Avionics: New indicator lights circuit board.

I decided to preemptively replace my Plane Power AL12-EI60 alternator at 513 hours.  It whines like a coyote whereas my backup B&C BC410-H is as quiet as a mouse.  Late last year, B&C released the SF601 internally regulated alternator which is what I went with.  

That new B&C alternator doesn't have an indicator output so I redesigned my indicator circuit board to make the ALT indicator a low voltage light and also made each flight flash when they are enabled (other than the pitot heat light, because that would be annoying) to help grab my attention.  The new board also uses quick-connect tabs to make servicing it easier and it has less exposed trace area.  And since the ALT light is now a low voltage light, I won't need that tiny circuit board I made to ensure the ALT light always indicated the status of which of the two alternators was selected.

Here's what the new board looks like in CAD (easier to make out the details with the CAD rendering than with an actual image of the board).  The other side of the board attaches to the LEDs and indicator test push button.  After I soldered it up, I sealed it with lacquer.

The following schematic outlines what I designed.  A 555 timer is used for a T_On of ~0.7 s and a T_Off of ~0.3 s.  Since the 555 can't source much current, it controls a high side PFET which connects and disconnects +12 V from the LEDs in concert with the 555's Q output.  The Canopy Open and Oil Pressure LEDs will thus blink when enabled (active low). 

Q2's base is pulled high by the PFET output which normally enables the ALT LED.  But a 13 V Zener diode with a few resistors will break down above about 13.7 V, causing Q1 to turn on which turns off Q2, which shuts off the ALT light.  Thus the ALT light will be off when the main bus voltage is about 13.7 V and higher and blinking when it's lower than 13.7 V, indicating a low voltage situation on the main bus.

A 1 μF bypass cap on the power input was necessary to clean up the 555's output.  And a 3.3 μF cap was necessary across the ALT LED since when the PFET turns off, the LEDs' power line drops below 13.7 V, causing a dim and momentary flash on the ALT LED even when the bus voltage is higher than 13.7 V.  That 3.3 μF cap across the ALT LED holds the voltage high enough for long enough during the T_Off phase that the LED won't briefly try to turn on.  Since it's only 3.3 μF, it doesn't cause the ALT LED to fade off when being illuminated.  Capacitors across the Canopy Open and Oil Pressure LEDs aren't necessary since when they are not illuminated, their cathodes are floating so there is no current path available.

As before, an "indicator test" input will momentarily turn on all LEDs to verify they work.  This would cause the Oil Pressure, Canopy Open and ALT LEDs to flash and the Pitot Heat light to turn on solid.

Video showing canopy being locked/unlocked with lights flashing.

Circuit board parts list:

• 555 timer:  Texas Instruments SE555DR
• Capacitor 3.3 μF:  Nichicon UVR2A3R3MDD
• Capacitor 1 μF:  Nichicon UPX1V010MPD
• Diodes:  Kyocera AVX SD1206S040S2R0
• PFET:  Infineon Technologies:  IPP120P04P4L03AKSA2
• Quick connect tab, 0.25":  Keystone Electronics 4902
• Resistor 4.7 k:  Panasonic Electronic Components ERJ-8GEYJ472V
• Resistor 10 k:  Panasonic Electronic Components ERJ-8GEYJ103V
• Resistor 270:  Panasonic Electronic Components ERJ-8GEYJ271V
• Transistor:  onsemi MMBT2222ALT1G
• Zener 13 V:  Microchip Technology 2EZ13D5

Avionics: Oil quantity sensor installed.

Following my experience with the failed Airflow Systems 2007X cooler, I wanted to have an indication of how much oil was in the sump during flight.  Aircraft Extras makes just such a product.  The sensor, contained in a tube welded to a fitting, is placed in an unused drain plug.  The sensor wires are routed through the firewall into the electronics box which, following calibration by the user (filling an empty sump with a series of known increments of oil), in my case connects to my EFIS for display of the oil quantity.  I also got the optional temperature sensor since...well...why not?  

Below is an image of the sensor as delivered for my engine (Lycoming IO-390-EXP119) and the electronics box (pic from Aircraft Extras).  The design of this sensor is exceptional and seemingly all possible use cases were thought of by Aircraft Extras.  E.g., separate indicator lights (if not used in conjunction with an EFIS) can be accommodated and a remote programming button is supported should the electronics box be mounted in an inaccessible location.

