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Is my Dynon Lying to Me?

ArVeeNiner

ArVeeNiner

Well Known Member
Something just ain't right here:

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I was flying directly toward the waypoint in both pictures. The Dynon is showing CRS, TRK, and GPS all essentially the same. The thing is, see the huge difference between the magnetic heading and the ground track? This is causing the Dynon to think that there is a huge crosswind when there isn't. I've calibrated the Dynon on a compass rose already.

I'm thinking there is a problem with my remote compass. Thoughts?
 
Has it ever worked correctly? If it used to work but has recently stopped, double check your compass settings for variation etc.

If it has never worked, then it might be due to where you placed it in the aircraft. Where is it located?

Beyond that, I don't know
 
I've had a somewhat similar problem with a Dynon D100 getting data from the Garmin 296. It lags the GPS by a lot, to the point where it's virtually worthless for heading information.

I too followed the instructions for calibrating mag heading (the one where you have to sacrifice a virgin on a compass rose) .
 
I only have about 15 flight hours on it and I would say it probably hasn't been right this entire time.

The remote compass is located high on an aluminum shelf behind the baggage area. I think a lot of builders put it there.
 
What magnetic fields do you have in this area? Elevator servo directly below? Do you have a rear-mounted battery and solenoid?
 
airguy said:
What magnetic fields do you have in this area? Elevator servo directly below? Do you have a rear-mounted battery and solenoid?
Click to expand...

No elevator servo or rear-mounted battery. I have the strobe box mounted on the side of the fuselage back there and the ELT as well. I haven't noticed any compass swings when I energize the strobes that I can recall but I'll look next time. These items are about 3 feet from the remote compass I would guess.
 
Was the compass rose used for calibration painted on top of reinforced concrete? This has been an issue with other folks....
 
Brantel said:
Was the compass rose used for calibration painted on top of reinforced concrete? This has been an issue with other folks....
Click to expand...

Hmmm, dunno but there is another airport near me with a rose that I plan to recalibrate it on.
 
A couple of comments. First, is that with the compass mounted in a magnetically clean area, and calibrated, it should be very accurate. And second, do you have a sliding canopy? If so, then you need to calibrate with the canopy slid forward. The frame of the canopy will magnetically interfere with the compass calibration when it is slid back.

-Robert
Dynon Marketing
 
When all else fails, check the obvious.

The slip indicator on your Trio indicates that you are flying with a lot of yaw.
this will cause your magnetic heading to disagree substantially with your ground track in zero wind situatons, thus indicating a crosswind.
 
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Vern: Good catch. However, the Trio is showing too much Right rudder, wouldn't that put the heading off to the right instead of the large left angle shown on the HSI? :confused:
 
DFlyer said:
A couple of comments. First, is that with the compass mounted in a magnetically clean area, and calibrated, it should be very accurate. And second, do you have a sliding canopy? If so, then you need to calibrate with the canopy slid forward. The frame of the canopy will magnetically interfere with the compass calibration when it is slid back.

-Robert
Dynon Marketing
Click to expand...

Yes, I do have a slider and I had the canopy open during the cal. I'll try it again with the canopy shut.
 
vlittle said:
When all else fails, check the obvious.

The slip indicator on your Trio indicates that you are flying with a lot of yaw.
this will cause your magnetic heading to disagree substantially with your ground track in zero wind situatons, thus indicating a crosswind.
Click to expand...

Yes Vern, that is a good catch. I've been working to get the plane to fly straight and obviously, I'm not quite done. However, I have stepped on the rudder pedal and it doesn't make a significant difference concerning the Dynon issue.
 
ArVeeNiner said:
Yes, I do have a slider and I had the canopy open during the cal. I'll try it again with the canopy shut.
Click to expand...
I am going to say this is your culprit. When you mounted the magnetometer in the location you chose did you take into consideration the slider frame? The slider frame is steal so if it is slid open and within close proximity to the magnetometer it will affect the reading. I bet you will see a difference when you recalibrate with the slider closed.
 
Is that wind vector on the Dynon correct (205-216 deg @ 68-72 mph) ? With that much wind you would have to have the aircraft pointed in that direction in order to track the course on the bug.
 
BillC said:
Is that wind vector on the Dynon correct (205-216 deg @ 68-72 mph) ? With that much wind you would have to have the aircraft pointed in that direction in order to track the course on the bug.
Click to expand...

No, that's exactly the issue.
 
ArVeeNiner said:
No, that's exactly the issue.
Click to expand...
The readout for wind speed will not be accurate if your magnetometer is not calibrated correctly. The calculations are using the magnetometer readings as one component of many in the formula. A small number variation from the magnetometer can cause a large deviation in wind speed numbers displayed. Do the re-calibration and test again.
 
RVbySDI said:
I am going to say this is your culprit. When you mounted the magnetometer in the location you chose did you take into consideration the slider frame? The slider frame is steal so if it is slid open and within close proximity to the magnetometer it will affect the reading. I bet you will see a difference when you recalibrate with the slider closed.
Click to expand...

I recall my roll bar being magnetized during the build. I degaussed it but I never checked the slider frame as I recall. My money is on the slider as well, Steve.

Thanks. I will perform a re-do soon.
 
DFlyer said:
A couple of comments. First, is that with the compass mounted in a magnetically clean area, and calibrated, it should be very accurate. And second, do you have a sliding canopy? If so, then you need to calibrate with the canopy slid forward. The frame of the canopy will magnetically interfere with the compass calibration when it is slid back.

-Robert
Dynon Marketing
Click to expand...

Robert

I think you're on to something here. I finally got out to the airport tonight and found out that the compass swings 30+ degrees between canopy open and closed!

Now I have to figure out how to keep my charts from blowing out when I fly with the canopy open! ;)
 
Just a follow up. I calibrated yesterday with the canopy closed and the crazy winds aloft have gone away! Who knew this would have an effect on the weather!!

Thanks for the help everybody.
 
compass check

For fun, grab a simple $2 compass and while holding it close to your plane do a 360 walk-around. You'll be amazed at how much needle deflection you'll get when passing by various steel components.
 
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