ATPL theory questions

[Skymaster15L]

Va and Vno-when to use each

Happy New Year to Everyone.

Have been studying the limitations chapter in POF and in particular, the V-n diagram that deals with the load factor limits of the flight envelope, and the various important speeds that you find on that envelope.

Comparing the definitions of both Design maneuvering speed (Va) and Max Structural cruising speed (Vno), I am a bit confused. I would like to know what exactly is Vno useful for? I understand it is the limit above which flight should be attempted in smooth air only (no turbulence?) and then only with caution. Why is it then that everywhere else I read, it says that when encountering turbulence you should slow down below maneuvering speed, in addition to when you are engaging in maneuvers, etc.

I am aware that the definition of Va is often a varied one and commonly misunderstood by many pilots, usually along the lines that you think you are guaranteed in throwing unlimited abuse at an airplane thru abrupt control deflections, etc without having it fail as long as you are below Va, so I am not inviting to dissect this subject unless necessary in answering this post.

So based on the definitions from aviation textbooks of what each speed is, I'd simply like to know which one should be used for what then and why? I too would think Va is the more important one, since it deals with protecting the airframes structural integrity, but then I also been in many an airliner that when it has experienced turbulence, I've never perceived it to slow down a substantial amount as if it was aiming for a speed below Va. So then, in which circumstances does Vno has a practical application?

Thanks