To order the sensor, one needs to make a measurement to determine what length sensor is appropriate for the engine.  Below shows the oil plugs for my engine (IO-390-C/EXP119) looking up at the sump where the top of the figure is the aft side (taken from the Lycoming maintenance manual, MM-IO-390-C Series, page 72-20).  The oil drain plug is circled in red whereas the right forward plug is circled in green.  For reference, my sump is Lycoming part 56B28511.

 

 

Below left is an image of my sump before it was installed (from back when I changed my engine to the -EXP119 variant) and the right shows the engine without the sump.  Based on these two images, it seemed reasonable that the right forward drain plug would capture a significant volume of oil via the sensor (the plug next to the oil screen, the lowest spot on the sump, is used for draining and is thus unavailable).  I measured 4 and 5/16" from the bottom of the sump to the ceiling.  Thus my sensor length was 4.065"  and I thought 60" length cables were appropriate for my installation. This yields Aircraft Extras part S4.06-1/2NPT-C60.  

Below shows the sensor installed.  I added heat shields along the two nearest exhaust tubes (only one of which is visible) to help deflect heat away from the coax.

I calibrated the sensor using 0.5 quart increments up to the max of 7 quarts.  Following calibration, my sensor output about 4.2 V (out of 5 V possible) at 7 quarts.  Obviously, that's not the full 5 V output.  So using a 7/5 scaling, that translates to about a maximum of 5.9 quarts readable (i.e., the remaining 1.1 quarts were above the top of the sensor and not available for measurement).  That's great since I don't usually fill beyond 6 quarts so I would be able to see a meaningful reduction in oil in flight (however, read the last paragraph below to understand how to interpret the sensor's indication in flight).  On my next oil change, I'll recalibrate the sensor up to a 6 quart max so the sensor output has more resolution.

My panel just doesn't have space to mount the electronics box anywhere other than in the map box cutout.  It wasn't practical to use screws, so I cinched it down with wire ties to the SkyRadar mount (which is now a Stratux mount).   After this image was taken, I used a pair of right-angle SMA adapters to better route the coaxes.  I didn't have the right tool to cleanly crimp the sleeves on the connectors, so the former look a little flat.  If you're curious why there's a USB power socket adjacent to the electronics box, go here.

Wiring map for the electronics box is below.  It shares its power by connecting to my Aircraft Extras Fuel Guardian and thus is protected by that 1 A fuse (which also powers my CO Guardian).  The sensor is configured to have 0-5 V outputs for both outputs with 0-300 °F scaling for the temperature output.

Here is an image from my EFIS in flight showing the sump temperature and oil quantity (bottom right two meters).  It's interesting that the sump temperature (where oil collects before the oil cooler) shows only a few degrees higher than at the oil cooler exit.  I would have expected a larger temperature difference between the two locations.  However, these sensors may not have similar accuracies.  An explanation for the oil quantity indicating lower than actual follows.

Here is a graph from a flight showing the oil pressure, oil quantity and sump temperature.  The x-axis is the time in minutes since start.  It's interesting any time the OilP goes up, the oil quantity goes down.  I think this is because at high OilP there is a high volume of oil moving out of the sump.  Thus, the oil may not have enough time to settle and collect at the front of the sump (where the sensor is) before the oil pump pulls it through the screen (I presume high OilP translates to a high volume of oil moving).  

Thus, in my case, the sensor always gives an artificially low number when the engine is running and as power increases, the indicated oil quantity is reduced accordingly.  I have the EFIS "low oil" alarm set to 3 quarts for now (which translates to maybe 5.6 quarts of actual volume in flight).  I will experiment with that setting over time to get me an active alarm around 5 quarts of actual volume in the engine in flight.

Avionics: B&C SF601 alternator replaces PlanePower AL12-EI60.

I decided to preemptively replace my PlanePower AL12-EI60 alternator at 513 hours.  It whines like a coyote despite the alternator filter, whereas my backup B&C BC410-H is as quiet as a mouse.  Late last year, B&C released the SF601 internally regulated alternator which is what I went with.  

