Hi guys,
actually I did not create the tower.
I downloaded the 3D model and the texture files, imported the stuff into AC3D, exported it using the SDK (as assumed by Jet-Pack).
Sounds easy, but in fact it was a lot of fiddling:
Import- and export formates do not match (I played around with sketchup, blender, ac3d),
3d size and orientation has to be redone,
texture positions get lost during different conversions and have to be reset,
texture formats do not fit to the required parameters and have to be reworked,
help required to setup the coordinate parameters (thanks to IPACS),
but finally the result is satisfactory.
I hope to setup a clear way for importing all the 3D models in the internet.
When creating a new 3D model in ac3d, the subsequent steps are identical for the aerofly conversion.