Panel Planning 101: Think, Draw, Cut

Avoid upgrade remorse by playing an active role in the avionics layout. One Mile Up's panel planning software is resourceful, but not the final tool.


Along with engine swaps, full-up avionics upgrades are the biggest investment you can make for your bird, and when you’re handed an invoice equal to the value of the aircraft, shouldn’t you fly away with the panel layout you want? Based on conversations we’ve had with buyers, that doesn’t always happen. Hold the cutting tools.

One of the problems is that the techs doing your upgrade may not be pilots, and that means they may not appreciate the importance of getting the right panel ergonomics. It could be as simple as misplaced rocker switches and warning lights or worse—the wrong placement of primary displays and autopilot control heads.

Luckily there are some things you can do to avoid this heartache, including using a good software program that accurately runs the layout possibilities for a given aircraft. Herewith is a guide for planning custom layouts—the first time.  

Dream Big, Think Practically

As with most big purchases, buyers tend to focus on flagship options, when in reality that’s out of the budget and perhaps excessive for the purpose. And that’s an important part of the planning that you as the aircraft owner and pilot need to nail: Define the purpose of the avionics upgrade. What you want might not be what you need—a topic for a separate article.

Once you decide on the gear that works for your flying and budget, you’ll need to determine if it will work in your panel. That could be as easy as using the existing round instrument cutouts (Garmin’s GI 275, the uAvionix AV30 and Aspen Evolution flight instruments are three examples), or as complex as having to cut a new metal panel.

Don’t forget to plan the panel lighting. The custom panel on this Piper Meridian has glareshield strip lighting that works well with the paint work.

The other thing to consider is required depth behind the panel. Some panels are deceiving—there may be lots of real estate on the surface of the panel but clearance behind it is an issue. Maybe some equipment will be in the way of the flight controls and maybe fuel lines, vacuum lines and wiring bundles are in the way.

One benefit of going with an all-electric avionics suite is the ability to remove the vacuum system, if the equipment configuration supports the regulatory requirements. Don’t underestimate the amount of space that’s required behind the panel for the vacuum lines and the central filtering system and even the depth that’s required of traditional flight instruments and gyros. Plus, without the vacuum lines in the way, the avionics will be easier to maintain and upgrade, moving forward. Think beyond the aesthetics.

This Baron went from an OEM panel to a custom metal dipped in carbon fiber during a Garmin TXi display upgrade (below). Photo courtesy of Sarasota Avionics.

Once you have a general idea of which equipment you want, fly the aircraft to a shop (or two or three) and ask to sit with a tech to brainstorm in front of the panel. Good shops will be patient and go the extra mile to help plan the layout. Once you’re seated in the cockpit together, ask if the shop representative is a pilot. Many are not, and that sometimes means they don’t appreciate the importance of a good flow. This includes placing critical systems like fuel indicators, engine monitors and backup flight instruments in the best locations.

For installation in certified aircraft, there are often layout requirements specified in the equipment’s STC, and also in the FAA’s advisory circular AC 423.1211-1C. This is so the instrument falls within a prescribed field of view—or the ability to effectively see the information when seated in the pilot’s seat. Additionally, some installation manuals specify a maximum distance between a navigator and its interfaced nav display. The installer will measure a straight-line distance from the radio stack to the display and will need to place the equipment within the confines of the STC. This usually isn’t a big factor on smaller panels, but in larger panels like the ones found in turboprops and even larger twins, your desired layout might be limited.

The manual for Garmin’s latest TXi-series STC’d retrofit flight display is pretty specific about how it needs to be installed on the panel. It has to be completely viewable and within reach when sitting in the pilot’s seat. Moreover, Garmin advises that the screen should be located as far up the instrument panel as practical, and not interfere with flight controls or control locks. 

Working with classics like the panel of the Naval N3N biplane is often limited by panel design.

We’ve seen installers locate primary flight displays in a way where the control knobs get in the way of removable control locks. It wasn’t caught until the owner actually flew the airplane home, tied it down and attempted to put the control lock in. That’s poor planning.

While the panel is torn down, it’s a good time to address worn shock mounts. Some panels float on damping mounts, but for some installations where a display has built-in AHARS (the Garmin TXi is one), the shock mounts have to come off.

Panel Planners

Leave the metal tools in the drawer. Garmin’s GI275 and the uAvionix AV30 electronic round-hole instruments are bolt-in when replacing analog ones.

Shops may use a variety of methods for planning a new custom panel, depending on who is doing the cutting. Some farm it out and others will cut in house. Some, not all, use panel planning software, and one popular program comes from Colorado-based One Mile Up. The company was started in 1988 as a graphics company, originally creating content for the government and its contractors. Turns out the demand was so high for aircraft drawings that it eventually branched out to create scaled drawings of military and general aviation aircraft. 

Save some money and use the old plastic overlays or boost the aesthetics and visibility by cutting a new overlay. Don’t forget paint and placarding.

