Finding a place for a Dynon Skyview ADAHRS

[fellman]

Trying to find a location with minimum distortion of the magnetic field and still accessible for mounting, plumbing etc. First tried a location on top of the cockpit between the stringers planning to switch to stainless control cables but found out that the pilot/passenger headsets are real killers with strong magnetic fields. Now working on a location in the center of the back but getting quite big deviations of around 20 degrees on a compass and all a significant reduction of the magnetic field of some 20%. (same without the clecos visible in the picture).

Has anyone been through the same thing and what has been the solution? How much deviations can the Dynon calibration process absorb? The manual talks about "significant deviation" without telling what should be considered significant.

For those not familiar with the Dynon Skyview, the issue is that the magnetometer is part of the ADAHRS and not separate like with earlier Dynon applications or like Garmin and other brands where you put it out in a wing tip.

[kestrel]

I have an older D10A in mine. I installed the magnetometer outboard of the fuel tank, which has worked well. I have intentions of installing a Sky view. Since the pitot is out in the same place and I think it is within Dynon's allowed distance of the aircraft center for the inertial sensors, I was planning to put the Sky view sensor in the same place. -- Bearhawk

[fellman]

Thanks and good to hear kestrel. I looked at that but got turned off by the steel frame for the flap mechanism. You have to be quite close to that to be within the CG distance limitation but if your experience is that it works well it should be OK.

Have posted the same thing on Dynon's Skyview forum. Let's see if anything comes up there.

[kestrel]

Update/Correction: I double checked. I have my magnetometer one bay further out than where the strut attaches to the wing. Part of my access for mounting was the inspection hole/plate where the pulleys for the aileron are located. I reached in through the service hole and then then through the hole in the next rib out. That may be too far out for the Skyview sensors?

I need to bug Dynon about how they integrated all their sensors for the Skyview. It can be difficult to meet all the different requirements of each sensor type when they are all bundled together.

[fellman]

So, have learnt a bit more and posted the same question on the Dynon forum and turns out that the short answer is that Skyview cannot be made to work optimally on a tube and fabric fuselage like the Bearhawk. Either the compass will not be accurate enough with the ADAHRS in the fuselage or the attitude sensors will not work properly if you put the thing in the wing and it is too far away from the CG of the plane. The compass calibration function does not seem to be powerful enough for our type of aircraft.

The Skyview seems to be optimized for the RV market and planes with aluminium hulls.

Dynon is quite aware of this problem but does not commit to develop a version of Skyview with a separate compass that can be placed away from the fuselage like in a wing tip which is the usual location for most brands.

There are some quite bad horror stories out there where builders have bought the whole set up and then learnt that they will not be able to have a properly functioning set up and then ended up with poorly working compromises. The only advice from Dynon is to keep trying to find a location for the ADAHRS which is the best possible. Builders have used considerable time and effort but still without an optimal result. The problem is also that you want to decide on locations for the components and build brackets before covering the fuselage and closing the wings and that this means that you need to buy your avionics far in advance of what you would otherwise do in order to do as Dynon advises i.e. get into a process of trial and error. For many reasons, I do not think this is at all acceptable.

So, if you want to play it safe you have to go to one of Dynon's competitors. The only problem for me personally is that I think the Dynon Skyview suite is well set up for the experimental market and on the whole something I would like to have in my plane, so here is what I suggest:

If you are interested to consider Dynon Skyview a possibility for your own project, contact Dynon or your friendly Dynon dealer and make it clear to them that the present situation is not acceptable to you and that they are loosing a considerable chunk of the market unless they quickly come up with an option of a separate magnetometer for the Skyview. Of course, the more forcefully you make this point, the better it is.

This is a bit of a crusade from my side but I have already spent a considerable amount of time on the subject, researching, building different kinds of brackets, learning about magnetic fields and how to deflect them etc. By the way, there are some pretty cool iPhone apps to measure magnetic fields in three dimensions which is quite useful when you roll out your half built fuselage out of your shed and turn it around in different directions, measuring the interference from the Bearhawk frame and testing different bracket locations. This is all well but in the end you will need the actual Skyview unit to find out if the position is acceptable and the calibration will go through.

