A320 Fmgs Wind Data

[HOTROD_0414]

Greeting guys, tried my best to look in FCOM 4 for this, but still couldn't figure it out.

During cruise, what is the significance of entering CRZ WINDS? Are these winds used by FMGS by any way for predictions? My understanding (may be wrong) is FMGS measures ACTUAL winds upto 200 n.m. ahead of a/c for prdictions. (FCOM 4.04.25)
Really appreciate any kind of help on this topic

[wanabe2010]

4 fuel calculation.

[kijangnim]

Greetings,
WInds along with temperature and tropopause height are used for PREDICTIONS, in which fuel is included, and to compute the optimum FL.

[PappyJ]

During cruise, what is the significance of entering CRZ WINDS? Are these winds used by FMGS by any way for predictions? My understanding (may be wrong) is FMGS measures ACTUAL winds upto 200 n.m. ahead of a/c for prdictions.

Your understanding is correct. It does use the actual winds for "Updated" predictions 200 miles ahead of the current position. It then uses the "Entered" winds for those predictions beyond 200 miles.

WInds along with temperature and tropopause height are used for PREDICTIONS, in which fuel is included, and to compute the optimum FL

Also correct.

Cheers

[kijangnim]

Greetings
200 nm is correct for the Pegasus, for thales it is 100 nm

[kijangnim]

Greetings,

1.3.2.2.1 Wind modeling
The Wind modeling follows the flight in its logical order, departure,
climb, cruise, descent, and destination.
Because of similarities, we can pair
Departure and Destination
Climb and Descent
1.3.2.2.1.1 Departure and Destination winds:
These winds refers to wind below from 400 ft AGL to 0 (GRND)
1.3.2.2.1.2 Climb and Descent Winds:
Climb and Descent Winds can be defined for 5 altitudes.
Each altitude and its associated wind magnitude and true
direction, is either defined by the pilot or up linked if AOC
function is available.
Furthermore, during Descent, the FM will record the wind at the
Cruise FL, then at FL, 250,150,050, and store these recorded
winds in the History wind page.
Considering that while in transit the turn around time is less that
it takes to the wind to change, the crew can select the history
wind values, and use them as data for the next climb.
1.3.2.2.2 Wind interpolation:
1.3.2.2.2.1 During climb:
If the predicted altitude at a waypoint is above the Highest
entered wind altitude, then the predicted wind at this
waypoint is equal to the Highest entered wind magnitude and
true direction.
If the predicted altitude at a waypoint is between 2 entered
winds altitudes, then the predicted wind at this waypoint is
equal to the linear interpolation between the 2 entered wind
magnitude and true direction.
If the predicted altitude at a waypoint is below the lowest
entered wind altitude, then the predicted wind at this
waypoint is equal to the linear interpolation between the
lowest entered wind magnitude and true direction, and
000/00kt or the GRND data if available.
1.3.2.2.2.2 During Descent:
If the predicted altitude at a waypoint is above the highest
entered wind altitude, then the predicted wind at this
waypoint is equal to the linear interpolation between the last
predicted cruise wind and the highest entered wind
magnitude and true direction.
If the predicted altitude at a waypoint is between 2 entered
winds altitudes, then the predicted wind at this waypoint is
equal to the linear interpolation between the 2 entered wind
magnitude and true direction.
If the predicted altitude at a waypoint is below the lowest
entered wind altitude, then the predicted wind at this
waypoint is equal to the linear interpolation between the
lowest entered wind magnitude and true direction, and
000/00kt or the GRND data if available.
1.3.2.2.3 Wind blending during climb and descent:
During Climb, The FM will blend the actual measured wind with the

predicted wind 2000 feet above the a/c altitude until the

T/C is reached.

During descent , The FM will blend the actual measured wind with the
predicted wind 2000 feet below the a/c altitude, from the
T/D until 400ft AGL.
1.3.2.2.4 Cruise Wind:
Forecast wind is determined at each waypoint and pseudo waypoint along the
F-PLN in the following way :
Cruise wind input data is propagated on the CCRZFFPLNwaypoints until another cruise wind input data is found and so on up to the last CRZ waypoint.
T/C forecast wind (or A/C actual wind) is propagated up to the first cruise wind input data before entering to CRZ phase.
After CRZ phase is entered, A/C actual wind is propagated upto the first cruise wind input data.
1.3.2.2.4.1 Wind ENTERED n cruise waypoints
The FM bBlends wind linearly from actual measured wind at PPOS to ENTERED wind on the upcoming (next) waypoint in cruise when within 100NM: at 90nm uses 90% ENTERED wind and 10% actual emeasured wind, at 80NM, 80% ENTERED wind and 20% actual measured wind, at 100 NM the FMS uses 100% of ENTERED wind

To compute the predictions, the FM then interpolates between act wind and BlendedEEENTERED wind linearly same scheme within 100nm

PLEASE COPY PASTE BECAUSE THEY WONT BE ANOTHER EDITION, AND THIS IS VALID FOR THE LONG RANGE FAMILY ie A340 A330

[PappyJ]

THIS IS VALID FOR THE LONG RANGE FAMILY ie A340 A330

and me thinks that post was .....

