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sagiyanay

DES Forecast - Wind LVL

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Hello guys,

Regarding DES Forecast page,  What is the correct method of  LEVEL / WIND selection?

What 3 levels should i choose to enter winds?

 

Thanks for your advise,

Sagi


Sagi Yanay, VATIL

NGX Driver

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What 3 levels should i choose to enter winds?

I enter the winds for FL300, 18000, and 12000 feet. I use 12000 feet as the lower altitude since I get out of VNAV and go to V/S at around 12000 feet. If I stayed in VNAV until turning to final I would use 6000 feet rather 12000 feet. See page 139 of Tutorial 2.


Michael Cubine
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There is no right or wrong method, it's all up to the individual pilot's technique when it come to the descent forecast page.

 

In the real airplane I usually enter the winds for FL 340, FL300 and FL240 since that's what is provided in our paperwork.  Others use FL340, FL240 and 14000 and just make up the winds for 14000.  Some guys never do anything on the descent forecast page.

 

If you are descending in a headwind you can do nothing with the forecast page and you will be fine.  You may end up having to add a little power to maintain your target speed but you will make all your crossings.  If you are descending in a tailwind I would definitely recommend entering something on the forecast page, if you don't you will find yourself above the path.

 

If in doubt or you don't have accurate wind data always tell the box you have a tailwind.  That will force VNAV to compute the top of descent point farther out and will keep you on the safe side.


Joe Diamond

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There is no right or wrong method, it's all up to the individual pilot's technique when it come to the descent forecast page.

Per this partial quote from FCOMv2 "ISA Deviation and QNH (DEV/QNH)Enter the average ISA deviation for descent in °C (+/–XX°C) or °F (+/–XX°F)", at what altitude do you calculate ISA DEV or do you even mess with? I use deviation based upon the airport I am landing at. Some people use 18000 ft.


Michael Cubine
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Choose levels with the greatest change in wind and/or direction as those will not be in line with the linear assumptions that the FMC otherwise makes.

 

Also, with a strong tailwind, it is often a good idea to make one of the entries just a few thousand feet below the cruise altitude. Otherwise the aircraft could under compensate for the tailwind and the speed starts to climb towards the barbers pole. At least, that is how the real NG can sometimes behave, I've never tested NGX to see if that kind of real world behavior is the same.


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Per this partial quote from FCOMv2 "ISA Deviation and QNH (DEV/QNH)Enter the average ISA deviation for descent in °C (+/–XX°C) or °F (+/–XX°F)", at what altitude do you calculate ISA DEV or do you even mess with? I use deviation based upon the airport I am landing at. Some people use 18000 ft.

 

Our flight plan includes the average temperature deviation, I use that.  Others use the temp at FL180.  Many leave it blank and just put in the QNH setting.


Joe Diamond

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Our flight plan includes the average temperature deviation, I use that.  Others use the temp at FL180.  Many leave it blank and just put in the QNH setting.

 

Thanks for the information.


Michael Cubine
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What 3 levels should i choose to enter winds?

 

Take a look here:


Kyle Rodgers

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