its roughly 18 years ago that I flew a Cheyenne II, but the SAS is - the TO said - a "stability augmentation system", basically it varies the force you need to exert to bring the nose up. The II (which really was the first Cheyenne to be build) had provisions for an eight seat in the baggage compartment which brought the CoG back considerably. And it has roughly twice the power of its origin, the Navajo. It also has a power limitation when approaching a stall, otherwise sheŽll depart controlled flight. The AoA vane drives an AoA meter and a device that requires more force to keep the nose up the slower you get.
Hope my memory isnt as bad on this one as it is on finding my keys...