Replaced ADS-B Module and Wrapped Up Maintenance

I wrapped up the heater valve swap by reconnecting the SCAT tubing and control cable and then reinstalled all of the interior aluminum covers and seat pans. Before reinstalling the cowl, I checked the breather vacuum valve in case I needed to clean it. I’ve been checking this every oil change and it never seems to get worse than this.

Before reinstalling the interior, I needed to swap the ADS-B module. Dynon recently contacted me about swapping this because they apparently found a hardware defect and they want to replace all of the units in the field. Although I don’t relish removing all of the interior and baggage wall to get to this, I don’t mind since I really appreciate how proactive Dynon is about resolving issues like this.

The new unit is identical from the outside, so it’s a trivial swap (unlike when I swapped from the SV-ADSB-470 to the SV-ADSB-472).

Added Auto-Trim to the Autopilot

Dynon released version 12 of their software which adds auto-trim to their autopilot. To enable this, I needed to rewire the trim to go through the Dynon Autopilot Control Panel instead of through the Vertical Power VP-X. This entailed several hours of laying on my back under the panel rerouting wires.

The Autopilot Control Panel needed power and ground to run the trim servos. Fortunately, I still had a few extra power pins on the VP-X, so that was a quick addition. I then needed to reroute the four wires from the trim switch and the two pairs of wires to the pitch and roll trim motors. These eight wires all had d-sub pins or sockets, so I built a new harness that extended the wires from this point.

After finishing up the rewiring and upgrading the software, I ran the trim calibration routine and then flew Jenn to lunch in Half Moon Bay to test it out. The auto-trim worked great and kept the plane in trim the whole flight.

Finished New Avionics Installation

I stopped down at the airport with the kids and wrapped up the new avionics installation.  All that was left was installing the nutplates and doing the wiring.  I previously just had a single network cable connecting the two displays, but I needed to replace that with three network cables (left SkyView to knob panel, knob panel to autopilot panel and autopilot panel to right SkyView).  Since I had run the previous network cable between the two screens along the sub panel, it was long enough to cut and install new connectors on to make two of the three cables I needed.  Fortunately, I had enough scrap network cable in my box of wires to make the third.

After hooking everything up, I did a network config to allow the SkyView system to find the new boxes and did some ground tests to make sure everything was working properly.  Since I had the kids with me, I couldn’t take it up for a test flight, but I’m sure these will be a nice improvement to the panel.

Test Fit New Avionics

I cut the holes for the new avionics boxes and test fit them into the holes.  Cutting these holes in place was a real pain.  The nibbler I had wouldn’t cut 0.063″ thick sheet, and I didn’t have anything else that would work well.  I ended up drilling a series of 1/4″ holes around the perimeter and using a file to open the hole up enough for the avionics to fit.  It was quite a bit of iteration and it ended up taking me nearly 2 hours to get them cut.  That was still way faster than pulling the panel out of the plane though.  With everything installed and aligned, I drilled the mounting holes through the holes in the face of the avionics.

Afterward, I pulled the new boxes and the GTN, then used a scrap miniature #6 nutplate to drill holes for the rivets that will hold the nutplates in place.  I still need to countersink the holes and rivet them in place, but I’m beat tonight.  It shouldn’t take more than a couple more hours to finish up the nutplates and then fabricate a few new network cables to tie the boxes together.  The autopilot control box (on the right in the picture above) also includes a trim controller that essentially does the same function as the VP-X that controls the trim now.  In the future though, Dynon plans to add auto-trim to their autopilot, so I’ll eventually rewire the trim to go through this box.

Final Wheel Pant Alignment and New Avionics

I put the plane back up on jacks and slowly enlarged the mounting holes up to #19 for a #8 screw while adjusting the wheel pants to be perfectly aligned with the longitudinal axis of the plane.  They were off a little bit when I started which is probably due to the epoxy/flox shims slightly shifting the position of the pants from when I first drilled them.  Since my brackets are stainless steel, I needed to use a fair amount of pressure to drill these, so I backed them up with some wood to prevent them from flexing in as I drilled.

