New avionics!

The redo of the panel avionics is done!

There is much to like here. The new panel is far more functional than the outgoing one.

Transponder – Garmin GTX-345

Kicking off this upgrade is the transponder, as ADS-B is the real reason this whole process started. Sitting where the Bendix/King KT-76C used to be, now lonely out on the right stack, is the GTX-345 ADS-B In and Out transponder. The plane is now fully 2020 compliant. The box also gets all the ADS-B In goodies displayed on the GTN-750. You now have Traffic and Weather available.

Note: you do not need to touch this box, so far away. It is paired up with the GTN-750, so the essential functions are all available from the much closer touchscreen. Though unassuming, this box should greatly increase situational awareness in the cockpit.

GPS Navigator – Garmin GTN-750

The star of the show is what replaced the Bendix/King KLN 94, KMD 550, and one of the KX 155A. The big and clear screen of the GTN-750 now dominates the center stack. There is no better GPS/NAV/COM on the market today.

As this is a WAAS receiver, the plane now has the capability of doing LPV approaches, something the KLN 94 could not. The GTX 345 feeds it ADS-B info to display and you can control the transponder with touchscreen controls on the GTN-750. Though the G5, it can now direct the autopilot with GPSS. Also, the CDI for this box is the G5.

NAV/COM Radio – Bendix/King KX 155A

This is a holdover from the previous panel. The old COM1 is now COM2. With a previously upgraded LED display to replace the failing EL display, this now means the plane has two glideslope receivers. The CDI for this box is still in upper location, as the GTN-750 uses the G5 for the CDI. This radio is still one of the best on the market and is actually a bit better than the one in the Garmin box.

Attitude Indicator – Garmin G5 AI

Commanding your attention in the middle of the six-pack is a Garmin G5 AI to replace the previous vacuum instrument. More than an AI, it includes airspeed, altimeter, VSI,  heading, and other functions. Though only primary for the AI, it renders the other round dials next to it redundant. This device is backed up with a battery, so that it will continue to run for nearly as long as a full tank of fuel.

Horizontal Situation Indicator – Garmin G5 HSI

Paired with the G5 AI above it, the G5 HSI introduces much new functionality. Replacing the previous vacuum DG, this is now a fully functional HSI being driven by the GTN-750. Also battery backed, it can be put into reversion mode to become an AI should the primary AI above it fail. Another bonus is that this box now runs GPSS! Turn on GPSS on the HSI and put the KAP-140 into HDG mode, and you now have perfect GPSS complete with turn anticipation. Watch the plane fly holds and approaches for you nearly hands off.

USB Ports – EI USB-6A

I got tired of noisy and inconvenient car chargers. On the left and right of this device are 2.1A of USB power. The top and the middle provide 1A. Your stuff stays charged, that simple.

Vacuum System – GONE

Yep. No more vacuum instruments. Goodbye vacuum issues. The only thing remaining from the old vacuum system is the inop gauge, and only because it’s shared with amp gauge.


This was a pricey upgrade, running about $36,000. Parts cost was roughly:

  • Garmin GTN-750: $14,800
  • Garmin GTX-345: $4,500
  • Garmin G5 AI: $2,100
  • Garmin G5 HSI: $2,800
  • EI USB-6A: $190
  • Vacuum removal: $150
  • Breaker panel: $240
  • Wiring: $160
  • Static system: $120

Pacific Coast Avionics charged 125 hours of labor to install all of this at $85/hour for a total of $10,600. It took four calendar weeks.

I’m raising the cost of a Hobbs hour to $164. I think this is quite fair, as the function is much increased, but is still a significant savings over the G1000 Skyhawks.


New avionics!

9 thoughts on “New avionics!

  1. Glenn says:

    I flew 194SP yesterday for the first time after the major avionics upgrade. I also just found your website (good idea to post the URL in the plane). Loved the new GPS/touchscreen. Traffic info is always great in the bay area as I’m sure you know. I also appreciate seeing the ongoing costs/challenges of maintaining a plane on the line. Any chance you can post the manuals for the new avionics w/WVFC?


    1. Hi Glenn,

      Glad you like the plane. Seems popular after the panel upgrade…it’s flying many hours.

      Manuals…that was a miss on my part. Yes, let me get those added! Thank you for the reminder.


      1. dndx says:

        Maybe update the SPECS page on the blog and put manuals there as well. Although I did found them quite easily online with some Googling. – Datong


  2. Bert Argo says:

    How many hours is your airplane flying. I own 339SP and have it on lease back in Torrance, Ca. Thinking of the same upgrade, but would feel more comfortable if there was at least a little business advantage. My airplane had about 400 Hobbs revenue hours last year. Love to hear from you.


    1. The plane is flying an average of 35-40 hours each month. The new panel seems to have added around 5 hours to that total. 400 Hobbs is the region my plane is flying as well. I was also able to bump the price $10/hour without a drop in usage.

      It won’t pay back into your pocket very quickly. It’s a giant cash sink. What it does do is significantly raise the value of you aircraft. Of the $37,000 I spent, $18,000 came back in hull value. I was also able to sell $5,000 in old equipment. That makes the bill easier to swallow. That, in turn, is offset by higher insurance and property tax. An unknown is how much money will be saved not having a vacuum system. I’m figuring about $500/year in not having to check and replace vacuum pumps. Another unknown is what is saved in ditching two spinning gyros. I had been replacing those at the rate of about one a year. Maybe another $1000/year in savings.

      In the end, it makes sense. But it’s a hell of check to cut!


      1. Bert says:

        Thanks for your reply. My 339SP flew 51 Hobbs revenue hours in January at $169.95 (I get $135.96). But expenses do eat it up. I might just bite the bulletin and do it this year. Thinking about going to Sun n Fun to get sold. What hourly rate do you get. Thanks in advance for info. Bert


      2. The work was 125 hours at $85/hour at PCA. I flew the plane to Oregon to get the work done. Looks like you’ve already had the ADS-B Out work done with the KT-74. So, that’s covered and saves about $6000. Without ADS-B In, the big screen is less needed, so you could save another $5000 by going with the GTN-650 instead of the 750. My guess is your bill would be around $10,000 less than mine. The shop indicated that I could retain the KMD 550, if I wanted, but mine had a fault.


      3. Bert says:

        Thanks again. I meant “what hourly rental rate do you get?” Wish there was a discussion board of 172 lessors. You must be pretty good with WordPress. Why not start one. Bert Argo


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