3X Touch

So this past weekend I again built a matrix to compare all my EFIS options to ensure that I’m getting the best capabilities, cost benefits, and of course weight efficiency out of my EFIS that I possibly can.  Thus, I did a runoff betwixt the new Garmin G3X Touch, threw the close-sized GRT HXr 10.4 back into the mix, the GRT HX 8.4, and GRT HX 6.5.

Chap 22 - GRT HXr 10.4 EFISChap 22 - GRT HX EFIS

I then began to tally up all the weight, cost & current draw of all the components required to give me the capabilities I’m looking for in an EFIS system.  Something to note that in all of these configurations is that the second-screen MFD and back-up PFD is the GRT Mini-X.

Chap 22 - GRT Mini-X EFIS

I was surprised as I tallied up the prices that the cost difference between the Garmin G3X Touch and the GRT HXr was less than a grand.  As I trudged along in looking up component weights, and with things still looking comparable between the two systems (of course giving a slight performance edge in touchscreen simplicity to the Garmin), I hit a fairly significant snag.  It appears that Garmin’s remote transponder is a robust bubba, weighing in at over 3.4 pounds with an installation depth of over 11 inches. The weight on this one transponder helped get me back to reality, realizing that I was comparing the big heavy guys, when once again I was getting plenty of capability with the smaller, very capable “little guy” EFISs that were much lighter and offered much more panel space … and thus configuration options.  So once again, although tempted by cool colors and touchscreens, I dumped the big EFISs to return to smaller, lighter and more efficient.

One thing that came out of my EFIS comparison, was that I took a hard look at my allowable space BEHIND the instrument panel.  I pulled out the plan’s A-pages to measure out clearances and I had a true Doh! moment.  Albeit initially (Fall 2012) I had been verifying clearances behind the panel with cardboard mockups, since then I had been rearranging, adding, removing and modifying my avionics/instruments with apparent reckless abandon!  The result was that I was placing components in position on the front panel with assumed clearance behind the panel.

To remedy my ways, I gathered the physical data for the displays, avionics, instruments and components all going into the panel.  I clearly needed to deconflict my behind-the- panel space requirements to match what I could have on the front of the panel.  I will say that I attribute this epiphany in part to Nick Ugolini since I found while reviewing his blog that he had run into this snag while redoing his instrument panel.

A significant focus in this effort is of course the area immediately behind the lower right side panel, since the elevator control rod must have free reign in its movements.  I had stacked up my GNS430W/GTN650 over on the right side, having failed to verify it’s clearance with the elevator control rod, and then even added a couple of other rather deep instruments to boot.  I’m glad I found it now, but I admit it was not the most optimized planning on my part.

The result of all this was a trip back to the proverbial drawing board.  I got out my cardboard cutouts and begin putting all the “new” puzzle pieces in place.  The result is something along the lines of this:

Chap 22 - Instrument Panel

Again, I will make note that this is still a work in progress, but at least now I am very cautious about my specific clearances behind the panel.  In the back of my mind I thought I was doing this, but pulling out the actual plans verified and confirmed how little space there actually is behind our panels in these birds.  And of course we all know what assumptions get us!

Build on!



Recent Posts

Project Update

Hi Folks,

I’m still working out the finer details of making everything fit inside the cockpit, specifically the left armrest currently.  I can see a very real light at the end of the tunnel for all my in-cockpit install shenanigans, and expect to be done with those in the next 2-3 weeks.  

I will be heading out of town for a couple of weeks over the Thanksgiving holiday, but shortly after I return I expect to start working on the lower engine mount extrusions and hanging the engine mount itself in prep for the engine build that will take place somewhere between mid-December and mid-January.  In addition, I’ll mount the firewall in prep for the concurrent canopy and nose builds.

So the big build stuff is coming soon! (including the wheel pants…)



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