After drilling these out, I pulled the wheel pants and gear leg fairings off the plane and to the plane back off the jacks so it’s ready for flight again.

Dynon recently released two new boxes that work with the SkyView system: one to provide dedicated knobs to control the altitude bug, heading/track bug and barometric pressure and another to provide a set of dedicated autopilot controls so that you don’t have to navigate through various menus to control it.  I’m mounting these in my radio stack with the outer edges flush with the other boxes in the stack.  This leaves enough room in the center for another small device if I want to add one.  I laid out for the holes, but it was too late to start cutting into the panel.  Once I have these mounted, hooking them up to the SkyView network will be pretty straightforward since I can just daisy chain them between the displays.

Adjusted ADAHRS

The inclinometer on my SkyView has always shown nearly 1/2 ball out to the left, even when the fuselage was absolutely level.  After doing some research, it looked like the only way to adjust this was to shim the ADAHRS until in showed a centered ball with the fuselage level.  I used my shop crane to raise the tail to a level attitude and put my aircraft jacks under the jacking points on the wings to hold the plane rigid in the roll axis and to make minute adjustments to the lateral level of the plane.

After getting the longerons level, I used the wing jacks to adjust the lateral angle until my digital level showed 0.0 when placed across the seat back support.  I then zeroed the smaller digital level I have and placed it on the ADAHRS.  Sure enough, it showed about 0.5º angle with the left edge low (exactly as a left ball would indicate).

I removed the attachment screws holding down the ADAHRS and fabricated some small aluminum shims to fit under the left edge.  After some experimentation, I found that I needed a 0.048″ thick shim to center the ball.  Now the ball is nearly perfectly centered.  I’m really surprised how sensitive this is.  Varying the shim thickness by just a few thousandths made a visible difference in the position of the ball.  Given that my digital angle is only accurate to 0.1º, it’s really hard to get this accurate since I can now move the ball from one vertical mark to the other while still reading 0.0º on my digital level.

While I had the plane in the level attitude, I was curious how much ground clearance I have from the propeller tip.  This is the best case without any further gear compression.  If I were to bounce a wheel landing or raise the tail too far, this clearance could diminish significantly.

Greg also stopped by with his Windows laptop so we could make a few adjustments to my VP-X.  My Windows laptop is acting up (surprise, surprise), so I haven’t been able to use it to connect.  We configured the Wig-Wag function, set up intermediate stops on the flaps (and configured the VP-X to use them instead of requiring me to hold the flap switch until they reach the position I want), and turned off current monitoring on the fuel pump.  I still need to adjust the flap airspeeds, but I forgot at the time.

SkyView Battery Test, Bowden Clamps and Fuel Filter Servicing

I previously sent the backup battery from my left SkyView screen into Dynon because it didn’t seem to be charging during the first few flights.  They charged the battery and tested it and it was fine.  They sent it back to me so I installed it tonight and ran the battery test on both screens.  Both passed by powering the screens for 45 minutes (and new batteries should power the screens for more than 1 hour).

While the battery test was running, I replaced a couple of cable clamps in the engine compartment with non-cushion bowden clamps that hold the cable much more securely than the cushion clamps I was using before.  This is the clamp for the oil cooler butterfly control cable.

I also replaced the cable clamp at the forward end of the alternate air door control cable.

Finally, I decided to pull and clean the fuel filter again.  There was a surprising amount of gunk in the filter.  Most of the volume was some sort of fuzzy material, but there was also a lot of dust and even one small metal particle.  I redid the safety wire and installed it back in the airplane.


I met with the DAR this morning.  After he inspected the plane, we went over the paperwork I submitted and then reviewed my operating limitations.  Finally, he issued my airworthiness certificate, so the plane is officially airworthy.  We spent a little time afterward discussing my preparations for flight testing and covering the test plan for my initial flight.

