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Avionics Upgrade Philosophy

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walkinghispath

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I just read the article “So Long, VHF Nav” in the March 2020 issue of Aviation Consumer. At the end it asked readers to share their avionics upgrade plans, so I wrote the following. I figured some of y’all might also find the information useful.


I am a CFI/II (helicopter, ASEL), commercial multi pilot, and an A&P. I own a Seneca II and two Cherokee 140s that I lease to our club and give instruction in.

I’m currently in the process of an avionics “harmonization” project in order to make transitions between the aircraft as seamless as possible.

I believe money is best spent on capability, not beauty, bells, and whistles, so I went with all used avionics. I’m setting up one 140 as a primary trainer, the other as an instrument/commercial trainer, and the Seneca as a multi-engine trainer/family vacation machine.

So, the stacks are as follows:
Primary trainer-
GMA340
GNS480
SL40
GTX327 (GDL82 ADS-B)

Instrument/Commercial Trainer-
GMA340
GNS480
SL30
GTX330 (GDL82 ADS-B)

Seneca-
SL-15M
GNS480
SL30
GTX330ES

ADS-B In for all aircraft are Stratux boxes I built and connected to external antennas. Old DME antennas are great for 978 MHz FIS-B and TIS-B reception. The old ADF sense antenna mounting post location on top of the fuselage is an easy place to add an external 1090 antenna to receive traffic directly from other aircraft transponders. The existing coax can usually be reused for this purpose, so there’s no need to pull down the headliner.

With a common stack and universal ADS-B In solution, the students that fly my aircraft won’t have to learn different avionics with the hobbs meter running and can focus on the task at hand. RAM X-grip mounts are available in each plans so the student and instructor can use whichever EFB they have.

I chose the GMA340 because it has a couple slide-in upgrade options from Avidyne and PS Engineering. The SL-15M in the Seneca will be upgraded when the other two are, but as it’s already a push-button com panel/intercom I elected to leave it in place until the fleet upgrade.

The CNX80/GNS480 is the best value in GPS/NAV/COMs as it can fly every CAT-I ILS and GPS approach in the world. I also prefer the Apollo interface to the Garmin (430/530) as the menu layers are shallower and flight plan changes can be made without effecting the active flight plan. It uses a standard compact flash card for databases and there is no limit on capacity, so it can continue to grow as new approaches and waypoints are added. It was also designed alongside the SL30 NAV/Com, SL40 Com, and SL70 transponder so those devices all work together to share data such as frequencies, GPS-derived DME, squawk code, and TIS-A traffic information. The capabilities of the SL70 found their way into the digital GTX line after Garmin acquired UPSAT, so they’re also compatible.

The GNS480, SL30, and SL40 are also capable of monitoring their standby com frequencies, but those are muted if a transmission breaks squelch on the active freq. This allows each airplane to simultaneously monitor 4 com frequencies. With the “Com 1/2” feature of the com panels, the workload can be split and each front seat can manage two com radios.

The SL30, in my opinion, is the best NAV/COM ever produced. The RS232 interface allows it to communicate with the GNS480 in order to receive frequencies from its database and GPS-derived distance to a tuned navaid that can then be displayed on the SL30’s screen. It can also display the selected OBS from a connected CDI (useful for troubleshooting) as well as a digital readout of the radial the airplane is currently on. When I got the radios in the mail I took them to my local avionics shop to see if they could test them. They said they couldn’t, it was too old, but they would happily sell me a new Garmin unit. I declined. The “new” G-box has no more capability than the SL30, but in a larger form factor. I built my own test cables and both radios worked flawlessly.

The transponders receive air/ground commands from the 480s as well as WAAS position for ADS-B out (direct to the 330ES or to the GDL82s as applicable).

As previously stated, I am rather frugal. So this entire upgrade was nearly cost-neutral. The Seneca already had a GNS480, SL40, and GTX330ES when I bought it. The other 480s cost me $3500 each, the SL30s cost $2500 each, and the GMA340s were $700 each. The GTX327 was in one of the 140s and the additional 330 cost me $500. Pins, wire, and connectors were about $100.

All told I’m into the project for about $14,000. However, the avionics I pulled and will pull as I complete each aircraft will help offset that cost significantly. The units and their street values are as follows:

2x MX170C $2500 each
Garmin 696 w/ mount, external antenna, and cables $1000
KN 73 Glideslope receiver $50
PMA6000M-C Audio Panel $700
KR87 ADF w/tray, KI-227 slaved indicator, and antenna $500
KNS80 $800
KLN94 w/tray, MD40-65L CDI and antenna $1000
KX155 w/glideslope $1500
KX155 w/o glideslope $1200

That brings the recouped costs to $11,120. So, not counting my time for the installations, this whole project has a net cost of $2880!

Now, this is only phase one of my upgrade path. Next up is Dynon Skyview HDX for all of the aircraft and autopilot for the instrument/commercial trainer and the Seneca. But that’s dependent on the timing of the STC being issued by the FAA.

Interestingly, this next phase will also have significant cost reductions from selling the old equipment. CDIs, HSIs and annunciators all still have value for those that wish to keep their legacy systems running.

Here are some before/during/after pics of the Seneca panel:


Additional equipment I’ve installed include engine monitor and storm scope. The JPI EDM line is the best value in engine monitoring that I’ve found. I installed an EDM800 in the primary trainer and have an EDM700 with fuel flow and USB that’s going into the instrument/commercial bird. The Seneca had an EI single-temperature gauge for each engine with rotary switches to select individual EGT, CHT, Oil Temp, or OAT sensors. Those sensors were all compatible with the EDM760 with fuel flow and USB that I installed.

The EDMs all connect to the GNS480s for mpg/destination/reserve fuel data.

The Insight StrikeFinder antenna replaced the ADF antenna and the indicator is connected to the bootstrap output of the KI-525A so the displayed strikes and cells remain pictorially accurate even when turning.
 

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