ASN and PFPX Winds Aloft

[Budbud 227]

Hi,

 

 

 

In PMDG777 SP1, the ability to re-load the weather into the FMC may become possible. But doing this will do nothing other than alter your flight forecasted weather, not the actual weather encountered. This is not logically realistic.

 

The winds aloft are updated every 6 hours. So when you fly a 12h+ flight, it may be sensible to update the forecast winds aloft to get a better accuracy in the final FOB and ETA if I'm not wrong.

[kterz 49]

A small addition:

 

I don't know how exactly PFPX  works, but in the case of ASN it works in 2 ways:

- Parsing the flight plan as a whole considering things to be static. This is used in the briefing page. I think PFPX works in a similar way, but I may be wrong.

- Being in "live" mode by parsing the remaining of the flight plan, recalculating everything (etas, forecast aloft, taf, metars) with the most current data. This way you can get updated information for the remaining of the flight (e.g. when crossing the atlantic in a transatlantic route). This is used in the "live briefing" (122.05), when hovering the mouse over a waypoint on ASN map and on request by external applications (such as the FMC of the T7). So, this is a good way of getting more current data (than the initially forecasted when on the departure airport).

 

In both cases, for each waypoint, the ETA is calculated recursively and then the the current (or forecast depending on the ETA) weather is calculated. This includes surface conditions (metar or taf) and winds aloft. The winds aloft at the specified ETA (and the cruise speed) are then used as the basis for calculating the next leg time and the ETA of the next way point and this goes on until the fp destination. So, the goal here is to attempt to make things as accurate as possible (with increasing accuracy moving closer to a waypoint/destination). 

 

In the end of course the injected winds/weather will be the current ones (no forecast) assuming ASN works in live weather mode. These may differ from what's predicted, because as Kyle mentioned forecasts are forecasts. In general though, this method has proved to be accurate enough. 

 

I hope I haven't confused you even further

[pcubine 143]

Hi Michael.

 

After changing the speed did you click refresh so that the etas (and the briefing) are recalculated?

 

Yes.

[kterz 49]

Hi Michael,

 

just checked this. You seem to be right and thanks for reporting this. This is not an issue with ASN not using forecast winds though, it's just an issue where changing the speed and clicking refresh does not update the etas as expected. I'll fix this. To force etas recalculation for now follow these steps:

 

- Note down the average winds in briefing page

- Change the speed and click refresh (as you did before).

- Go to the map add a dummy waypoint somewhere, then delete it

- Then go once again to the briefing page and compare the winds to the initial ones.

 

Once again, thanks for bringing this up

[AIR_BUSfahrer 0]

@Kostas: As far as I understood you correctly, ASN is using forecasted wind data within ASN's internal flight planner. This is a very important point for me, as I'm not using this planner. My question is now whether ASN also exports this forecasted data to PFPX, because this is doing my wind and fuel predictions. If I use PFPX' own wind data, I'm having a small slider to change the time for those wind arrows, with ASN data in PFPX this slider is greyed out:

 

PFPX

 

ASN

[kterz 49]

Hi Tim,

 

no ASN does not export forecast winds at the moment. The text file we export has only current aloft layers. This is done this way to keep compatibility with other (older) add ons too. Adding forecast aloft data would make all of them (including PFPX) fail to parse this data. 

 

OTOH, we do export forecast winds at the estimated ETA of a waypoint in the format used by the FMC of airplanes such as the PMDG T7. In this case it's important to set the correct values of cruise speed etc in the flight plan page so that ASN can calculate the ETA/ETE of various way points and then return the matching forecast winds/wx at the given time/place.

[AIR_BUSfahrer 0]

Ok, thank you very much Kostas! That made some points clear to me. :)