backface culling problem on a mesh

Hi guys,
I’m pretty a noob with blender but I’m trying to make a game with BGE. Now I’ve a problem with a mesh, when I render with the “normal” blender render it’s fine but when I try to render with BGE some part of the mesh is invisible and I think (am I right?!) the problem is the backface culling. I tryed to usi a solidify modifier but it didn’t work… Any suggest?

blend file:

Thanks

You need to recalculate outside normal in blender.

I’ve already tried to recalculate outside normal but it didn’t work.

I tried but it didn’t worked.

I tried but it didn’t worked.

I tried but it didn’t work.