Its a little more complicated but essentially that. In SAS mode you can equate it like you, the pilot is the stabilization system. For example in the Jet Ranger, when you hover, you have to fine tune your cyclic and collective to keep the aircraft in a steady hover. This is SAS. Now let's add wind to the simple hover and you start to drift.To stop the drift and get back to your original hover position, you put cyclic into the wind and a little collective to compensate for the loss of lift and pedal since you added collective. This is ATT, or attitude retention. In aircraft with both SAS and ATT, if you only have SAS on and you move the controls, the aircraft will not hold the attitudes you have put the aircraft into. In ATT mode, you press your cyclic and collective trim releases put the helicopter in a nose up with a right bank and let go of the trim sync releases, the ATT mode will take those datums you set and try to hold the aircraft in that attitude (always to limits, and in some aircraft through limits, engine and/or torque). SAS won't do that for you. Now if we go one step forward and add flight director, then it changes those datum values to ones that you set through your cyclic and collective "hats". The ATT will achieve those new datums and the aircraft moves. Hopefully that helps. One could go on with describing the series and parallel actuators and there relationships, auto-trim, etc. but that is for the classroom, n'est pas?
