When I enter a certain wind direction and strength into the Forecast page of the FMC, you have to enter a altitude too. Does that info only have an effect on that EXACT altitude? Or also above it? Or below it? And how far above and/or below it? And what if the weather hs changed EVERYWHERE, right until the end of the flight...?

It's really info you give to the FMC about the winds. You don't exactly know on wich altitude the wind becomes stronger or not. It's more a tool so the FMC can change things to its calculated path, and also make the ride as economical as possible. If you have a forecast about the winds close to/around aprox. FL100, you can put the info in the FMC so it knows what it can expect around there.Slaap lekker.Cheers,Ian Udinga

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It's quit clear and not at all confusing! :)But I didn't know it was possible to add wind data to a specific waypoint...? I only thought you could read it on the PROG page and add it on the DES FORECAST page... Think i have to read the FMC manual once again... (the first two or three times you read it a lot of things don't get stuck in your head because there is so much new info there, if you know what I mean...)