So what about that cable swap? Van's had released a notification on August 31st of 2012 that there was a wire swap in a conversion harness (for the ones that upgraded from a D180 system to a Skyview avionics system without swapping out the wiring). The wires of the secondary SV bus system connecting the two autopilot servos had to get "unswapped", so the backup bus system would function, in the unlikely event of the primary wiring failing.
I should add that although the backup wiring was always installed (and advertised by Dynon as a safety feature) it was actually never used in pre-4.0 versions of the firmware. The obvious problem of having the bus wires swapped (rendering the backup system compromised) was never detected before version 4.0 and before upgrading it was suggested to fix this issue.
That sounded easy enough.
All I had to do was to pull the Options harness plug and swap pins 3 and 4. It would have been quickly done but I had no means of testing that the swap was necessary or correctly done as my software version at the time of change was 3.3.2 and it did not use the backup wiring.
So I decided to first upgrade the SV display to the latest 6.0.0 firmware. And as all my previous experience with Dynon products, this was neither easy no very successful. No, it was rather frustrating again.
The first step was to grab the Dynon USB stick (4GB capacity) and copy the pure firmware update file on it (the one ending in .dub). The more modern update files with a .duc ending are not recognized by the old 3.3.2 firmware.
Now I did not delete the backup files and the 3.3.2 update files from the memory stick as I did not want to lose them.
Once I started the firmware update, I got to this screen:
This validation process appeared to take forever and no progress was seen. After more than 5 minutes, I ended up in the setup menu without any change. This update did not succeed. I tried a different memory stick (1GB with almost no free space left) and now saw an error message during validation, complaining that the update file might be corrupt.
I tried another, newer memory stick with 32GB capacity and practically empty and this time it worked. It appears that the SV system is using the memory stick for some temporary storage without saying so and not correctly complaining about too little free capacity. Great! That was the Bad - referring to the title.
Once all the external devices have been updated as well, SV reboots and comes up with these slightly modified screen.
As you can see, I still have not entered an activation key for the map yet. At least I started the process today and emailed Dynon my license key and my serial number.
Now, before I went to the Network Setup to see if the bus swap was necessary, I was eager to check if my display was affected by Dynon's Service Bulletin that indicated that a series of SVs had a board in them that was prone to failure due to a manufacturing process of a sub-contractor they had used. The setup showed that my system was in hardware group 1 which was not affected by this problem. That was the Good - in reference to the title of this article.
Now for the Network Setup and the check of the secondary bus system. Avionics and Autopilot switches were in the on-position.
So, it detected a connection fault (4/8 obviously indicates the secondary bus) but the system is operational. That seems to be consistent with a backup wiring failure. So, I turned the unit off, swapped the pins and powered the SV back up.
Huh? What is that?! Still two systems with a wiring fault???
A closer look revealed that now it showed a failure with the backup system of only one servo (which makes no sense as the servo connections are spliced and share the same bus harness and plugs) but now the ADAHRS has a problem with the backup system. How weird is that?
Now, to see if the swap of the pins really affected anything with the ADAHRS (I checked the wiring diagram and it should not do anything to anything but the two servos) I switched the servos off by turning off the Autopilot switch.
Just as I thought, the ADAHRS is fine and not affected by the wiring change. Once the servos are off, the problem with the ADAHRS disappears.
Well, if you are a long-time reader of this blog you will remember that I had a similar problem with the Dynon before. Actually, it was pretty much the very same problem, only that it affected the one and only primary bus system back then. The effect was that my ADAHRS was reporting just fine while the Autopilot was off but disappeared as soon as the servos had power. Initially both servos were working fine, a few hours into debugging the problem one servo stopped working, the other one was working fine and the ADAHRS was still dead as soon as the Autopilot switch was in the on-position.
After another dreadful experience with Dynon who replaced my brand-new servo with a refurbished one (but hey, it was free!) instead of another new one that would work, the problem was fixed. Or so it seemed until today.
My very strong guess is, that no-one ever checked the servos on their backup system and either the original servo or the refurbished one is now compromising the backup bus as soon as it comes online.
The one that is least accessible in the plane at this point is the roll servo, so I would guess that this is the one that is having the problem right now. The only sure way to find out is to get to the spade connectors and unhook one servo at the time and see which one makes the ADAHRS backup system disappear. That's the one that has the issue.
However, I am completely not in the right mindset to work on this POS again. Absolutely not in this heat and given that I have my experience with Dynon and know that their overwhelming helpfulness in this matter will possibly make me go postal.
For now I accept that I have a bug in the system that should get addressed but it is working right now and there is a safe way of getting the servos off the network and that is to cut their power supply with the autopilot switch. This is safe to get the bird flying. Once it is cooler, I can then crawl into the cone and see if my guess is right. So much for the Ugly in the title...
I continued to bring the SV system to the latest versions of the maps and data files.
I had bought a bunch of very nice antennas from Delta Pop Aviation. They are very well made and Don manufactures them himself and really knows what he is doing. They are not TSO'd but very affordable.
Here are the transponder and UAT antennas:
The UAT antenna is the one for the ADS-B receiver. You could use a transponder antenna but that is not optimal as the ADS-B frequency for the receiver is quite a bit lower than the one for the transponder and the signal will be weaker if you do not use an UAT antenna.
The additional transponder antenna will be connected to the PCAS and it should be as far away from the active transponder antenna of the RV-12 as possible.
I also manufactured two backplates for the small antennas:
I marked a good spot for the ADS-B antenna about a foot behind the aft bulkhead and close to the left side of the tailcone to keep it away from the cables in the cone and to increase the distance to the PCAS antenna which I will likely put on the opposite side.
The #8 is not a drill bit size but a screw size. These holes actually need a #19 drill bit and the center has to get opened to 1/2".
I will need a helping hand to hold the antenna in place while I attach the nuts on the studs from the inside, so I should try to get the installation of both antennas done at the same time. Also, I am out of star washers which I will need to put under the nuts.
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