Winds aloft issue (vid)

[znurtdog]

Flew with autopilot making 90 degree turns to see how the winds aloft reported. Let me know what you think. Thinking airplane's pitot install might be off? This is a factory built Czech Sport Cruiser. https://youtu.be/bYELsQvY3zE

 

[dlloyd]

Has your compass been calibrated? That could cause the problem.
Is your airspeed accurate? That could cause the problem.
One, the other, both.

 

[Dynon]

dlloyd basically has it right. If your compass calibration isn't excellent, you'll have issues in both magnitude and direction of the winds aloft. You can compare on the ground against either a known good location (compass rose), or on the roll by using GPS ground track. When you taxi straight ahead, track and heading should be the same.

Similarly, if your IAS indication isn't actually your IAS, you can also see both magnitude and direction issues. Issues of this nature are usually due to the pitot/static design, and more often than not it's the static port not really being static in flight (although it can be the pitot as well).

 

[lolachampcar]

It took a bit of effort to get my IAS correct. Specifically, my Static port is just behind the Pitot and IOA ports on my plane making static pressure air speed dependent (not good). I ended up doing a simple test to identify then trim out the issue. I found a long run way, lifted off then maintained a set height above the run way as the plane gained speed. If you log data through this process, you can identify static sensitivities as altitude should not be changing with air speed. It took about three passes of adjusting the thickness and relative location of some shrink tubing on the probe and I had altitude dead flat over a 100 nt/hr change is air speed. My winds aloft have been accurate ever since.