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pcubine

Interval for Winds Aloft Update

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I tried this question at ASN/HiFi and struck out. Winds aloft by route waypoints can be requested in the FMC by selecting RTE DATA> on the ACT RTE LEGS and WIND DATA REQUEST> on the next page. After several seconds you are prompted to LOAD and several seconds later EXECUTE. How often are the winds aloft updated so that it makes sense to request the winds? To me it seems about every two hours give or take an hour. If there is definite interval is it tied to UTC time, flight time, or something else?

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If there is definite interval is it tied to UTC time, flight time, or something else?

 

This is a tough question to answer, as we're straddling real versus sim time here. In the real world, we run the model every six hours. From this model, we get 6, 12, and 24 hour forecast periods. If you want the details about it, see here: http://www.flyingactivity.com/mod/fileman/files/FBDoc.PDF

 

As for how often the wind is updated in the sim, it depends on the weather program. My bet is that it updates a lot more frequently than that.

 

As far as a schedule goes, I update the forecast: at the gate, at the top of cruise, on steps, and 100nm prior to T/D (mainly because I'm already in there requesting the DES FORECAST).

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As far as a schedule goes, I update the forecast: at the gate, at the top of cruise, on steps, and 100nm prior to T/D (mainly because I'm already in there requesting the DES FORECAST).

That sounds like a reasonable way to update the winds aloft in the FMC. Quit worrying about what ASN is doing and base it upon significant events during the flight.

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In real world we would try to get a winds update only once (or not at all) because of, as Kyle said, the winds are update only at 00, 06, 12, and 18UTC by the Meteo offices.

 

I thought weather programs like ASN/OPUS got their weather from the same offices so I wonder if those frequent in game weather updates even change anything or you just reload the same winds?

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In real world we would try to get a winds update only once (or not at all) because of, as Kyle said, the winds are update only at 00, 06, 12, and 18UTC by the Meteo offices.

 

I thought weather programs like ASN/OPUS got their weather from the same offices so I wonder if those frequent in game weather updates even change anything or you just reload the same winds?

I am aware of the RW updates every six hours. ASN gets it's information from the same source as the Meteo offices but they do change more frequently than every six hours. How ASN determines what the change is going to be I have no idea.

 

When I originally asked the question on the ASN/HiFI Forum the answer given was by Kostas Terzides their lead programmer was that he didn't know. He came back later after I made the original post here and said he completely misunderstood my question. He said it was updated approximately at one hour intervals.

 

If an update was requested and executed and 45 minutes later another request and update was done its going to load the same winds. Do the update 1:45 after the first and the winds loaded will change but no by much. Several degrees and several knots. Nothing really significant until you consider maybe 30-35 waypoint are involved and then it might change the ETA by 5 minutes. The next update that loads different winds might change the ETA back to the original so it's just a game/playtime.

 

If you don't want to follow Kyle's recommendations, I think the request and execute should be done at 0630, 1230, 1830 and 0030 UTC. This would give ASN the RW forecast plus 30 minutes to digest it.

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The wx engine should update at least hourly to catch METARs and TAFs.... it also just happens to update winds at the same time to keep it simple.  Whether or not there is a wind change in the update depends on time elapsed (upper wind forecasts are 6 hr).  The METARs and TAFs are probably used by the engine to update each station, which is important for the simulation and probably drives such things as clouds, precipitation and storm generation.

 

 

An excellent website for aviation weather designed for pilots is the NWS Aviation Weather site: http://aviationweather.gov/

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The wx engine should update at least hourly to catch METARs and TAFs.... it also just happens to update winds at the same time to keep it simple.  Whether or not there is a wind change in the update depends on time elapsed (upper wind forecasts are 6 hr).  The METARs and TAFs are probably used by the engine to update each station, which is important for the simulation and probably drives such things as clouds, precipitation and storm generation.

 

 

An excellent website for aviation weather designed for pilots is the NWS Aviation Weather site: http://aviationweather.gov/

Yes, absolutely...for Metar and TAF injection into the actual simulation you want regular updates. This after all creates the real world weather we fly in.

OPUS updates this automatically according to the settings....so after XX minutes or XX miles...I am sure ASN does the same.

Shown winds aloft (on the ND) probably change during that update as well as FSX recalculates things....so I bet that even if the same winds aloft file is used by the weather engine, it will still show slightly different winds after the update. Just like that cloud straight ahead is not there anymore due to FSX recalculating things even with the same Metar.

 

But I thought we were talking about the LEGs page wind update into the FMC.

If the winds aloft file used has not changed, then the FMC will be populated with the same winds.

And ETA and fuel at destination, etc, should not change.

There is no recalculation for an FMC wind update with the same winds.....at least not by the FMC and not by the Meteo offices. If ASN or OPUS do change things for a LEGs winds aloft update made every hour then it is doing things a little different. (and I am not saying that bothers me personally).

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I agree Rob, I was getting OT trying to talk to Michael's comments regarding wx engine updates. Seems I totally confused him and didn't add value to the thread.  I'll keep mum, except the winds data in the legs pages only updates when the FMC communications occurs regardless of wx engine updates.

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