In Flight Wind speed off by 30 kts.

[kurtfly]

I noticed on my last two flights the Dynon Skyview wind speed is off by ~25 to 30 kts.  The wind direction is correct as I compare it to the D-100 and the GNS430W.  I used to see all 3 be reasonably close to each other with the GNS430W exact same as Skyview.  Does the GNS430W not get all the required info from Skyview, ie: temp, IAS, heading...????  If so, why would skyview display any difference?  This was a very calm day.

I am flying a Glasair S II-RG, Dynon D1000T, Dual ADAHRS, GNS430W, D100.

All other aspects of the Skyview appear normal.

I have attached 3 photo's of my display's.  all 3 were taking within seconds of each other.

 

[kurtfly]

I have some additional info that makes me believe this is a Dynon GPS issue. Perhaps related to the GPS time missing (parsing issue) on older GPS250 pucks.

When I view the GPS Course on the GNS430W or my GPS250XL they agree with each other but the Skyview GPS Course is different; to the right, by 7~10 degrees.
To further illustrate this while on the ground lined up with runway (slow taxi) the MAG headings (SV and D100), and GNS 430W GPS Course all match (within 1 degree). SkyView also shows on Map page the course of the same but it is in a white box. Once I taxi to > 20 kts the SV GPS Course jumps 7~8 degrees to the right, the MAP Course is now outlined in Magenta. I believe the magenta indicates the course indicator transitioned from heading to GPS Course.

While in flight I see a consistent difference between SV Course and my other 2 Garmin GPS's.
Dynon - can you explain? Is this related to the UTC Time display parsing issue? My GPS 250 was purchased on 4/22/2014. No serial number.

Thanks,

Kurt

 

[CGameProgrammer]

The same thing happens to me. Unlike your ridiculously fast aircraft I tend to fly at 85 knots indicated but the wind indicator will often indicate a wind of 20-30 knots even when I'm only 1000 AGL and every airport's ATIS is reporting 5 knots.

 

[akarmy]

one thing to check is that your compass calibration is correct. We've noticed similar readings on 2 planes locally and it ended up being a compass calibration error. In one case the compass rose being used to calibrate was actually painted wrong (it aligned to true north, not magnetic north)

Just something to verify.

 

[dlloyd]

Agree with Andy. If the compass calibration was not done or done properly, wind estimates will be incorrect. You are showing on the Skyview a ground track of 111 and a heading of 101. It would take 31 knots crosswind to do that when flying 180 knots, not 6 knots as your D100 shows.

 

[kurtfly]

I would agree with you except why does the GNS430W show different from SV by 28kts? All the data is from same source( Skyview) except the GPS course. Why does the GNS430W gps course and the GNC250XL GPS course differ from SV GPS course by 7 degrees?
Before about 2 weeks ago the GNS430W and SV showed the exact same.
Now there is a significant difference between them.

Kurt

 

[kurtfly]

Based on another post regarding the "GPS250 missing time" I downloaded my User Data Files. I see the "Unknown Time" in the GPS Date & Time column. I am convinced my problem is associated with the needed GPS250 software update.

Dynon? What do you think?

Kurt

 

[Dynon]

Yes, the GPS time problem causes SkyView's magnetic variation to be computed incorrectly, which causes winds aloft issues.

 

[bobl_51]

Is this fixed in 15.3.5? Is it a hardware or software problem?
This first showed up for me mid April - crosswind vectors of 40-50+ kts. I was on 15.3.3. I redid the Skyview compass swing a couple of times, thinking that it has to be that. But my magnetic compass agrees with the Skyview compass. Redid the in-air compass calibration a couple of times too.  I was just planning to use the compass rose at another airport (what else could it be?) before calling Dynon in frustration...

I just checked my data logs - my last few flights are showing UNKNOWN_DATE_TIME for the GPS Date&Time. It is still showing UNKNOWN_DATE_TIME with 15.3.5, but the heading sitting on the ground is now 20 degrees off my magnetic compass.

What should I do?

 

[kurtfly]

You need to contact Dynon Support. They will send you a link to Version 15.4.3 that will correct the GPS issue. It should correct your "Unknown Time" and the GPS Course (Winds aloft) issue.

Kurt

 

[kurtfly]

I loaded 15.4.3 Software and flew this evening.
It corrected the GPS Course and the Winds Aloft calculation, However, logfiles still show "Unknown_Date_Time" in the GPS Date & Time column.

Dynon will have to answer this one?

 

[djones]

So it looks like there is another layer to this GPS onion. Engineering is looking into it, but it may be a few days
before we have an answer.

 

[kurtfly]

Let me know if you need me to send a diag. dump file?

Kurt

 

[cmgolden]

I also have "UNKNOWN_DATE_TIME" in my logs. Version 15.4.3.

 

[kurtfly]

I just flew with 15.4.4 and it corrected the "Unknown Date & Time" in the user logs and the GPS Course / Winds aloft bad calculation.

Thanks,

Kurt