Wind Direction in X-Plane (True vs. Magnetic)

[ChrisVon]

Hi All,

I'm wondering if anyone else shares my thoughts on the subject of wind direction, and how X-Plane implements it in the virtual world.

It's my understanding that wind direction is reported as relating to TRUE north, and that the pilot, in doing his flight planning, must take into account the magnetic variation when compensating for it's velocity in his wind correction angle calculations.

So here's what I'm observing in 10.40 beta 5. I set my plane at KLAX (Los Angeles Intl), and set the surface wind (or 2000 by default in the environmental parameters), to 270 degrees, with a (stiff) velocity of 20 knots. When I setup the data output for "Atmosphere: Weather" to display to the cockpit, I see the wind direction as being 281.8 degrees. With a magnetic variation of -11.83 degrees (as reported by X-Plane for that particular location), shouldn't the wind direction calculated by the simulator be 258 degrees (subtracting the 11.83 degree magnetic variation from the 270 degree TRUE wind direction).

I also took a Piper Cub, set it on the runway, and released the brake to allow it to "weather vane" into the wind. Again, I would have suspected my magnetic compass to show me pointed on a heading of 258 degrees. Instead, it points to 270 degrees (the TRUE direction that you set in the environmental parameters section in the sim).

I haven't been current in the real thing for some time, so my rationale might be off in this. But I reviewed a couple of King Schools DVD's about METAR decoding and Cross Country VFR planning and flying that BOTH say that wind direction is given in TRUE north direction, and, as stated above, the pilot must apply the correction himself to get magnetic.

None of this would concern most people if the only flying they do is through GPS or NAV radios, since the CDI would tell you in which direction and by how far off your course line you actually are. I prefer doing VFR flying "the old fashioned way", with a compass and stopwatch, and a flight log that I update passing over visual checkpoints, so a correct wind correction angle is a MUST, especially if I'm flying something as slow as a Cub (who's slow cruise speed EXACERBATES the problem of having a wrong wind calculation), with a wind / direction that requires a correction greater that 1 degree off the nose either direction.

I'm attaching a couple of screenshots to show you what I'm trying to convey, but please feel free to respond with another question of my (possible) flawed logic, or if you need more information.

Thanks!

Chris

Edited July 14, 2015 by ChrisVon

[philipp]

Suface winds are reported as MAGNETIC.

Winds aloft are reported as TRUE.

 

The reason is simply that runways are oriented to magnetic north. You expect the surface wind to be reported in the same way your runway heading is measured.

[ChrisVon]

http://www.met.tamu.edu/class/metar/quick-metar.html

[ChrisVon]

Actually, Philipp, as the link I pointed to suggests above, as well as a screenshot from the FAA's Advisory Circular entitled "Aviation Weather Services" that I'm providing in this post, a METAR wind observation is given in TRUE. But I approached this problem a different way. I reversed my thinking, and I now realize that what the user inputs in the environmental section of X-Plane is in actuality MAGNETIC wind direction. If you take that into account, then the wind direction that X-Plane is displaying in the data output is TRUE. This makes sense if you refer to my previous screenshots and pretend that the reported winds are 281 degrees at 20 knots. To obtain an accurate wind direction for the sim to apply to the environment, one must take 281 degrees, and ADD the magnetic variation to get 270 magnetic degrees. This of course is exactly what you do when you plot a course by hand on a sectional......

But here's where the REAL problem is I think: When X-Plane reads a METAR (real weather downloaded) report, it assumes that the wind in the METAR is MAGNETIC (as proven by the fact that my Piper Cub weather vaned into the wind and settled in the direction that the wind was input in the environmental parameters. In principle, what X-Plane is actually doing, is taking a TRUE wind direction provided by the METAR, and placing it in a field requiring a MAGNETIC direction. This isn't MUCH of a problem in areas (such as where I live), where magnetic variation is +/- 1 degree (in other words, the affect is negligable). But if X-Plane is reading a METAR with the assumption that wind direction is MAGNETIC, then flight planning (especially in-flight checkpoint recording), becomes problematic.

Until someone with more stroke than myself brings this to the development team's attention, the workaround is just not to use real weather, and manually enter the environmental parameters between weather reporting stations. (And yes, I submitted a bug report, but I don't anticipate much success with that.)

Edited July 16, 2015 by ChrisVon

[pots]

According to X-Plane 10.40 Beta 7 release notes from yesterday:

 

Bug Fixes

Fixes for Beta 7

• Metar wind headings now interpreted as true degrees

[Tom Knudsen]

Very int post, thank you for highlighting this issue

Member of: http://www.xpnorway.com Norwegian X-Plane Community

[Cameron]

Member of: http://www.xpnorway.comNorwegian X-Plane Community

 

Seriously dude? Your objective is so transparent right now. I don't care about the re-direction of traffic, but it feels pretty tacky to read a number of posts you have made in an aimless way just to try and gain some new traffic. 