Happy lobbying,

Lars

[22LD]

Lars, this is all very interesting. My intent was to use the Skyview in my BH 4 place. Since reading this, I'm really considering just going with the Flight Deck 180 and add a Garmin 695/696. (And keep some of my money.) The other concern I have is the lack of a 4-place intercom. I've talked to Dynon about this several times but there doesn't seem to be any interest.

Also, doesn't the Garmin G3X Touch come with separate ADHRS and magnetometer?

[bestbearhawk1231]

22LD, the G3x and Touch version use separate ADHRS and magnetometers just like their certified EFISes do. Also, the big "G" follows certified industry standards for programing and wiring of their experimental avionics. What this means to the layperson is that if you are having trouble with the initial install or develop issues at an airport away from home it is easier to get help getting the issue resolved since any mechanic or avionics tech that is familiar with Garmin products can help you out. Wiring schematics, programming theory, and menu navigation are virtually identical to their certified family members. This also allows them to integrate seamlessly with certified components such as the popular all in one nav/com/gps boxes.

I have helped a friend install the skyview system into his Rans S-19 so I have read the manuals and agree that they system appears to be designed for aluminum hull aircraft. It is hard to argue with their thought process since the vast majority of homebuilts taking to the air lately are aluminum hull Van's and pop rivet planes. The fact that the skyview system does not have separate ADHRS or magnetometer made it a no go for me...that is a personal decision on my part. The skyview system is fantastic once it is wired and programed correctly. Getting there is another story that I will not get into. My background prior to my current job was Avionics on corporate jets, I expect install manuals and schematics to be laid out according to some kind of industry standard...especially when they want to play with the big names. I can open any install manual from the big "G" and have the system installed, programmed, and ready for flight test in no time flat because they follow industry standards. My experience with Dynon has not been as smooth, who knows, maybe they are following some kind of IT standard in their install manuals and schematics.

My intention with this response is not to start some kind of war between which avionics manufacturer is better but rather to give my opinion. I have worked with both systems and have my preference. I am sure the skyview system can be made to work with steel tube aircraft, but it makes me wonder why it would be used when there are systems out there that are designed to work with all aircraft. Realistically, when you pencil out the prices between all the systems and compare apples to apples, the prices are all within a $800-1000 of each other so why not simply use a system that is designed to be used with steel tube aircraft? If you have purchased your system already and it does not play friendly with steel tube fusalages, this is not designed to be a put down or cheap shot or anything along those lines.

[dedgemon]

Lars,
I have retro-fitted Skyview systems into 2 RV's by placing the ADHARS units in the wings. What I've done is attach the unit to an inspection plate with shims. Typically the issue with these situations is vibration of the skin. The vibration can bug the MEMS sensors. I've riveted an aluminum angle into the wing behind the ADHARS unit in order to stiffen the wing skin in the local area. The angle is tied into the 2 ribs with rivets and is also riveted onto the skin.

Now this works very well in the RV, but I've not tried it with a steel tube fuse. I would like to think that outboard of the fuel tank would be far enough, but I don't have experience or data to support that.

Good Luck.

[gseiter]

I just looked at the installation guide for the Skyview ADAHRS. It states it should be within 6' of CG laterally. Measured on my Bearhawk and found that to be inside the fuel tank bay. Drat! I was ready to take my panel to the avionics shop to have it built. Now back to the drawing board. Perhaps a Garmin G3X. I really liked the Skyview with all the plug and play options. Planned on a PS engineering 4 place intercom, everything else was going to be Dynon.

[Battson]

If you could find room - the front of the fuel tank bay would be a pretty good location. Perhaps inside the leading edge with a clever bracket?

There is very little volume of ferrous metal in that area of the wing, and importantly no moving ferrous metal parts. Wires could be routed elsewhere.

