dynon skyview wind speeds way off and mismatched on each screen

[david.perl]

Ive recently noticed the skyview wind speeds are over reading by anything upto 20 knts and are different on each display. If I swap screens, the error does not swap over, it stays on that side.

Ive got dual ADHARs and both read the same inflight

Ive done an inflight compass calibration and get over 100 and that's made it slightly better.

I plan on doing another ground compass swing, however that won't explain the mismatched screen readings.

any ideas out there?

Ive also noticed the skyview forum that Dynon run has server issues and is not running.

[RBR]

I popped on here today to ask virtually the same question and saw your question David and I thought I might piggyback on your thread.

I only have a single ADHARs unit but when doing the GPS boxes again yesterday I find the Dynon winds on the cardinal headings are:

090: 130/18
360: 101/19
270: 094/21
180: 139/08

The expected 2000' W/V from the Met Bureau was 130/11, the GPS box wind computation was 111/13.

I flew the GPS boxes again as my TAS readings were consistently 4-5kts high. In dialing out what was likely a static position error, I changed the static ports from Safe Air to Cleaveland. I now read 1 kt high, so I am very happy with that. But the displayed winds are still off.

I have also just conducted a compass swing using an external aviation compass. Some of my original headings were up to 2 degrees out. Like you, I then did an airborne swing and got a Skyview figure of merit of 136.

Hopefully someone may be able to steer both of us in the right direction. I would have posted on the Dynon forums, but they are still down.

[Timberwolf]

If your magnetometer is off it will affect winds. Not too familiar with the dynon in this regard but if you can recalibrate that it will probably bring them back in line.

[bugsy63]

G'day Guys

I had a mismatch between screens but I only noticed the time not being displayed on the Primary Screen. The fault also stayed on the PFD when swapped.

Mine appears to have been related to the GPS roll over issue in April. I installed the latest software and it rectified.

Regards

[Skysailor]

Check to see if one of your screens is affected by the GPS week rollover issue. This is confined to Skyview displays utilizing the GPS250 antenna with a manufacture date prior to 2013. GPS2020 antennas are not affected. It will cause incorrect magnetic variation to be used which could lead to large errors depending on location. There is a software fix for it which Dynon will provide.

[Norman CYYJ]

Winds aloft calculations are only accurate on any system if flown straight and level. They don't show properly while in turns.

[Rainier Lamers]

The calculations are based on the common wind triangle formulas you learned for you pilots licence. No magic here.

You need 4 numbers:

Ground speed and true ground track from the GPS (That's not a problem).
Then you need true airspeed (usually some small errors here).
Then you need magnetic track corrected for local variation. This comes from your compass/magnetometer and this is where things tend to go wrong.

This has to be accurate. The formula needs to know which way your aircraft is pointing vs which way it is traveling over ground. That gives it an idea of the strength of any wind from the side and which side.
The difference in speeds effectively tell the formula is the wind comes from the front or rear.

Feed all this into the formula and out pops accurate wind speed and wind direction provided everything is measured accurately.

As pointed out - it only works if you are flying straight and level (no slip, no turn) as only then can we have an accurate angle between ground track and heading.

As with anything - rubbish into the formula - rubbish out...

The compass/magnetometer location or calibration is the usual culprit if rubbish comes out...

Rainier
CEO MGL Avionics

[RBR]

Thanks Rainier.

I'll look at my ADAHRS installation again as the other aspects you mention have recently been investigated.