Corporal thanks for all this inputs.
After all this University Physiscs discussion what really happend was that probably Corporal turned to fast and even on the right speed just didn't give enough time for the vane to adjust to the new situation.
What triggers the stick shacker is the vane out side and they can take a while to adjust if you turn too fast. Like he said it's a Dinosaur after all.
So gotta start the turn slowly and kind of a quick stop between 30 and 45 degrees that should avoid any problems.