Here are the differences I noted between the B&C and PlanePower.  No claims on if any of these are significant in any way.

• The B&C has no low voltage indicator light output.  So I needed to redesign my panel indicator board.
  
• The B&C tension arm bracket is longer, so I had to translate the forward heat muff outboard so its SCAT tube doesn't impinge on the bracket.
• The B&C brackets are not cadmium plated.
• B&C alternator is about 2 ounces heavier than the PlanePower.
• The bolt that holds the B&C alternator to the boss bracket is smaller in diameter.
• There is no bracket between the starter and B&C alternator like for the PlanePower (part V-1002 on plans page 43-12, shown below in red); Part V-1002 won't fit.  Looking at plans drawing, I'm curious why Van's included that bracket and why B&C didn't.

On the phone, the B&C tech told me that my alternator belt would need to be changed since the stock belt isn't the right length.  Turns out that they sent me the same Dayco 15355 belt that I already was using, so no belt change was necessary. 

My new B&C alternator also whines like a coyote.  Oh well!

 

Avionics: Connected right EFIS to backup battery and installed switch.

Since I installed dual SureFly ignition in my airplane, having a fully electronic ignition means being thoughtful and deliberate about how those magnetos get their power.  Speficially, one needs a backup battery and a means to control how that battery is connected to the ignition and the main bus.  After designing and installing my backup battery system and realizing it has a lot more capacity than necessary for the SureFly, I connected my AHRS and left EFIS to the backup battery (shown towards the bottom of that post).  I did so through a locking DPDT panel switch that lets me disconnect the left EFIS from the both sources of power (primary and backup) simultaneously.

I decided to do something similar for the right EFIS.  I connected it to the backup battery also but instead, used a DP3T switch so I have the following three switch functions:  1) OFF, 2) primary only and 3) backup and primary.  For that switch, I used a NKK Switches M2044LL1W01-C to match the switch I have for the left EFIS.  Here is that switch newly installed on my panel.

 

Here is the pinout and connection information for the new switch.

Here the switch for the left EFIS, which I added when I swapped over to fully electronic ignition and installed the backup battery.

These switches are really most useful for when I need to update the EFIS databases.  I no longer need to switch on the entire panel.

Avionics: Replaced GRT HXr EFIS fan.

The fan on my right GRT HXr EFIS has been making a racket on startup for years.  GRT says that the fan is a Sunon MC25101V2-000U-A99.  That fan is no longer manufactured, but I found the MF25101V2-1000U-A99 which is.  Turns out it moves a bit more air and uses a bit less current than the one it replaced.  So, win-win!

Removal of the EFIS for surgery. 

The fan is not designed to be field replaced.  You need to take apart the back of the EFIS to access the fan.  

And its wires are soldered on the reverse side of a circuit board.  

Rather than trying to fuss with desoldering those wires, I just cut them and spliced in the new fan with a few layers of heat shrink tubing for additional insulation.

Then the wires are tucked back in and the EFIS is reassembled.

 Success.

Avionics: Electronic ignition backup battery and controller.

Since I installed dual SureFly ignition in my airplane, having a fully electronic ignition means being thoughtful and deliberate about how those magnetos get their power, i.e., one needs a backup battery and a means to control how that battery is connected to the ignition and the main bus.  The SureFly's STC points to the guidance in the install instructions on how the backup system should be designed.  Below I outline my approach which closely follows that guidance.

In selecting the backup battery,  I wanted something very light, in front of the firewall and that could hold enough energy for at least an hour of flight under non-ideal conditions (i.e., a tired or somewhat discharged battery). I didn't want to use the TCW backup battery because it's very expensive, large, seems difficult (and costly) to replace when the time comes and doesn't give me flexibility in controlling its behavior.

In my case, I decided that the EarthX ETZ5G battery would be a good fit, at 3.4 Ah and 1.15 pounds and no-load, fully-charged, nominal voltage of 13.2 V.  This battery would ideally provide 3.4 hours of run time for a single SureFly, so factoring in non-ideal conditions, it seems more than adequate.

