As Dozy says, 'AoA indicator' has been done to death (no pun intended) in Tech Log. Yes, a very useful piece of kit. In my (limited) experience in partially jet-borne operations, vital, BUT it does require an understanding of how aeroplanes and wings actually work which so often seems to be missing on PPrune and particularly in the cockpit of 447, and of course, that nightmare !MONEY SPENT! on installation and training.