if you are flying at say FL380 and preparing for descent I usually use the wind speed and direction shown on the nav display as the first forecast but not sure what to put for the other two other than a guesstimate. A couple of questions:-1.How do decide which 3 levels to put in ?2. if you put 'early' levels in say 350/250/200, should you then re-enter 3 more forecasts as you pass the ones you've put in ?3. Knowing how quirky VNAV Path can be, are there ways to fool the FMC by putting specific levels in say TOD/TL/FAF or doesn't it make any difference ?

I have been using (for a TOD of FL380) FL340 FL240 and 12000 for the three forecast levels. Works as well as anything else. The winds that have a magnitude to really make a difference are usually above 12000, so I might use 18000 and the lowest is the winds below that are not significant (<20).I use Active Sky to generate the wind forecasts, as well as the real time weather along my route of flight. This is an add-on that is really worth the minor cost and they provide excellent product support.

Dave,the descent winds are normaly included with the winds page of the flight plan on "real flights". I normally enter the wind from the TOD waypiont ie 380, the the winds normaly provided on the plan are 250 150 and 050. Or in the case of an early descent such as into KEWR winds at intermediate level may be provided eg 12,000cheersJon

I get current winds aloft from my FS FlightKeeper ACARS guage with interfaces with Active Sky. It gives my winds aloft for eache way point and can get updates in flight. Then I just pick a TOD point, a point about in the middle of the planned descent and a point near the bottom of the descent.