Big Avionics Install: Avidyne IFD540

Like many pilots, I’ve slowly added “portable” equipment that is relatively inexpensive but ultimately clutters the cockpit.  I had three little units on the glareshield, an iPad (which will still be very useful for charts) and a portable Garmin 496 hanging off the glareshield lip.  All this is great stuff, but it adds to the workload to try keep three GPS units updated with the latest flight plan – or remember which isn’t updated and may be leading you in a different direction.

Storm cell 1280
Old Panel.  You can see that yellow transponder was the last piece of avionics that came with the plane in 1979. It had some issues.

I finally decided to upgrade to year 2020 compatible stuff along with traffic, weather and a modern (low-approach capable WAAS) GPS navigator.  I decided on an Avidyne instead of Garmin because currently Garmin offers touch-only displays and Avidyne has both touch and good old knobs and buttons. I kind of like knobs. Plus Avidyne is a little more cutting edge on features (like built-in wifi and Bluetooth).  I also got an Avidyne AXP340 transponder (required for the ADS-B out mandate), an MLB100 traffic/weather receiver and a cool but hard to install DAC GDC31 Roll Steering computer (fakes out the autopilot to closely follow the GPS instead of a heading bug).

I did the install myself, a huge job.  I spent quite a bit of time beforehand building schematics and spreadsheets of what I had in the panel (where the wires were) and what I planned to have in there later (where the wires need to now go, and which ones will be added).  Basically the old analog wires that move needles or connect to antennas get re-routed, and a bunch of new digital communication wires (because now everything talks to everything else) need to be added.

Yep, I might have to throw the airplane out


I had some of the tools but used this as an opportunity to load up on a few more, and I borrowed some expensive crimpers from my mechanic (who came and inspected at various points along the way).  I was certainly nervous, as the worst that could happen would be I screw up so totally I would have to throw the airplane away.  I really didn’t want to do that.

I went slow and double checked each wire as I cut, rerouted, crimped and connected.  I had to also rewire and install a new GPS antenna on top of the plane. I did make a few mistakes but overall the IFD 540 just plain worked when I turned it on.  Wow, I was impressed with myself.  That was many hundreds of wires, crimps and recrimps.

Building up connectors – doesn’t help that most wires are unmarked and white


On my first checkout flight I asked ATC for an altitude check saying I had a new transponder, which I had connected using the “new” method of digital RS232.  They said, “congratulations.  I show you at 2,500 feet”.  I said whoops, I’m actually at 4,300 feet and they said, “well, good luck with that”.  And that started a two month process of trying to find out why my transponder would not communicate with my altitude encoder.  I replaced the encoder, the wire and finally the transponder with no success. Extremely frustrating – I even put an oscilloscope on the wire to look at the signals and they were fine.  I never did figure it out.  I gave up in disgust and hooked it up the “old way” with analog 9-wire system that only has 100 foot resolution instead of 10 ft resolution that is better for traffic avoidance.

As I cut out old wires I threw them under the plane.  This is under the plane.


Reinstalling the 9 wires took me about 5 hours of crouching under the panel and my back finally gave out and I crawled to the car and went home.  So my complex GPS went in OK but a fairly simple transponder kind of kicked my butt.

“Bench testing” the damn, %*%$$% encoder and transponder, which work fine on my desk.


The little DAC GPSS thingy was the trickiest to install, having to dig deep in the panel to tie into the guidance wires between the HSI heading indicator and the autopilot.  I also had to measure certain voltages then add resistors and potentiometers to tune the system.  Wow, way more than crimping wires and kind of fun.  I got it installed and possibly working and went up to fly.  I programmed the GPS and pushed the button.  The airplane veered off course a little, then a lot, and then did some strange semi-random patterns in the sky.  Wow, not even close.  I had to laugh.  I wasn’t too disappointed because I bought the thing off ebay and if I couldn’t get it to work I’d just remove it.  Then I read the installation manual some more and a brief section said if the airplane turned the wrong way, ground a certain wire.  OK, I grounded that wire and bam, the airplane follows the magenta line on the GPS screen.  Very cool.  It works.

Overall it was a fun project and I look forward to the new traffic alerting system that should help while flying in congested airspace – or perhaps out in the middle of Nevada flying in the mid-teens where you least expect someone.

My new panel.  Pay no attention to the ugly hole and the black tape on the right panel.  That’s another project to fix those.


Using the 540 on my first real trip to avoid weather. Strange, but not much traffic out there that day. (BTW, it looks worse than it was – I’ll write a post on that trip).






7 thoughts on “Big Avionics Install: Avidyne IFD540

  1. Curtis Campi May, 2016 — 6:29 pm

    What you do with the other King navcom???

    Curtis 775-722-6342

    Typos the responsibility of Siri and Curtis’ crazy iPhone.


    1. Sorry, I traded it away for stuff.

  2. I’m very impressed. Doing my own plumbing seemed like enough of adventure into the unknown for me. Congratulations on not having to throw away the plane.

  3. Fantastic story. You rock. Check out this video that a friend sent to me. I thought of you. And what you two have created with each other and your children over the years. And all those important places together. Keep it up!


    1. Hi Derek,

      That was an awesome video. All those important places!

      Thanks, Ney

  4. Should I take that as a no? No answer. Saw an airplane just like ours missing wings headed up 101 on a flatbed yesterday. Just a coincidence?



    1. Should I take that as a no? No answer. Saw an airplane just like ours missing wings headed up 101 on a flatbed yesterday. Just a coincidence?

      Hi Derek,

      I must have missed a comment as I didn’t see a question anywhere. But no, not my plane on the flatbed, thank goodness. I’ll be flying down to see my kids in college this weekend. First Santa Cruz then San Luis Obispo. Hopefully not taking a flatbed home. – Ney

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