There were two reasonable locations to place the battery.  One was above the main Odyssey battery on the ride side of the firewall.  The issue with that location was that I'd need to drill into the firewall to mount the EarthX battery.  I didn't want to add more holes, so I decided to mount the battery below my GPS antenna shelf on the left upper firewall by using a bolt on that shelf and two bolts that hold the AHRS tray to the backside of the firewall.  

Below shows the EarthX battery situated in the proposed location.  I anticipate replacing this battery every 5 years.  Having the battery located here means it makes sense to have the backup battery connected to the left SureFly and the main battery connected to the right SureFly.

With my newly developed 3D CAD skills resulting from my larger oil cooler modification, I designed a mounting tray for the battery using OnShape (EarthX didn't offer a tray for this specific battery).  The design includes provisions for riveting it together, holding tabs, mounting plate and mounting holes for a circuit board whose design I'll explain later in this post.  Below is an isometric view and various images of the design.  My design was fabricated by SendCutSend for $57.06 shipped.

 

The design includes a plate that attaches to the outboard hole of the GPS antenna shelf (which is really the upper left outboard hole of the AHRS tray) and the bottom two holes of the AHRS tray (shown on left image below).  SendCutSend doesn't do joggles, so I did that one myself.  Then I used clay to locate and drill the upper bolt hole.  That's the left image below.

After the parts were primed, the battery tray was riveted together then riveted to that plate as shown in the right image below.  Then the battery was mounted as shown on the lower image below.  Note, you can also see the initial revision of a circuit board I designed, the final revision of which I'll explain next.

Note:  In the above image, you can see how I grounded the battery.  I used a 1/16" piece of aluminum to bolt to the negative terminal and then a screw into the battery tray.  Since the tray is riveted to the mounting plate, which itself is bolted to the firewall, this seemed a great approach rather than using a wire.

Having a backup battery requires one to have some means to control how its energy is accessed and replenished and having a means to isolate that battery from the main bus so that it doesn't power the main bus and only powers what it's intended to power.   

My requirements for the backup battery controller circuit board that I would design included:

• Backup battery can't provide energy to the main bus.
• Backup battery charging available by the main bus.
• Pilot can control when the backup battery can be charged.
• In my implementation, when the main bus voltage is above ~13.7 V, if an alternator is engaged, backup battery charging is available.  Though one could use a dedicated switch if desired.
• Very low energy loss through the circuit.
• No diodes used as a primary means of current control.  
• High side PFET control has negligible loss when enabled (~ 5 mΩ).
• Left SureFly connected to the battery with the highest voltage at all times.
• If the main bus fails to a short or open, the backup battery can still feed the SureFly.
• If the backup battery fails to a short or open, the primary battery can still feed the SureFly.
  
• Left SureFly power not interrupted if board loses its ground connection.
• The SureFly still receives power from the battery with the highest voltage.
• Without ground, the backup battery cannot be charged, however the EFIS would indicate the backup battery not being connected to the main bus, alerting the pilot to the issue.
• Redundancy in case of discrete device failure. 
• Resistor/diode/transistor failure(s) or disconnects won't interrupt power to the SureFly.
• One PFET in each pair can fail and the circuit will still work at the expected current loads.
• If either pair of PFETs fail, the other pair will continue to power the SureFly.  The backup battery will be disconnected from the main bus and the EFIS will indicate the voltage mismatch alerting pilot to the issue.
• Up to three PFETs can fail and the SureFly will still receive power. 
• Two Zener diodes are used as voltage sensors such that a failure of one can be well-tolerated.
• Can tolerate excessive voltage inputs.
• PFETs and NPNs are tolerant to 40 V.  With a 1 kΩ current limiting resistor, the Zener is tolerant to well above 40 V.  This is above the ~30 V maximum of most of the onboard avionics.
• Can power other devices directly from the backup battery.
  
• Allows for power up of the EFIS and AHRS before engine start.
• Allows for monitoring the backup battery voltage.   
  
• Fuses to protect circuit board and associated external connections.
• The main battery input wire is fused externally before connecting to the board. 
• LEDs to indicate circuit state (useful only for testing on the ground):
• Red LED indicating when the main bus exceeds 13.7 V.
• Green LED indicating when backup battery charging enabled.
  
