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How to effectively use des forecast

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What sort of intervals should you use when inputing wind speeds into the descent forecast? i often use 5000ft, but i never know if that is correctcheers


Alaister Kay

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I have no clue, but I would think seperating between altitudes is important.For example, if I'm only at FL240, I'd start with 18,000 as my first altitude, then 10,000, then something inbetween 10,000 and the landing altitude.If I'm as high as FL340, I'd maybe go 20,000 ---> 10,000 ---> then something inbetween 10,000 and my landing altitude.


- Chris Jefferies

 

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Guest ZOTAN

Sorry, I accidentaly double posted...How do you delete?Thanks,Matt

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Guest ZOTAN

How do you find out the speed and direction of the wind?Matt

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You only double posted because you asked how to delete a double post in the first place. A little Ctach 22 there :) just kidding.Finding out how your winds are gonna look like is fairly easy. You could use ActiveSky which is an add-on for FS9 that takes control of the weather engine and manages weather much better than the built-in thing (but you'd have to pay a reasonable amount for it); or you could do it like real world pilots do - going to a web source that has Wind charts. One such example, and which is very accurate, is: http://adds.aviationweather.gov/winds/All you have to do is look up the charts for the time you'll be flying Zulu and the Flight levels you're interested in. But these charts only cover North America. If you are an internaitonal airman, you can access http://www.noaa.gov/aviation.html and click International Flight Folder and then select the charts from the world area where you'll be flying in the same fashion as described above. These wind charts are published twice daily, @ 0000Z and 1200Z and they are valid for 06/12/18/24/30/36 hours counting form the time they are made (either 0000Z or 1200Z). They are very simple to read. the number indicates the NEGATIVE temperature in degrees celsius (meaning they will only mean a positive temperature if marked by a positive sign). The wire indicates wind direction and the barbs or flags indicate the wind speed. Flags mean 50kt, log barbs 10kt and short ones 5kt. The flags and barbs are placed on the upwind end of the wire. so a horizontal wire with 2 flags and one short barb positioned on it's left extremity means winds from 270 degrees at 105kt. Hope it helps.Regards, Victor http://www.precisionmanuals.com/images/forum/800driver.jpg


Cheers,
Victor M. Lima
 

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If datas are available I personally prefer to enter winds along the descend path at FL290, FL210 and FL130 to get the FMC to calculate the correct TOD point. If not entered properly according to current winds conditions, VNAV may be rather useless. There are others but this is one very common reason for getting the des path unavailable message and a VNAV disconnect.

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Guest Zapper

Hi All,IRL the DES Winds are indicated on the flight plan from Ops and you will enter these into the DES Forecast page at any time prior to ToD. For us they are FL 290, FL210 and FL130. We all do it in the before flight set up unless you are in a real hurry to meet a slot time or the coffee is going cold or some other diabolical problem :DThe whole purpose of the DES Forecast page is to refine your VNAV ToD point to provide the optimum Idle Thrust glide path to the runway of intended landing, taking into account any madatory heights/speeds you may be required to meet.The QNH only needs to be enetered if it is above 1013 as any QNH above that reference value would cause you to be high on approach if not allowed for. Temp is same.. they both affect what is called 'Density Altitude'The ANTI-ICE ON/OFF area is a guess as to where you reckon you will use it on DES as when EAI is 'ON' it increases the N1 a bit to ensure adequate bleed air supply which means higher than IDLE THRUST and so will put you a little high on profile if you had only calculated for an IDLE THRUST glide descent.This all make sense? ;DRgds,

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Guest aarskringspier

I was right there with you up to "The coffee getting cold....."

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Thanks for the info, makes perfect sense to me :-) Just need to fill in the fields earlier :-)


Alaister Kay

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