GW3 is not compatible with FSX. Many of it's files, including Afcad2 files and .api macro scenery objects, are not supported. And the setup is not suitable for FSX.
You can visit the GW3 support forums at
The Old Hanger. Most of the newer FS9 vintage scenery add-ons for the era are in the (Gmax) .mdl format supported by FSX. Some members/designers are starting to release their sceneries in FSX as well as FS9 packages.
Dave
PS: If your into vintage, GW3 and the excellent list of FS9 vintage aircraft and scenery, are still good reasons to resurrect your FS9 or even buy it. Current FS9 price on most shelves is now $20 US.
At that time [1909] the chief engineer was almost always the chief test pilot as well. That had the fortunate result of eliminating poor engineering early in aviation.