• Moisture/oil impervious.
• Circuit board coated in acrylic and mounted in a water resistant box.
• All copper traces must be of adequate dimensions for carrying expected current loads.  
• Minimum of parts and none specialized.

Here is the circuit board I eventually designed to fit all my criteria.  This was my fifth revision of the design and is my final design.  I used KiCAD for the layout and OSH Park for board fabrication.  This CAD model shows the fuses installed.  The schematic is shown further below.

The below shows the board during bench testing (technically, this is kitchen table testing).  The green LED shows when an "ALT FIELD" input to the board is enabled (active high) and the backup battery can receive current from the main bus for charging.  The red LED shows when the main bus is above about 13.7 V and the "ALT FIELD" input is enabled.  That threshold ensures that the backup battery is isolated from the main bus when the main bus voltage is too low, thus preventing the backup battery from powering the main bus. 

The schematic is shown below.  Paired PFETs are used for redundancy and load balancing (though the latter isn't needed given the specs of the PFETs).  The PFETs are connected such that, when not enabled, their body diodes always allow the left SureFly access to the battery with the highest voltage and prevents the backup battery from powering the main bus and the main bus from recharging the backup battery.  Thus the left SureFly is always energized regardless of the board's state (i.e., no matter the "ALT FIELD" input or main bus voltage).

When the main bus exceeds about 13.7 V, the Zener breaks down, allowing Q6 to turn on but only if Q7 is also on (which itself only turns on if an alternator is selected with the main bus voltage > 13.7 V).  At that point all the PFETs turn on, bypassing their lossy body diodes, directly connecting the main bus to the backup battery for charging.  Thus the backup battery can never power the main bus when the main bus voltage is below 13.7 V, a value well above the nominal voltage of the backup battery.

The 1k-ohm resistor between the Zener and the base of Q6 is to limit the current in the Zener.  This resistor will slightly raise the threshold of the Zener's breakdown voltage.  The value of that resistor can be selected to increase the Zener's breakdown a few tenths of volts and/or compensate for tolerance variations in individual diodes.  In my case, 1k was the ticket.

Running through scenarios for an isolated failure of the Zener diode in the schematic above:

• Zener fails to open circuit:
• Surefly remains connected to the battery with the greatest voltage.  
• The backup battery cannot be connected to the main bus for charging.
• This state will be indicated on the EFIS by the backup battery being a lower voltage than the main bus voltage. 
• Zener fails to short circuit:
• Surefly remains connected to the battery with the greatest voltage. 
• Main bus voltage > 13.7 V:
• Regardless of alternator operation status, this is not an issue since the main bus voltage exceeds the nominal voltage of the backup battery. 
• EFIS indicates that backup battery voltage is lower than main bus voltage. 
• Main bus voltage < 13.7 V (e.g., alternator off)
• The upper PFETs cannot be turned on since the Zener diode on the alternator switch board (explained later below) is not in breakdown so the "ALT FIELD" input is not enabled.  Thus the upper PFETs' body diodes prevent connecting the backup battery to the main bus.
• EFIS indicates that backup battery voltage is different than the main bus voltage.
• Red LED on circuit board is illuminated even when the voltage on the board's "ALT FIELD" input is artificially forced below 13.7 V.  This is an indication of Zener being shorted and is part of my condition inspection check.

Below is the CAD image of the box design.  It includes integrated standoffs for the circuit board.  Four single screws are intended to pass through the battery tray, circuit board and cover to fully capture and mount the assembly.  The design uses a Molex connector on the side to pass the wires through the side of the box. 

 

Below is the board installed on the side of the backup battery tray in the aluminum 3D printed box.  I will later wrap the Molex joint with silicone tape for a reasonable seal.

The circuit board is encased in acrylic to help protect it from moisture/oil.  Two additional wires were pulled through an existing firewall pass-through.  These wires were for the alternator (field) select line and  connection directly to the backup battery (to power the left EFIS and AHRS if needed and to monitor the backup battery voltage).  So a total of 5 wires go to the circuit board:  Backup battery, main battery, left SureFly, auxiliary power out for EFIS/AHRS and alternator select line.  All wires are fused nearest their sources of power as appropriate:  Three of the fuses are on the circuit board (backup battery, left SureFly and auxiliary power out), whereas the main battery wire is fused close to that battery and diodes current limit the alternator select line at the panel.