[Tom Knudsen]

How could you say such Camron, and what's the difference from your signature besides you own the thing?

This is not even an effort to attract traffic, bet you there isnt that much norwegians in here anyway.

 

But by all means, show me the forum rules from signature content and I will remove it?

[Cameron]

How could you say such Camron, and what's the difference from your signature besides you own the thing?

 

Don't kid yourself Tom. That "signature" was in your post. Your signature is below it (this is where you tell me that was Tapatalk's fault).

 

 

 

This is not even an effort to attract traffic

 

I'm not stupid, Tom. It's insulting to everyone here for you to even try and play that card. You had absolutely ZERO interest in this topic since it's core discussion in July or any of the other few you posted in that don't even remotely sound like something you would normally post. You visit this forum near daily. If the post interested you, you would have responded weeks ago. I know you well enough to know what you typically post about, or how you reply. This is pure nonsense. Like I said, aimless posting.

 

 

 

But by all means, show me the forum rules from signature content and I will remove it?

 

Huh? Did I say anything about forum rules? I think I basically laughed at your attempt to be nonchalant. It's obvious what the motive was.

[Tom Knudsen]

Well this is stupid Cameron, why the sudden interest in just me? Is it because I speak out about shitty programs or do you have a personal agenda.

I am not trying to start an argument or getting any enemies. But i cannot understand why there is a what I call a which hunt to get me.

So who cares if I visit this forum once a day or twice a year, does it matter at all in this case? Does it even matter if you laugh at me? Think not but on that matter I do believe I have

earned the right to reply to your laughter.  (most likely should have this placed in the rant section, so excuse me for that )

 

That "signature" was in your post. Your signature is below it (this is where you tell me that was Tapatalk's fault).

 

 

I am not stupid neither are you Cameron, but I'm sure I did not post my signature in a post with intentions.

But for the sake of it, I will answer the next post on my cellphone just to see if there is a Talpatalk issue since I made the signature via that application.

So consider the next post a test post.

 

But If you are witch hunting me (a saying we use here in Norway when someone is out to get you) I hope you stop.

Said the same thing to Ben recently due to the fact It seems I have two nagging nellies commenting everything I do in this forum.

Ok by me, but curious to know if there is a reason for it or just for fun? Hell It could even be in my mind too

 

Anyway, Cameron, not my intentions be a jerk or even trolling this forum. I love X-Plane and flight simulation, it has been my number one interest for the past 18 years or so.

[Cameron]

Hell It could even be in my mind too

It's all in your head.

I stand by what I said with regards to your reason for posting. Deny all you want. It doesn't matter enough to change my mind.

The fact you even try to make up reasons why someone would ever come after you tells me you know someone may validly dislike you at some point though. If you have such feelings and can't take things dished out at you when you can be blunt yourself, I think it's time you re-think your approach with people.

For such a negative character at times you sure do have soft feelings.

[Tom Knudsen]

My feelings is not an issue Cameron, it is an persional opinion of others. In sense it is also boring and somewhat tedious. But you amuse me so I tend to listen to you. But this is getting boring Cameron, you failed to input some new arguments so I think this discussion is over. You have the rights to believe me or not, I really do not wast any calories on it. But if my signature is a violation of board rules, please let me know and and will remove it. I do not need to advertise for a norwegian community here, people will find it if they want to..

Member of: http://www.xpnorway.com Norwegian X-Plane Community

[Tom Knudsen]

You see, the signature input in talpatalk is replacing the "sent from my ... " just try it your self and see

Member of: http://www.xpnorway.com Norwegian X-Plane Community

[Cameron]

Remove the signature in Tapatalk. The forum will automatically apply the real one anyhow.

[Tom Knudsen]

Will do

[Keith Smith]

That's the most fiery debate about winds I've ever seen.

 

That aside, if it helps clear up the magnetic/true debate...METARs include true headings. Winds aloft are reported as true, too.

 

However, when the tower reads out surface winds, they are read in magnetic. This is because they're not reading the winds from the METAR, they're reading from equipment in the tower which is showing the winds in magnetic degrees.

 

Controllers on PilotEdge and VATSIM don't have such equipment. They DO read from the METAR and have to apply magnetic variation each time they issue the surface winds. So, if the METAR for LAX shows wind "26009KT", it would be read as "wind two fife zero at niner."

[stealthbob]

Controllers on PilotEdge and VATSIM don't have such equipment. They DO read from the METAR and have to apply magnetic variation each time they issue the surface winds. So, if the METAR for LAX shows wind "26009KT", it would be read as "wind two fife zero at niner."

 

 

That clears up an issue I was confused about, always thought I had different weather than what the PilotEdge controllers had.

 

I use the Wind data indicator panel in XPLane, I am going to assume that is True and not Magnetic?