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Wind in A320

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Wind in A320

Old 13th Nov 2009, 21:39
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Wind in A320

somebody told me that unless the wind direction is more than 30 degrees change and or speed is above 10 knots change you don't have to enter it in way points in the MCDU,is that right and what is the reference.because I used to enter all way points.
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Old 13th Nov 2009, 21:52
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The more accurate the data, the more accurate the predictions.

However.

I think a 30 degree change will make a big difference, but only if the wind strength is significant.

Personally I only put the wind in if there is a change of either 10 degrees or 10 kts. This still means that I don't have to put most of the winds in and the forecasts are still very accurate. Also and more importantly I don't have to use my brain that much when I'm in a rush to fill the box up.

FIS.
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Old 13th Nov 2009, 23:34
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Why put in any winds at all

You'll get there when you get there... and you no doubt have a computer generated paper plan anyway, which is the formal (and legal) way of recording/checking FOB etc.. What real benefit is there in keeping the FMGC(s) in exact sync as well?

NoD
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Old 14th Nov 2009, 00:20
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Altitude planning, for one. The flight plan step climb versus the FMGC Optimum step are often hundreds of miles apart. And that's with the winds inserted.

Not inserting the winds is like using cruise control on a hilly road. The poor car is reacting to the small slice of its environment it is aware of, instead of planning for changes.

[Thread Hijack:] Which brings me to another irritation, this constant use of the computerized flight plan as though it were gospel. One pilot will fly fast and hard, then point to the FOB on arrival and declare "I saved XXXX lbs this leg", then the next pilot will fly the cost index, look at the FOB and declare "I saved YYYY lbs this leg." Both think they are heroes. As though bias in the flight planning software, variations in winds aloft, turbulence, direct routing, and ATC constraints don't exist on a leg to leg basis. As though all that matters is the Mach number in the little window. Delusional.

Last edited by Cardinal; 14th Nov 2009 at 00:33.
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Old 14th Nov 2009, 03:51
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to the question.. yes FCOM does say not to alter winds at different waypoints if a difference of less than 30 degrees and 10 kts...(but i also do the 10 degree / 10 kts thing)
the other thing to keep in mind is that the IRS measure actual winds upto 200 nm ahead of the a/c... so really only inserting winds on longer legs makes a difference.
..and the difference it makes is like one other said...accurate predictions and better descent planning, optimum alts....etc
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Old 14th Nov 2009, 07:04
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How can an IRS MEASURE the actual wind 200nm AHEAD of the aircraft??

Do You mean compute a "theoric wind" 200nm ahead according the wind at present position..?
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Old 14th Nov 2009, 10:44
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Greetings,
The IRS (ADIRU) does not measure the wind 200 nm ahead of the aircraft, it is the FMS who is doing the job, by blending the wind entered in the wind page, with the wind sensed by the ADIRU at present position, then the FMS applies a percentage of the resulting blending as per the distance between the present position and the TO waypoint (the active leg) .
For the Pegasus it is 200 nm, for the Thales Smith it 100 nm ( I know, the FCOM says 200 but it wrong)
 
Old 15th Nov 2009, 20:18
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RIRO - Rubbish In Rubbish Out!!

If you put in all the data as per Airbus you will have a wonderful tactical and strategic tool, as the predictions will be accurate to destination and alternate which will enable you to make INFORMED decisions. Flying is about options - so you will be able to test options A to D and more via your FMGS, IF AND ONLY IF ALL THE DATA IS LOADED!!!

Fly safe.
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Old 15th Nov 2009, 21:28
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One relevant, if impertinent, anecdote I can relate ...

Many years ago, at 0-dark-30 on the way over the ditch (pre-FMS days), ATC requested a spot wind.

Now, the three of us, not having made such a calculation for some considerable time all retrieved our various prayer wheels, determined the input data and came up with three quite dissimilar answers.

During a second attempt the answer proved to be just as elusive.

Not being so crass as to nominate my own as being correct, we elected to average the answers, reported L&V to ATC to keep those worthy folk happy .. and still found our way to the destination on schedule ...

Perhaps there is a happy medium with the current fancier kit .. but, at the end of the day, there really isn't any need to measure the sector distance to the nearer millimetre ...
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Old 16th Nov 2009, 01:04
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What difference dos it make????

What difference does it make?

You get there, when you get there...
not before, and not after.

Yogi Berra


(Only joking.....)


Fly safe,

PantLoad
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Old 16th Nov 2009, 04:59
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FCOM 4.04.25 p7 states that the recommended parameters for changing winds in flight at consecutive waypoints are any variation of more than 30kts or 30 degrees.

Change the temperature if it varies by more than 5 degrees celcius.

In other words, all winds should be inserted before take off but only amended in flight if different by the above amounts.

Last edited by flyingins; 21st Nov 2009 at 08:17.
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Old 19th Nov 2009, 13:21
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Greetings
Airbus published the same recommendation for the Long range family, So lets apply it
the flight is 9 heures long, the first hour the wind is 270/30, the second hour till destination 270/5 so 25 kts is less than 30 I should not change the wind
First Hour SAT -55 the second hour till destination -59 so it is less than 5 deg , as per Airbus, I should not change it
25 Kts * 8 hours is 200 mn
4 * 8 hours is 32 mn
Total prediction error at destination is 232 mn is terms of time and fuel
Thank you Airbus
 
Old 19th Nov 2009, 16:55
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kijangnim Greetings
Airbus published the same recommendation for the Long range family, So lets apply it
the flight is 9 heures long, the first hour the wind is 270/30, the second hour till destination 270/5 so 25 kts is less than 30 I should not change the wind
First Hour SAT -55 the second hour till destination -59 so it is less than 5 deg , as per Airbus, I should not change it
25 Kts * 8 hours is 200 mn
4 * 8 hours is 32 mn
Total prediction error at destination is 232 mn is terms of time and fuel
Thank you Airbus

I am going to assume mn is nm, but how do you get 4 degrees temperature change time 8 hours equals 32 miles?
If your not happy with an approximation, and/or it disagrees with your flight plan, you might want to put in more accurate data than that recommended. It will blend with actual wind as the flight progresses.
BD
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Old 19th Nov 2009, 17:23
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Greetings 1 delta ISA is 1 Kts TAS

My comments were about following Airbus recommendation, and I surely know that if you put accurate data then...
 
Old 20th Nov 2009, 02:25
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Sorry,
Thought the recommendation was just that, a recommendation or a starting point to reduce workload for generalizations and not an exclusion to input more satisfactory data. Didn't know about the delta t rule of thumb, thanks.
BD
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Old 20th Nov 2009, 03:03
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Greetings,
The only problem with recommendations is that they often end up in SOPs
 

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