December 15, 2019

Instrument Panel Planning

In addition to working out plumbing for fuel and brakes, I’ve spent a lot of time the last two weeks investigating the various avionics options available. I have to do this now because I haven’t settled on what my avionics suite will be. While most avionics are wired similarly, there are some differences, which will affect what wires I run through the fuselage and to where. Some autopilot servos use serial lines, others use CAN, but I think I can use the same wire for both. Garmin autopilot servos can control the electric elevator trim tab servo, so I would wire it directly to the servo; other vendors don’t have that capability, so I’d have to run the wires up to the front.

A good portion of my flying will be cross-country, so I need to be able to enter most airspace types on the east coast, in both VFR and IFR flight rules. My requirements are:

  1. EFIS Primary Flight Display (required), EFIS Multi-function Display (nice-to-have) for moving map & redundancy
  2. Compliant with ADS-B Out 2020 Mandate, ADS-B in capable
  3. IFR approach capable (LPV required, ILS nice-to-have)
  4. Dual-axis autopilot capable, capable of being coupled to the GPS for approaches
  5. Dedicated autopilot controls
  6. Engine Information System (EIS) linked into the EFIS
  7. Radios, Audio Mixer, Transponder, and Autopilot controllable through the EFIS

Here’s a Garmin G3X setup installed on a Grumman Tiger that I consider to be my model, though I would probably lose the COM/NAV and audio panels to save space:

My baseline plan was to build a panel out of the Garmin G3X line like the picture, with a 10″ PFD and 7″ portrait MFD as the heart of the system. I started reconsidering that plan as I priced out all the components needed – there are a lot of little boxes at $500-1500 each that you need to buy to have a truly integrated experience, plus lots of $30-$70 connector/installation kits. I don’t like that Garmin keeps their comms protocol proprietary – they don’t play nice with other vendor’s products. On the other hand, Garmin is really the only company that offers a comprehensive set of avionics, whereas everyone else is reliant on other vendors for some of the avionics suite. Of particular note: the Garmin GNX 375, which is a newly-released TSO-compliant IFR GPS navigator, with an integrated ADS-B in/out ES transponder for $7000, really has no peers. But the G3X is the only system that can fully take advantage of its capabilities, since they’ve made some of the interface proprietary (especially ADS-B traffic and weather).

Here’s a short summary of the options I’m investigating:

  • Garmin G3X: this is my baseline choice, and currently my favored option. This suite offers the best integrated experience in my opinion. I also think it will offer me the best longevity and resale value down the line, should I ever decide to sell my plane. Now that G3X is offered to certificated planes via STC/AML, I expect a lot more planes will feature G3X cockpits, so having this commonality is another strong point in Garmin’s favor. Dynon and Bendix are also offering versions of their EFIS’s for certificated planes; GRT and MGL are not (and have no plans to do so).
  • Grand Rapids Technology (GRT): makes the Horizon 10.1 and HRx. As I started pricing out a complete system based on their components, it fell within a few hundred dollars of a competitive Garmin system and doesn’t really offer any advantages – except that the MFD could be larger (10″ vs. 7″). A big negative in my opinion is that I would have to buy avionics from a slew of different companies to achieve the desired functionality: GRT for EFIS/EIS; uAvionix for ADS-B; Sandia or Trig for Transponder; PS Engineering for audio panel; Trig, MGL, Garmin or Val for comms; Garmin for GPS navigator. There’s no guarantee of everything integrating nicely today or in the future. GRT touts third-party integration as a strength, and I agree that it’s a good idea — but that falls largely on GRT, and I’d have to talk more with them to get a better feeling on how well they’ll support their products and integrations.
  • Dynon Skyview HDX: looks nice, very similar to G3x. Dynon doesn’t make an IFR GPS navigator, so I’d have a Garmin GPS anyway. There’s no price/weight/capability advantage to Dynon over Garmin, so I might as well stick to Garmin.
  • MGL Avionics iEFIS: looks nice on paper. MGL is somehow loosely associated with TAF, but even TAF is using Garmin for their fleet now, so that’s a statement in itself. The MGL iEFIS is somewhere in the middle to end of its life; from what I can tell, it was first launched around 2012-2013, so it would potentially be 10 years old already by the time I get to my first flight. MGL is really good about documenting their interfaces (their CAN protocol is fully documented), and they do give you a lot of customization options. If they have a tech refresh in the works, I might give this one another look. They just released a new V16 comms radio that looks really spiffy. Like other non-Garmin options, to be ADS-out compliant and also to get ADS-B in requires a cocktail of devices. When you put all this together, it’s not much less expensive than a Garmin suite.
  • Bendix King xVue Touch: This is a new option announced at Oshkosh 2018. They say it’s derived from the Honeywell Primus Epic / Apex flight display systems used on jets, and it sure does look pretty. But it doesn’t currently support any EIS, radio, or transponder integration, even after a year on the market; they say it’s coming. Bendix recently acquired Trutrak, so it would make sense that they would integrate full AP capability. The display is priced at $5500, which seems steep, but you have to consider that the AHRS is built into the display; others make you buy the AHRS as a separate box for $1k-2k, so the price is actually pretty competitive. I’ll be keeping an eye on this option, and see when they plan to roll out an integrated EIS and radio software update. On the downside, reading through online forums, there doesn’t seem to be a very high opinion of Bendix/King these days, as they mostly abandoned the small-plane GA market a while ago. The glossy brochure boasts about easy software updates via Wifi, but they haven’t released a single update yet according to the support site.

So with all this said, I’m going to proceed with wiring for the G3X system, and keep an eye on the options. I’ll hold off on buying any avionics components for now; I really don’t need anything until I’m much closer to completion, as long as I stick to a plan.

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