     

For my own reference, here is the pinout map for that box, looking in to airframe connector.

Since I have two alternators, I needed to create a circuit that allowed a line to go high any time either of the alternators were selected.  But also, it should only do that when the main bus voltage exceeds 13.7 V.  This is for redundancy in case the main backup battery controller board's Zener diode fails to a short.

This is a very simple circuit and is shown below.  The D4 LED (which is green) illuminates when either alternator is selected.  The D3 LED (which is red) illuminates only when an alternator is selected and the main bus voltage is greater than 13.7 V.  Thus each Zener diode (on this circuit board and the one explained earlier) "cover" for the other in case either fails to a short circuit. Verifying correct operation by viewing the LEDs has been added to my condition inspection.

I designed the circuit to plug in to the back of the alternator select switch (an Otto K1 model K1ABAPCABA) behind the panel so no wires need to be cut or spliced.  The back and front of the CAD models of the board are shown below (pictures of the actual board don't show the detail as well).  The side with female connectors plugs into the back of the panel switch.  The "ALT OUT" line goes to the backup battery circuit board to the corresponding location.

The EFIS and AHRS can be powered by the backup battery if necessary.  This allows me to power up the EFIS and AHRS before engine start and/or run the EFIS in flight if the main battery and two alternators become inoperable, understanding that the additional draw reduces the available flight time for the left SureFly.  It also allows me to monitor the backup battery voltage, giving me insight as to whether or not it's connected to the main bus (i.e., if the voltage is above its nominal 13.2 V, it's connected to the main bus) and if it isn't, what its loaded or unloaded voltage looks like.  

Adding the EFIS and AHRS to the backup battery places an additional 1.2 Ah load on the battery, giving the left SureFly, AHRS and EFIS a runtime of 1.5 hours under ideal conditions.  Again, switching off the EFIS and AHRS gives the SureFly more than 2x the runtime.  And since the backup Horis AI has its own independent backup battery, that possibly make the EFIS and AHRS unnecessary in an emergency.

To consolidate things, I wanted to use the existing switch on my panel that selects if the backup Kanardia Horis AI is connected to its own, independent, backup battery.  That battery is enabled when its input line goes to ground.  So a requisite circuit was designed with a PFET and isolating diode.

That circuit board was designed to plug in to the back of the Otto K1 switch (model K1AABPCAD) that enables the backup battery for the Horis AI.  When the backup battery switch is enabled, the Horis AI is connected to its own backup battery as usual, however the left EFIS and AHRS are then also connected to the EarthX backup battery.  However, the left EFIS and AHRS can still be isolated from both the main battery and backup battery through the use of the locking DPDT toggle switch (NKK Switches M2021LL3G01 with a red cap, AT427C) on the left side of the panel.  This allows the Horis AI to be enabled and the left EFIS and AHRS to be off if required.  

This shows the switch for the left EFIS.  In May 2025, I installed a similar switch for the right EFIS.   

The CAD models of the front and back of the circuit board discussed above are shown below.  The board includes provisions for fuses on the power output lines.  A high side PFET design is used for minimal loss when the circuit is enabled.

The left EFIS can then monitor the voltage of the backup battery and I also connected that power line to an analog input on the right EFIS so it too can monitor the voltage.  Thus, visual and aural anunciations are available if the backup battery voltage is below a programmed threshold and the backup battery voltage can be checked prior to engine start.

Screenshot from the right EFIS is shown below (immediately following a Vx climb, hence the OilT and CHTs).  The efficacy of the low R_DS PFETs in my design is apparent as the main bus and the backup battery are at the same voltage when the alternator is enabled and the main bus voltage is above 13.7 V.  Again, both EFISs are programmed to provide me a verbal and visible alert when the backup battery voltage indicates that it is disconnected from the main bus.

Finally, the aircraft's simplified high level electrical diagram now looks like the below.