My airframe logbook also gets an entry stating the plane is airworthy.

With the final inspection done, I started buttoning up the plane to get it ready for flight.  First up, I installed the wing inspection panels (all but one which I’ll discuss below).

I then moved on and installed the wing root fairings.  The adhesive I applied the other day seems to have worked out well.

Before installing the last wing inspection panel, I needed to install the aileron servo stop.  I couldn’t get the bracket in place without enlarging the center slot a bit.  After ensuring it would fit, I shot a fresh coat of paint on to keep this from rusting.

Finally, I installed it on the servo.  Slipping it behind the arm and under the safety wire is a little tricky and it will only go one way.  I installed an AN960-10 washer between the bracket and the servo under each mounting screw to space the bracket away from the servo by the thickness of the servo mounting bracket.

Update: I subsequently caught that the safety wire on the lower bracket bolt was reversed.  This is another issue that I’m surprised wasn’t caught at the builder inspection party.  There wasn’t much room to work in there, but I managed to get the wire reversed.

While doing a thorough pre-flight before buttoning up each panel, I found this missing bolt (you can see the bolt over on the right).  I had removed this a long time ago because I was using it to hold an adel clamp for the servo wires.  When I rerouted the wires, it never occurred to me to check this.  I’m really surprised that this wasn’t found during my builder inspection party.  There were a couple of guys that were doing a pretty thorough inspection with mirrors and flashlights.  Regardless, I had always planned on doing a complete control integrity check from end to end, so I wouldn’t have made it to first flight without catching this.

I installed a new bolt (and way too much torque seal because I couldn’t see it well).

With nothing left to do on top of the engine, I installed the plenum for the last time before first flight.

I also installed the spinner.

Since I need to shift the alternator back by about 3/32″, I pulled the mounting bolts and removed it.

I’ll need to file off the aft end of the pivot shaft (not visible here), I taped up the alternator to ensure no metal filings make their way inside.

This shaft is about 2.992″ long, and I need to take about 0.094 off the right end of this shaft.

I can then use one AN960-616 and one AN960-616L washer to make up the difference.

After grinding down the shaft, you can see that I have the same length when I now include the washers.  I’ll reinstall the alternator tomorrow and re-tension the belt.  This ended up being way easier than I expected.

Calibrated Fuel Tank Senders

I calibrated the fuel tank senders today.  I’m using the Princeton two-point capacitive senders which are pretty straightforward to calibrate.  Here are the basic steps:

  1. Empty the tank (I had already done this when determining unusable fuel for the W&B).
  2. Power on the sender.
  3. Hit the set button to set the empty point.
  4. Fill the tank.
  5. Hit the set button again to set the full point.

The sender then puts out the full 0-5V range from empty to full.  This is much better than the Dynon capacitive senders which can’t be calibrated and generally put out a small fraction of that voltage range across the whole tank capacity.  The Princeton senders solve the dynamic range problem, but the voltage still doesn’t necessarily follow the fuel volume in a linear way.  The SkyView system solves that by including a separate calibration mechanism where you add fuel 2 gallons at a time.  Each time fuel is added, a button is hit on the SkyView to correlate that particular voltage reading from the sender with that fuel volume.  Unfortunately, this means that I need to start over with an empty tank to do the SkyView calibration.  Since I don’t have any interest in draining that much fuel out of the tanks, I’ll have to wait until I’m flying and can burn down the fuel.

I did this for the left tank by pouring fuel from gas cans into the tank, but it was very time consuming and I ended up spilling some gas.  Since I hadn’t run the engine in a month, I taxied the plane down to the pump to calibrate the right tank.  I used that as an opportunity to break in the brakes a bit more too.

Using the capacitive probes with the Princeton senders should result in a nearly perfectly linear fuel gauge reading across the entire tank capacity.  This is quite a bit better than the resistive senders which read empty when there is still a fair amount of fuel in the tanks and reads full well below the full capacity of the tank…