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radeon29

variable wind, tropo and ground temperature on MCDU

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I have a few questions on the MCDU, if anyone can answer my questions it will be useful:)

1)Where to get this value is the tground temperature for take off( GND TEMP)? Or is it not implemented, does not affect anything?

2)Where to get this value is the tropo( tropopause)?

3)How to enter the wind value correctly, if it is variable?

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Hello radeon29,

Sorry for the late answer.

1) Ground temperature for takeoff can be found from the METAR and is the actual outside temperature on ground level.
2) I think some flight briefing softwares like PFPX or Simbrief might give you this value. If not directly at least on the Significant weather chart or Vertical Profile chart where you can estimate this value.
3) To enter the wind data correctly I use Active Sky's Flight Plan feature. If you load a flightplan there and then go to the Airbus MCDU INIT A page and go to Wind page and request wind and update it.

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On 7/31/2019 at 2:49 PM, Secondator said:

1) Ground temperature for takeoff can be found from the METAR and is the actual outside temperature on ground level.

yes, I found this, real pilots just use the outside temperature

 

On 7/31/2019 at 2:49 PM, Secondator said:

2) I think some flight briefing softwares like PFPX or Simbrief

I have a PFPX but I can’t find this information, maybe you have a manual or screenshot?

 

On 7/31/2019 at 2:49 PM, Secondator said:

. If you load a flightplan there and then go to the Airbus MCDU INIT A page and go to Wind page and request wind and update it.

yes, I use this function but that’s not what I asked.

I meant how to enter the wind for the APP phase (there we enter the value only by hands) if it is variable, it is probably best to leave this item empty?

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Hi Radeon29,

 

5 minutes ago, radeon29 said:

I have a PFPX but I can’t find this information, maybe you have a manual or screenshot?


Seems like PFPX doesn't actually support Tropopause at this time. So my memory did not serve me well there. On Simbrief flight plans it can be found on the Navlog under TRP section. For a single value T/C Tropopause can be used.

 

6 minutes ago, radeon29 said:

I meant how to enter the wind for the APP phase (there we enter the value only by hands) if it is variable, it is probably best to leave this item empty?


I am not sure if there are different SOPs on this but I think one common way is to enter just 000 since the wind direction is unknown. For example if METAR reports VRB05KT, I would enter 000/5 on the MCDU approach winds. If the wind direction is varying between two values (reported on METAR like 27010KT 200V350) I enter only the base wind value.
 

 

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12 hours ago, Secondator said:

VRB05KT, я бы ввел 000/5

 

12 hours ago, Secondator said:

METAR like 27010KT 200V350

maybe in this case it’s better not to enter anything at all? but just click clear(leave the field blank),because 000 it will be calm and this is wrong...

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If you enter wind 000/5 into the FMGS, this means that the FMGS thinks you have 5 knot wind coming from the North, not calm wind (000/0).  Since wind is variable the direction doesn't really matter. I have just seen that it's common to just end North as the direction so that's what I have been doing. I am not sure but some airlines could also enter the wind as full headwind for the runway for maximum vapp buffer, so as I said there could be many different SOPs

If the wind is reported 27010KT 200V350, I would enter 270/10 into the FMGS as 270 is the base direction.

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7 minutes ago, Secondator said:

If you enter wind 000/5 into the FMGS, this means that the FMGS thinks you have 5 knot wind coming from the North

so if it is variable we don’t know exactly  from the north or from the south)))

and if the direction is 200V270? what to enter correctly?

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That is correct. Since the wind is variable it can be from any direction but the direction cannot be determined (there are several rules into wind reporting on ICAO documentation but I will not go there now). Therefore the direction doesn't really matter as it's constantly changing.  North is just an easy direction to put in there in such situations.

Wind direction can never be reported variable between two values without a base wind being reported. If the wind direction is between 200 and 270, then the METAR would read something like 24010KT 200V270. So in such situations there is always some base wind direction reported.

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2 minutes ago, Secondator said:

 (there are several rules into wind reporting on ICAO documentationbut I will not go there now). Therefore the direction doesn't really matter as it's constantly changing.  North is just an easy direction to put in there in such situations.

 

2 minutes ago, Secondator said:

something like 24010KT 200V270. So in such situations there is always some base wind direction reported.

Now understood, thanks!

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As for the performance prediction you would just take a variable wind as a direct tailwind, for the FMC, as long as it is less than 5kt you can simply leave the field blank.

You might want to update it if the tower gives you a steady wind when calling, if it's still variable at that point you can simply keep it empty.

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On 8/2/2019 at 11:23 PM, Secondator said:

On Simbrief flight plans it can be found on the Navlog under TRP section. For a single value T/C Tropopause can be used.

can anyone take a screenshot of where it is?

maybe it can be seen in the weather engine ActiveSky?

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8 hours ago, radeon29 said:

can anyone take a screenshot of where it is?

maybe it can be seen in the weather engine ActiveSky?

 

Are you asking about the winds at cruise?  If so, yes, ActiveSky is a terrific source for this and the one I use.  Simply load the flight plan into ActiveSky and then select the briefing tab and you'll find the average winds for your flight plan at the very top along with something very important, the average temp and Temp at Top of Climb (TOC) which you might usually enter into INIT A page.

 

 

Screenshot - 2_29_2020 , 10_01_23 AM.png

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And for the Tropopause value from Simbrief flight plan I have highlighted here in yellow all the values in the default Simbrief OFP format. I have also highlighted with my mouse the TOC values, where I take the Tropopause value (55300 feet in this case) into the MCDU.

image.png
 

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41 minutes ago, Secondator said:

And for the Tropopause value from Simbrief flight plan I have highlighted here in yellow all the values in the default Simbrief OFP format. I have also highlighted with my mouse the TOC values, where I take the Tropopause value (55300 feet in this case) into the MCDU.

image.png
 


 

 

Take a look at the latitudes compared to the tropo... really explains how the tropo works / is shaped!

 

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Good info!

 

Dont forget to, as flight progress, change the tropopause on INIT A if it changes significantly because eventually it may change your OPT FL.

 

About the winds for appr, in case of variable, one of the techniques is to insert that value as tailwind. this is to prevent the worse case scenario as this data may also be used by RAAS if equipped. Tailwind is also used for landing performance assessment in those cases.

 

Remember that to accomplish the "safety first" target, being conservative is key.

 

Safe flights!

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13 hours ago, DaveCT2003 said:

Are you asking about the winds at cruise?

I mean a little different, namely what Secondator is talking about, is there a similar function in ActiveSky?

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6 hours ago, radeon29 said:

I mean a little different, namely what Secondator is talking about, is there a similar function in ActiveSky?

 

No, ActiveSky does not map the Tropopause.  However it is important to remember that for aviation, the Tropopause model is almost always a model rather than a measurement.  This was true for the Concorde and 99.9% of very high altitude military aircraft (at least when I was flying).  For our purposes, and I believe what Derek at Simbrief uses, is the average model based upon Latitude (see  my post above), especially because mapping the actual Tropopause is far, far more complicated and requires a very specific effort, and as I mentioned it is (or was) rarely used in aviation.  I'm sure TGoncalves  is more current and can tell us if things have changed.

 

 

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