The company offered us a version of its Panel Planner J, a program that works on Mac and PC and is available in pilot/owner and shop versions. We tried the $495 pilot/owner level software on a Mac and found that it had a thorough database of avionics (new and old), and it updates often to refresh new/updated models.

The interface is fairly utilitarian, which isn’t a bad thing. From the drop-down window on the left side of the workspace, you drag full-color realistic alpha-channeled images of instruments, avionics and in some cases cockpit accessories (annunciator panels, as an example) into place on an aircraft panel template. The company says there are roughly 2000 instruments/avionics components and roughly 800 panels to work with.

Garmin’s G3X Touch in a Grumman is all about cutting new metal.

We like that the Panel Planner software tracks total cost (list price of the equipment), its total weight and the peak current draw and then generates an equipment list. It has the capability to print actual-size hole-cutting templates and color mockups when connected to a desktop printer.

Ultimately the Panel Planner exports to a CAD file that a fabrication shop might be able to use. The program can’t account for some details, like actual space that’s available behind the panel, and it’s not the say-all for what will and won’t fit. 

Of course, some have drawn panels on their own using open-source CAD-style modeling software to design and lay out dimensionally accurate panel arrangements, and then export them as .stl files for CNC fabrication. There are also CNC-capable fabricators that will do the legwork if you provide an equipment list, images or drawings. Of the shops we polled, less than half use an official panel planning program. But we think they’re resourceful for the owners doing preliminary planning.   

The Right Shop

That’s what you’ll need when planning a panel—one that understands the importance of good ergonomics (see the sidebar below for more), and can keep your ideas on the rails. Remember, what you want won’t always be possible and good shops avoid surprises by keeping you involved in all stages of the project.

In our next panel upgrade series we’ll look at instrument and panel lighting options—a costly but necessary part of new panel fabrication.  

Hardware/Software Ergos: A Compromise

I was quite happy with the installation of the Garmin G500 TXi in my Mooney and when it was time to fly the new panel, realized the TXi can be configured in many ways, but the most common is the PFD on the left and the MFD on the right. Each screen has a dedicated concentric knob. When displaying simultaneously the PFD and MFD, the knobs control the relevant display.

During the panel layout process, I decided to add an optional control head for remotely controlling many of the PFD functions. The TXi allows two ways to handle most of the PFD functions—through touchscreen and through a dual concentric knob very similar to other Garmin products. The optional controller added dedicated buttons and knobs including heading bug, altimeter set and altitude preselect controls.

But there was a big problem that was not obvious to me at first. The heading bug control is located in the PFD control knob, now hidden behind the pilot’s yoke on the left side. To reach it, I had to move my right hand over the yoke, blocking out most of the PFD with my arm in a defensive position just to change the bug. I could also try to reach the knob using my left hand, which required a bit of contorting my hand—awkward when hand flying while using the left hand to fly.

A relatively easy solution was to flip the display in the configuration mode, PFD to the right, MFD to the left. In my case, this was never really an issue because the controller has a dedicated HDG bug that was easily accessible. I was lucky in that I decided to get the controller in the first place. However, I was completely unaware of the impact of the decision until the first flight. I mentioned this ergonomics issue (specifically the G500 TXi heading bug function) to Garmin at AirVenture as feedback.

Fast-forward to December 2020. New software for the G500 TXi was installed, and it now allows the MFD knob to toggle between MFD and PFD modes, adding more flexibility. However, the PFD knob remains dedicated to the PFD only. I did ask Garmin why the PFD knob is not able to toggle and got the standard response having something to do with certification.

My recommendation related to ergonomics is that placement of the components (and their accessibility to the controls) needs to be considered very seriously as part of any upgrade, but especially when stepping up from round gauges to glass. This is especially important to nail before any metal is cut for a new panel. Typically, an actual-size engineering drawing is first produced. It is great to see what the panel might look like, but because it is only a drawing, the rendering is not good enough as it is hard to visualize the controls, especially in the third dimension.

Work with avionics shops that allow customers to interact with the technicians. You can learn a lot from them. If the avionics shop also has pilots, that is even better.

— Luca Bencini

Sometimes the most well-thought-out layout—and avionics component design—creates some minor nuisances. For instance, in my Garmin-equipped Cessna 340, all the knobs on the PFD that adjust the heading, altitude, and such are on the left side of the bezel, where they sit just above the left horn of the control yoke.

So, when acknowledging a new heading or altitude, I’d be pushing the PTT on the yoke with my left hand, while awkwardly reaching all the way across to the left side of the panel with my right hand to make the adjustment. Even while the autopilot is flying, this cockpit version of the game Twister is a bother.

That’s until I mounted a parallel push-to-talk switch on the center console. Now, I can hit the PTT with my right hand and naturally adjust the heading or altitude with my right. Problem solved—but not without some shop labor.

— Frank Bowlin

This article originally appeared in the April 2021 issue of Aviation Consumer magazine.

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Larry Anglisano
Larry Anglisano is a regular AVweb contributor and the Editor in Chief of sister publication Aviation Consumer magazine. He's an active land, sea and glider pilot, and has over 30 years experience as an avionics tech.

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