While in flight, information about wind strength and vectors is shown to us by the FMC. Therefore, if it already has this information, why should it be necessary to program wind/vectors when the FMC is aware of it on an ongoing basis? Surely it uses the information it already has to plot it's optimum heading?Cliff Harris

Cliff,The aircraft can tell the wind at its current position, it cannot predict the winds forward of its position, or at different altitudes. You have to tell it what to expect from the wind charts.

While in flight, information about wind strength and vectors is shown to us by the FMC. Therefore, if it already has this information, why should it be necessary to program wind/vectors when the FMC is aware of it on an ongoing basis? Surely it uses the information it already has to plot it's optimum heading?Cliff Harris

The FMC cannot see into the future, the purpose of entering the winds is to allow the FMC to make accurate predictions for fuel consumption.

Surely it uses the information it already has to plot it's optimum heading?

The FMS is not plotting a heading, it is providing a course to the autopilot/flight director system whose job it is to maintain the course.

The FMC cannot see into the future, the purpose of entering the winds is to allow the FMC to make accurate predictions for fuel consumption.

Got it.Now I understand. ThanksCliff

The FMC cannot see into the future, the purpose of entering the winds is to allow the FMC to make accurate predictions for fuel consumption.

Rob how do YOU enter the winds and vectors into your FMC? The reason I ask is because I've discovered that "Active Sky" doesn't input Flight Plans with file endings of .rte.but needs plans produced by Flight Simulator. I use "VRoute" for my Plans and they export in .rte format suitable for "The Queen".I'm therefore trying to learn if there's a way around this problem.Cliff

The reason I ask is because I've discovered that "Active Sky" doesn't input Flight Plans with file endings of .rte.but needs plans produced by Flight Simulator. I use "VRoute" for my Plans and they export in .rte format suitable for "The Queen".I'm therefore trying to learn if there's a way around this problem.

Simply export twice from vRoute. Use the "Flight Simulator 2004" option, Active Sky can read that.

Anyway how can we input Wind predictions into the FMC?

Simply export twice from vRoute. Use the "Flight Simulator 2004" option, Active Sky can read that.

I've just tried that Tom but no luck.After following your suggestion I was left with two flight plans from KSFO to KLAX in the PMDG folder. One being the original .rte Plan and the other the new PLN Plan.I launched FSX and programmed the FMC with the Company Route of KFSOKLAX. It was accepted and further programming went without a hitch.But here's the rub. When hitting the VNAV button and moving to page 3, then pressing "Forecast" on line 6R, yielded the page still unpopulated with winds/vectors.Have I gone wromg somewhere?Cliff

Simply export twice from vRoute. Use the "Flight Simulator 2004" option, Active Sky can read that.

I did as you suggested Tom. That gave me two KSFOKLAX Plans: one being rte and the other being PLN.After launching FSX I programmed the FMC with KSFOKLAX with no problem.I then launched Active Sky and printed out the winds and vectors as follows:PORTE 18 knts, 246 degreesAVE 31 knts, 214 degreesSADDE 43 knts, 224 degreesI hit VNAV and moved to page 3. Then hit "Forecasts" at line 6/RAs the resulting page was unpopulated I entered PORTE into the scratch pad hoping to enter the information manually.However my entry was not accepted as shown in my attachment.Have I gone wrong somewhere?Cliff

You still have to enter the winds in to the FMS, you've provided the wx program a flightplan on which it bases the forecast but the forecast doesn't automatically get into the aircraft systems.On the DES Forecast page, you enter altitude/dir/speed. For the SADDE arrival you might use forecasts in the 30's 20,s then one at 10000 but it is interested in alitudes not fixes or locations.

You still have to enter the winds in to the FMS, you've provided the wx program a flightplan on which it bases the forecast but the forecast doesn't automatically get into the aircraft systems.On the DES Forecast page, you enter altitude/dir/speed. For the SADDE arrival you might use forecasts in the 30's 20,s then one at 10000 but it is interested in alitudes not fixes or locations.

Oaky doaky...............it's making sense now.My thanks to all of you.Cliff

Yeah it's really important to realize that the winds are something that applies to VNAV path calculation and fuel prediction, not to the lateral flight path. The FMC plots the same LNAV track over the ground regardless of what the winds are, the plane will just be at a different crab angle depending on the wind so that the ground track remains the same. (unless it's a "keep heading" or VECTORS pseudo waypoint leg)Try doing a VNAV descent sometime with a strong headwind or tailwind present, but without wind prediction entered into the FMC. What you'll notice is that you're constantly high or low on your vertical path if the predictions aren't entered. You're also going to end up with too less or more fuel than what the PROG page is telling you when you land too if the change in ground speed (and thus flight time) due to wind isn't taken into account.

On a real world flight recently I`d entered all the en route winds into the FMC but hadn`t put the descent forecast winds into the machines VNAV descent page. I remembered I hadn`t done it but I thought I would leave them out as I didn`t think it would make much difference and the aircraft would just use its current sensed wind to work out a top of descent point.I was wrong, the VNAV path was all over the place and almost unusable, I ended up using FLCH for a large part of the descent. Lesson learned there.CheersJon Bunting