Sorry for my stupid question!
I've tried to implement NML_Textures to an older X-Plane 10 aircraft. In combination with the original *.obj everything works fine apart from some little areas looking covered by 'ant swarms'. Looking into the *.obj using ac3d I realized that all 'ants'-regions have 1-dimensional texture definitions. I changed the texture coordinates and exported the obj. The saved obj was afterwards edited (copied the working header of the other *.obj).
After this 'procedure' X-Plane no longer loads the NML.png. It seems the BPR algortihm is doing something (thus the ants are there...
)
The 'classic' textures seem to be correct in X-plane 11 but I checked my exported *.obj with modelconverterX and there NO textures are shown.
Any hints?! Many thanks in advance!