What is the correct procedure? I can't find any good info in the manuals. (i'm sure it's there but it's such a pain to search through them)

For which altitudes should you enter winds? For how many altitudes? Is there a rule of thumb? Do you have to change the values if the forecast changes a bit?

The manuals give good info on how the system works, but not how to use in an operational sense, so don't feel bad.

 

The idea is to get forecasts at a good spread of levels that you might encounter en route to allow the FMC to calculate a recommended level. Note that this may differ from the optimum level.

 

How you accomplish this is largely dependent on what if any flight planning tools you have. PFPX for example will allow you to export winds at multiple levels directly to the PMDG 777.

 

Once you've got the winds into the FMC during preflight you wouldn't change them en route.

The manuals give good info on how the system works, but not how to use in an operational sense, so don't feel bad.

 

The idea is to get forecasts at a good spread of levels that you might encounter en route to allow the FMC to calculate a recommended level. Note that this may differ from the optimum level.

 

How you accomplish this is largely dependent on what if any flight planning tools you have. PFPX for example will allow you to export winds at multiple levels directly to the PMDG 777.

 

Once you've got the winds into the FMC during preflight you wouldn't change them en route.

Actually I was referring to the winds you have to enter in the FORECAST page. For enroute winds I just use the import function but you can-t do that for the FORECAST page and I'm not sure for which altitudes etc.

 

Verzonden vanaf mijn GT-I9300 met behulp van Tapatalk

 

 

Oh right. Well I think most of what I said still holds true, you want a good spread of winds on different levels.

 

In the real thing you might well download updated winds via ACARS on enroute.

 

 

Actually I was referring to the winds you have to enter in the FORECAST page

 

I feel like I've answered this question before...

 

Ah! Yep!

 

(This was written for the NGX, but the same theory applies)

Looks like I need to do a tutorial on this as this is the second question I've seen on it today.  The rule of thumb is that you want to choose the altitudes with the most amount of variation.  As an example (using wind right now over ROA):

 

FT  3000    6000    9000   12000   18000   24000  30000  34000  39000

 

ROA 2911 3214+16 3116+11 3112+05 2615-08 2917-18 340933 361644 350756

 

Say we're going to descend from FL350 over ROA.  Anything under FL350 is potentially useful for me, though 3000 and 6000 probably aren't, because most TRACONs pull you off of your VNAV path and assign you altitudes on their own instead.  So, we're left with this:

 

FT 9000   12000   18000   24000  30000  34000

 

ROA 3116+11 3112+05 2615-08 2917-18 340933 361644

 

As you can see, it's pretty linear, with not too much out of order.  There's a reasonably-sized jump between FL180 and 12000 in direction (about 50 degrees).  That's worth noting.  The FL340 speed is likely so close to our current altitude that it doesn't do us much good.  From there, I'm mainly concerned about the 50 degree jump (FL300-FL240), the 30 degree jump (FL240-FL180), and the next 50 degree jump in the wind (FL180-12000).  Since our current situation is probably Those altitudes are FL300, FL240, FL180 and 12000, so I'd use those.

 

Always look for jumps:

Big changes in direction

Big changes in velocity (in this case, there are some changes, but none too crazy)

 

As far as only entering them for the IDLE part of the descent is a good one.  It would certainly help to have more of the information in that part of the descent, but it isn't wholly worthless to add wind entries below that.

 

 

ROA 2911 3214+16 3116+11 3112+05 2615-08 2917-18 340933 361644 350756

Excuse my stupidity, but I'm not sure how to read these numbers. If I look at the end of the numbers, I see 350756 for example, which - I assume - should be read like 350 degrees / 75 KTS, but what number is the 6 for? TAT?

And then in the beginning it says numbers like 2911 or 3214+16, which is all confusing me. 291 degrees / 1 KTS and 321 degrees / 4 KTS with TAT of +16? 

Again, excuse my stupidity. 

Im interested in this too. Looking forward to read the replies.

Again, excuse my stupidity. 

 

Not stupid...just don't have a degree in trying to figure out outdated data formats from the dark ages of trying to make data easily available via teletype and 56k connections...

 

Here's the official FYI/Help form the Aviation Weather Center:

 

FT 3000 6000 9000 12000 18000 24000 30000 34000 39000

 

FT indicates the forecast location, the numbers indicate the forecast levels. 

 

MKC 2426 2726-09 2826-14 2930-21 2744-32 2751-41 275550 276050 276547

 

This example shows data for MKC (Kansas City, MO). The 3,000 foot wind is forecast to be 240 degrees at 26 knots. The 6,000 foot wind is forecast to be 270 degrees at 26 knots and the air temperature is forecast to be -9 degrees Celsius. The 30,000 foot wind is forecast to be 270 degrees at 55 knots with the air temperature forecast to be -50 degrees Celsius. 

 

Wind direction is coded as a number between 51 and 86 (vice 01 to 36) when the wind speed is 100 knots or greater. To derive the actual wind direction, subtract 50 from the first pair of numbers. To derive wind speed, add 100 to the second pair of numbers. For example, a forecast at 39,000 feet of "731960" shows a wind direction from 230 degrees (73-50=23) with a wind speed of 119 knots (100+19=119). Above 24,000 feet the temperature is assumed to be negative, therefore the third pair of numbers indicate a temperature of minus 60 degrees Celsius. 

 

If the wind speed is forecast to be 200 knots or greater, the wind group is coded as 199 knots. For example, "7799" is decoded as 270 degrees at 199 knots or greater.

Wind direction is coded to the nearest 10 degrees. When the forecast speed is less than 5 knots, the coded group is "9900" and read, "LIGHT AND VARIABLE."

 

-----------

 

Also, no temperatures are forecast for the 3,000 foot level or for any level within 2,500 feet of station elevation. Temperature is in whole degrees Celsius and assumed to be negative above 24,000 feet. 

 

 

 

 

 

 

Looking forward to read the replies.

 

See post #5