Circuit boards parts list:

• Schottkey diode: Keyocera AVX SD1206S040S2R0
• PFET:  Infineon Technologies:  IPP120P04P4L03AKSA2
  
• Quick connect tabs, 0.25":  Keystone Electronics
• Male:  4902
• Female:  3528
• Resistor 10 k:  Panasonic Electronic Components ERJ-8GEYJ103V
• Resistor 1k:  Panasonic Electronic Components ERJ-8GEYJ102V
• Transistor:  onsemi MMBT2222ALT1G
• Zener 13 V:  Microchip Technology 2EZ13D5
• LEDs:  Lite-On, Inc.
• Red:  LTST-C150KRKT
• Green:   LTST-C150KGKT
• Fuse sockets: Keystone Electronics
• Black:  3568
• Red:  3568-10
• Yellow: 3568-20

 

Avionics: Mounted tablet for free charts via AvareX.

I mounted a tablet in the aircraft to avoid paying for charts and plates.  You can see it on the left in the image below.  Read on.

I had been using Seattle Avionics' charts on my GRT HXr EFISes.  I was disappointed to learn (during a checkride!) that some of Seattle Avionics' were not geo-referenced even though Garmin Pilot and AvareX have those same charts with geo-referencing.  I was further disappointed in how difficult it was to engage Seattle Avionics about this observation.  So I sought to find an alternative to Seattle Avionics.

With Seattle Avionics' charts on my EFIS, on the left below shows me running the KGLD VOR approach with the associated plate.  No purple plane, so not geo-referenced (and the yellow warning band on the bottom left of the chart).  On the right shows the RNAV RWY 30 approach plate during that same approach (a few button presses to switch between the plates), which is clearly geo-referenced.

Here's the KGLD VOR plate in AvareX showing aircraft position.  I believe they're able to geo-ref this plate because of the presence of known obstacles.  

Seattle Avionics eventually stated the following to me when I queried them on this concern:

This chart [KGLD VOR] is not geo-referenced because it cannot be.  To verify the geo-ref, we need at least 2 aviation points as cross-check or lat/lon lines or a line or ring with known distance.  That plate, like many VOR approaches, has just one point, so it cannot be verified, and therefore is not geo-referenced, as per DO-200B (SA is certified as such). 

Perhaps Seattle Avionics is limited in what it can do by some regulation in a way that AvareX would not be.  I don't claim to understand the details.

I had been using Avare and more recently, AvareX, on my phone when flying commercial, when on other GA flights or when flying on my couch.  So why not just use that in my own plane too? It doesn't require a subscription (though a donation to the software's authors is appreciated) and I have yet to see a chart that isn't geo-ref'd.

I bought a small-ish tablet, some mounts and snaked a USB cable over to the setup.  The further bonus is that this tablet can connect to my onboard Stratux and Virtual Radar Server to get live traffic plus access to aircraft registration data in flight.

I spec'd out some RAM mounts to use for the tablet and after going through a few different models, found what worked.  And it turns out that spacing between the screws on the RAM diamond base is very close to the spacing of the screws along the rail at the base of the canopy frame.  So I just drilled out one of the holes on the diamond base (to 1/4", IIRC) and mounted the base to the canopy frame.

In dutiful accommodating service to any passengers, I also snagged a phone mount for the passenger side.  I am open to later providing mixed nuts and a moist towelette.

Parts:

• Tablet
• Alldocube iPlay 50 Pro tablet 
• I do not use if for email or web surfing, so it uses a "burner" Google account.
• It's stuck using Android 14, which should be adequate for several years.  I've looked into if someone has successfully installed LineageOS on it.  I have yet to find a solid HOWTO for that.
• Case (not used in flight)
• RAM X-Grip universal holder for 7 -8" tablets with B-size ball, RAM-HOL-UN8BU
• RAM diamond ball base, B-size, RAM-B-238U
• Ram composite medium double socket arm, B-size, RAP-B-201U RAM. 
• Phone
• RAM X-Grip large phone holder with B-size ball, RAM-HOL-UN10BU
• RAM diamond ball base, B-size, RAM-B-238U
• Ram composite medium double socket arm, B-size, RAP-B-201U RAM. 
• Red rubber caps (to match the red motif of my interior)
• USB charging cables with power usage LED display 
• AvareX software
• git hub repository
• Google Play
• Apple App Store