A320 Fmgs Wind Data

I recall that there are differences, albeit subtle.

[kijangnim]

PapyJ do you think that I cannot read titles?
Since you are on A330......you might use it or do you consider that since it is published for A320 subject you are not going to use it

[PappyJ]

You must be French!

[kijangnim]

Wrong again

[HOTROD_0414]

Thanks guys for your inputs. By any chance entering CRZ WINDS (that are shown on ND) FMGS calculates predictions till TOD and after that descend winds take over?
I tried it recently entering 100kt headwind and saw the arrival time at destination and then put in 100kt tailwinds and saw the arrival time. There was almost a diff of 10-12 min. I would assume winds entered would be used by FMGS till TOD and not just after 200 n.m.

As per my company SSOP's "Either put winds for every cruise way point or just enter trip winds, if short on time "

[I-2021]

Hi HOTROD,

What I do on short trips is either using the average wind component on Thales 2 equipped airplanes (INIT B page) or for Honeywell systems I insert a couple of CLB winds, some CRZ winds and also a couple of DES winds. That gives me predictions close to about a hundred kg which is ok.

Bye

[pineteam]

Hello guys,

I tried like crazy to find in the FCOM where it says that the FMGS measures actual winds up to 200 Nm (Pegasus) and 100 Nm (Thales) ahead of the aircraft for predictions but I can't find it anywhere.

The only thing I found is : " The system calculates and displays predictions for all the waypoints.
It uses current wind to compute preditctions for the To waypoint, and uses predicted winds for computing all others"

Source: FCOM- Aircraft systems- Auto Flight- Flight management- Control and indicators- MCDU- Page description.

Bonus question: Do you know why sometimes the TOC prediction displayed on the ND is so inaccurate? Sometimes by like 30/40 nm even in the newer aircrafts..

Thank you for your help.

[Tiennetti]

DSC 22_20-30-20-25: Wind, Temperature, QNH

As far as i understand from the FCOM, there is no "blending" of the winds on A320?

[safelife]

[pineteam]

Hello Safelife,

Thank you for your input but where can I find this information? Cause it's not in the latest A 320 FCOM.

and what kijangnim posted is very interesting but applicable to the A 330/340; Not sure if it's the same for A 320? And I believe it's for the the Pegasus FMGC not the Thales?

Tiennetti, I have read that also in the FCOM but I believe this can't be possible since sometimes we get some "direct to" up to a waypoint more than 400 nm and the wind is completely different so this would probably give really inaccurate predictions.

I also checked on the "Thales FM Piloyt Guide" and nothing in details about it..

Does anyone knows how it really works the wind predictions on Thales and Pegasus and where can i find the information? And what if we have a "direct to" and we don't put the abeam waypoints? Is the system ignoring the wind we had inserted at those waypoints?


Thank you again.

[Natstrackalpha]

Pilot entered Winds at different levels

I thought the FMGS could calculate the real wind during flight and that putting the winds in, either manually or uplinked, would just save the FMC from doing loads of calculations in order to arrive at correct predictions like EET, ETA, optimum FL, FOB and all stuff of a predictive nature. If it (the FMGC) is not over busy doing one thing it might be better disposed to take on more work.
So in all, by entering in all the winds you will get greater accuracy from an already accurate system and it is less hassle for the computer, the FMGS one. I think it runs on your entered values and then it is not far from calculating the ambient (real) wind(s) therefore less work to arrive at more accurate predictions, dont forget the GPS, Radio aids and IRS/INS are helping along too.

[vilas]

Pineteam
According to AB presentation of 2009 How to optimise FMS predictions, the FMS creates two wind models a forecast model based on pilot entries of wind and temp and predicted model based on adjustment of forecast model using current data. From PPOS there is a blending zone till a beyond a few way points. There is a difference in A320 and A330 models. In 320 forecast is beyond first way point in 330 it is till first WPT. There are more differences in climb cruise and descent. The impact on A320 OPT alt can vary upto 2000ft for 5 degree of dela ISA or 30kt delta wind. On A330 it is 1000th for 5 degree variation and 2000ft for 30kts variations