[Greg_Marlow]

I've got a Skyview in my rans S7S and it works fine.

[Zzz]

22LD, the G3x and Touch version use separate ADHRS and magnetometers just like their certified EFISes do. Also, the big "G" follows certified industry standards for programing and wiring of their experimental avionics. What this means to the layperson is that if you are having trouble with the initial install or develop issues at an airport away from home it is easier to get help getting the issue resolved since any mechanic or avionics tech that is familiar with Garmin products can help you out. Wiring schematics, programming theory, and menu navigation are virtually identical to their certified family members. This also allows them to integrate seamlessly with certified components such as the popular all in one nav/com/gps boxes.

This is great information! Haven't even starting looking at where to mount my sensors yet, but it's good to know this is a major consideration.

So the inertial attitude sensors are unaffected by the ferrous fuselage, it's just the magnetometer that must be relegated to the wing to reduce error?

Fellman, what is your plumbing back there? Is that pitot-static line?

[tailwind]

I can't speak about the Garmin touch, but I have the G3X. I mounted the ADHRS on the right side of the plane at the firewall. The only concern here is to have it oriented straight and level with the plane in flight. The magnetometer is mounted inside the right wing tip under the fiber glass tip. This installation seems to work very good. I especially like the on board weather. I also have a Dynon 10A as a back up. Garmin has been very supportive.

[bestbearhawk1231]

This is great information! Haven't even starting looking at where to mount my sensors yet, but it's good to know this is a major consideration.

So the inertial attitude sensors are unaffected by the ferrous fuselage, it's just the magnetometer that must be relegated to the wing to reduce error?

Fellman, what is your plumbing back there? Is that pitot-static line?

Zzz, the AHRS is not affected by steel however it must be mounted to a rigid structure within a certain number of feet of the center of gravity and must be within a couple degrees or so of level in flight. The box itself is not very big or heavy, they are usually mounted to the firewall or under floorboards. The magnetometer needs to be a certain number of feet from steel, fuel pumps, heated pitot tubes and electrical wiring. This is why they are normally mounted in the wings on aircraft. This is also why I am a strong advocate of running shielded twisted pair wiring to everything in the wings. When the shield is grounded, it prevents the magnetic fields that are created by moving electrons from affecting other wiring and components. This allows you to use wing tip lighting, aux fuel pumps, and heated pitot probes near your magnetometer. I am also a strong advocate of running 2 ground blocks on the firewall, one for all of your shield grounds and one for all of your power grounds then run separate cables to your battery. It takes a little more effort, time, and money doing it this way but you will be rewarded in the long run with a clean electrical system that is free from those electrical "gremlins" you hear people talk about. Also, you want to use brass or non magnetic stainless steel hardware to mount your magnetometer. Your install manual will give you the details on what is preferred.

[PaulD-Dynon]

If anyone on this thread is currently flying with SkyView, having compass issues, and willing to do some flight testing, Dynon would like to hear from you. We are working to better evaluate the issues surrounding magnetic compasses in steel tube aircraft. Please contact us at support@dynonavionics.com attention: Paul. Thanks!

Paul Dunscomb
VP Engineering
Dynon Avionics

[French]

Battson may be right for the location. On my Patrol wing, the only location that seems to satisfy the requirements is in front of the fuel tank, two or three rib bays outward.
There are a row of nutplates for the fuel tank cover, and tank straps. So, non-magnetic screws, and non-mag stainless steel tank straps ? If these can't be cancelled out
as non-dynamic magnetic sources in the Skyview, then there may not be a "clean" solution. Thanks to all for the good dialogue on this topic.

[fellman]

Just a note to let you know that I had a telecon with Paul at Dynon and turns out that they are taking this issue seriously and have a plan for solving the problem in the not too distant future. Paul is looking for someone who could do some testing for him as he mentions in his post above.
Anyway, my take from the conversation was that I will change my panel mock-up back to Skyview 😄

[kestrel]

You ask, Dynon delivers! ...remote mount magnetometer for Skyview. :-)