I'll hazard a guess that an "all-flying" control surface is one in which the entire structure rotates, as is typical of the rudders on an American nuke. "Separate flaps" would refer to things like the stern dive planes on most nukes, where the forward part is fixed, and only the after section moves. This is also seen on the rudders of Akula's and most other Russian nukes. Is this what you're referring to redboat219? Or do you mean the split control surfaces some of the newer boats use, where a small section moves independently for fine trimming?
George "Crazy Ivan" Protchenko
“There are the assassins, the dealers in death; I am the Avenger!”-Nemo
"I'm disinclined to acquiesce to your request; means No!"-Capt.Barbossa