Sign in to follow this  
Sportsfan23

Can someone explain how surface winds are calculated?

Recommended Posts

I just did a short flight from KPHX to KLAS. Before leaving KPHX I checked ASN and it said the winds were 250/6 at KLAS so I figured I would be landing on 25R. Anyway as I got close to approach I tuned the radio to KLAS and it said the winds were 238/6 which still seemed like 25R would be the right choice. However on approach the winds were 028/12 or something close to that. Why would the winds be so different from what was said on the radio and in ASN? 

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

It's unusual for the winds to shift that much but real crews are often faced with non optimal winds. For example it would be better to take a small tailwind onto an ILS equipped runway rather than a complicated NDB or other non precision procedure just to get a headwind.

 

In terms of what happened to you, it's likely to be a glitch in the weather engine.

Share this post


Link to post
Share on other sites

1. It's not a glitch in the weather engine.

 

2. It can be the way FSX processes data as you are descending. Sometimes it can read the data at your current altitude, sometimes it can read the surface winds. Use the FlightWatch audio in ASN to be sure.

Share this post


Link to post
Share on other sites

Also important to point out that METAR winds are in true, ATIS (radio) winds are magnetic, hence the slight difference between the two.

 

I'm not sure why your winds are so far out...I was initially thinking it may be due to orographic lift (which ASN simulates), but that usually affects wind speeds and not so much direction...not as much as yours anyway.

 

If you keep encountering this, you will want to open a ticket at hifisim so Damian or Kostas can see if or what the problem is.

Share this post


Link to post
Share on other sites

In older versions of Active Sky, when using Global weather mode, there was a problem with FSX ATC using the winds at your current position and altitude, not the destination surface winds, and that would lead to FSX ATC being completely useless for approach and landing.   I thought they fixed this in ASN so that stock FSX ATIS and the approach controller should now use the actual runway surface winds.

Share this post


Link to post
Share on other sites

In older versions of Active Sky, when using Global weather mode, there was a problem with FSX ATC using the winds at your current position and altitude, not the destination surface winds, and that would lead to FSX ATC being completely useless for approach and landing.   I thought they fixed this in ASN so that stock FSX ATIS and the approach controller should now use the actual runway surface winds.

 

It has been fixed in ASN...mine is bang on and stable every time.  That's why I suggested if this is a recurring problem with his setup that he create a support ticket at hifisim.  It may have something to do with with how the AS modules are connecting...something may be blocking them.

Share this post


Link to post
Share on other sites

It has been fixed in ASN...mine is bang on and stable every time.  That's why I suggested if this is a recurring problem with his setup that he create a support ticket at hifisim.  It may have something to do with with how the AS modules are connecting...something may be blocking them.

 

I'll keep monitoring the winds and see if it continues to happen but I'm hoping it was just a random thing. 

Share this post


Link to post
Share on other sites

Hi, 

 

I tried to reproduce this using historical weather around the time you posted the first post, but the winds were not close, so a first suspicion is that you didn't use live weather. Other possible causes:

 

- The winds did actually change from the time you initially obtained the first report. There is an option in ASN (prevent downloads on approach) that will prevent such "surprises".

- Close to KLAS there is at least another  weather station reporting different winds in many cases. If you haven't specified KLAS as your destination (using a flight plan) within ASN, then the final result will depend on both stations.

- The winds may have been variable. While this is included in the metar text, it may not be reported in the atis. ASN does actually take wind variability into account when deciding how to depict winds.

 

It's important to clarify the active date time ASN used when reporting such discrepancies, so that we may have a chance to reproduce the conditions and see what happened. Alternatively, copy paste the metar text from the conditions page. 

Share this post


Link to post
Share on other sites

Yea I did a flight today and the winds were exactly as they should of been so I am guessing I messed something up. Thank you for the detailed and helpful response!! 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this