Thank you for your answer,
I got most of it, but some stuff is still not making any sense.
- AC is not the same as neutral point for an aircraft? Isn't that the most aft point for the CG with the aircraft NOT beeing unstable? The point where the tailplane arm is to short to create enough pitching motion?
- You say that "the centre of mass of the aircraft must be ahead of the aerodynamic centre." I wish, but even the fwd limit of CG is aft of AC in my book.
- I know that it's possible for the tailplane to create lift in some situations, but in these illustrations it will produce lift even at fwd CG limit. The camber of the tailplane is also positive in these illustrations...