Wind Arrow Accuracy

[Rocketboy]

Hi,

Have done the MAGCAL stuff as close as I can and still have issues with the wind arrow. So far the best I can see is a 40 degree error (was 90 deg) as I fly the airplane thru different headings. What is the practical expected accuracy of this system?

Any tips or tweaks to improve accuracy?

Thanks,

Bob

 

[khorton]

Is it possible that the calculated TAS has some errors?  If so, that would affect the calculated wind.

TAS errors could be due to errors in the indicated airspeed, or OAT errors (although it would take a very large OAT error to create a 40 degree wind error).

It might be useful to fly a four leg box pattern, with the same IAS and altitude on each leg, and note the GPS track and ground speed and Dynon TAS for each leg of the box.  The exact difference in tracks or headings between the four legs is not critical, as long as the aircraft is nicely stabilized at the target IAS and altitude and on a constant track when you take the data on each leg.  Then either use the four leg option on the NTPS GPS to TAS spreadsheet, or send me the data, to get the TAS.

 

[Rocketboy]

Yes, TAS is low. what kind of consistancy do you get around a 360 deg heading change?


bob

 

[dynonsupport]

Most customers get 1-3 degrees of accuracy at all headings. If you can't get better than 40 degrees, there's an install problem or a hardware issue.

First question: Is this a D10A with an internal compass? If so, most customers can't get a good cal with this due to all the other stuff in the panel. It's the reason we came out with the remote compass.

If it's a D10A w/remote compass or a D100/D180, then the question becomes where is the EDC and is it installed correctly. Tabs down, D-9 connector pointed forward? Totally away from any ferrous metal and any wires with real power in them?

 

[Rocketboy]

Hi,

Its a 180 with EDC in the tail. I going to check to make sure it's parallel with the 180. Thats the only potential error I can see.


Thanks for the help.

Bob

 

[dynonsupport]

Is it near any powered object, or electrical wires? And is it away from any ferrous metal like steel?

Also, confirm that the EDC-D10A is mounted with the tabs down and the connector forward.

 

[Rocketboy]

Yep to all, about 18 inches from steel tubing in canopy frame.

will check EDC angles tomorrow.

Thanks,

Bob

 

[dynonsupport]

Additionally, to see if the EDC location is being adversely affected by surrounding metal/power - simply hold a boy scout compass up next to it and see if it reports the same incorrect heading. If it does, no amount of calibrating make the compass perform better in that location.

 

[Etienne]

Additionally, to see if the EDC location is being adversely affected by surrounding metal/power - simply hold a boy scout compass up next to it and see if it reports the same incorrect heading. If it does, no amount of calibrating make the compass perform better in that location.

But remember that when you stick the boy scout compass near the EDC, the EDC will go haywire... Make sure that the compass is on the other side of the planet before comparing the scout compass reading to the EDC's reading!

 

[vlittle]

In my opinion (and was discussed about a year on airspeed calibration), any static position error or instrument error in the D10A can lead to large variation in the wind arrow.

For example, my D10A reads about 4% low in my RV-9A. Therefore, at 100 KTAS (104Kt ground speed) with a 4 knot cross wind from 090, the wind arrow would indicate about 6 knots from 045.

If you turn 180 degrees, the wind arrow would indicate 6 knots from 135.

Conclusion: when the magnitude of the crosswind is comparable to your known airspeed error, the wind arrow vector is not to be relied upon.

I was hoping at one time for Dynon to allow a correction table for airspeed, but I don't know if that's in the development plan.

Vern Little RV9A