Are Foreflight’s wind crosswind direction arrows wrong?

[RobertE]

If you click on the runway tab in ForeFlight they spare you the mental math needed to estimate the headwind and crosswind components you will face upon landing using a given runway.  I must be overthinking things because it sure looks like the crosswind arrow routinely points the wrong way.

To give an example, when looking at Hailey, ID (KSUN) moments ago with a 9 knot wind from 320 the wind components for runway 31 showed an 8 knot arrow pointing down (makes sense since that’s the headwind component) but it shows a 1 knot crosswind arrow pointing from the left.  Shouldn’t that arrow point from the right since that’s where the crosswind will originate from?  What am I missing?

[carusoam]

Thinking along for a moment...  using logic...

Robert, I think I may have figured out your challenge... skip to step 7)

 

1) Wind arrows usually have a tail pointing towards the source and the arrowhead pointing in the direction it is going...

2) Your plane would point towards the source to maintained direction over the ground.....

3) So... a northerly wind arrow would point toward the south...

4) A X-wind would be broken into two vectors to describe the headwind part and the x-wind part...

5) The x-wind vector would have the tail pointing to the source (90° left or right of the runway) and the arrowhead toward the direction it is going across the runway...

6) your plane would be angled toward the tail to maintain direction along the runway center line...

7) So the runway heading is 310° Magnetic... and the wind is 320° True... You might be in the zone where true and magnetic might be causing calculation challenges with the scale of the magnetic vs. true shift?

8) winds are given in true north, not magnetic north for some reason.

9) What is the mag dev at your location?

How is that logic?

Does it agree or disagree with foreflight?

PP thoughts only, not a CFI.

Best regards,

-a-

[jasona900]

I pulled this from the Foreflight manual.  The manual reads as one would expect.  A crosswind from the left would have an arrow from the left and point to the right.  I looked at a few other airports around the country, and they appeared to be reporting correctly.  KSUN, as you stated, is reporting a left crosswind when it should be from the right.  Strange.

[RobertE]

How about that.  You guys figured it out.  Thanks.

[kortopates]

Yes, good lesson. Textual winds are always true north whereas over the ATIS they will be corrected to magnetic.
But 320 true = (320 - 13 east variation) = 307 magnetic winds vs runway 311 heading magnetic —> yielding 4 degrees from the left.


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