Any other SV users having Wind Vector errors?

[k.gregory]

My SkyView system always shows me with a tailwind of varying degrees. This appears to be caused by small errors in both the IAS and compass heading information. I've done some testing that shows Indicated TAS is 7 to 9 knots slower than actual. The wind vector is all over the clock. The GS runs data are listed below.
Do any of you know how to correct this?



IAS/Hdg/TAS error: Ground Speed averages at 8000 feet MSL, OAT 15 degrees C.

KIAS GS iTAS RPM GPH Wind
South 138 159 160 2870 7.4 090 at 11
North 138 173 160 2880 7.3 180 at 14
Computed TAS: 166

East 139 164 160 2880 7.3 315 at 9
West 138 174 160 2890 7.2 045 at 14
Computed TAS: 169
Computed KTAS all legs: 167.5

 

[dynonsupport]

The first thing you need to do is a pitot and static check to make sure you have no leaks and the AHRS is reading your speed right. The AHRS is calibrated here and failures that lead to small errors are very rare, but it could happen.

Accurate heading is critical to winds as well.

Finally, the proper way to test for airspeed errors and canceling out winds is actually a triangle, not just the average of 4 directions.

http://www.kilohotel.com/rv8/article.php?story=Kitplanes_You_Know_Yo_Pitot

 

[eric.reed]

You might also try to see if the airspeed errors appear consistent at varying indicated airspeeds.

It is possible that the static port could be seeing a slight increase over ambient pressure due to its position. This could vary with indicated airspeed. You may also notice GPS altitude is consistently a bit higher than baro altitude if this is the case. If anything like this is happening, then the pitot/static check would not show it.

Based on the information posted, a 7 knot error in the indicated airspeed along with small errors in the compass tending to pull it towards north would make sense.

Regards,
Eric

 

[GalinHdz]

You might also try to see if the airspeed errors appear consistent at varying indicated airspeeds.

It is possible that the static port could be seeing a slight increase over ambient pressure due to its position. This could vary with indicated airspeed. You may also notice GPS altitude is consistently a bit higher than baro altitude if this is the case. If anything like this is happening, then the pitot/static check would not show it.

Based on the information posted, a 7 knot error in the indicated airspeed along with small errors in the compass tending to pull it towards north would make sense.

Regards,
Eric

I had this exact issue where the error(s) became greater as my airspeed increased. TAS, altitude and wind vectors were all off as my airspeed increased. The Skyview was dead on, but my static port was in an area of increasing low pressure as airspeed increased. Was not an issue at a slower airspeed but significant once my airspeed went beyond 150KTAS. I corrected the static port problem and the system is well within 1KTAS for the entire range of airspeeds.