Right, I mixed that up. With AF447 the initial problem was not the AOA but the very common pitot tube icing, which renders the airspeed indicator useless, thus leading to wrong stall warnings.
Even if the pitot tube is heated (mandatory), very often airframe icing leads to a blocked static port, rendering even more indicators useless.
Even if the pitot tube is heated (mandatory), very often airframe icing leads to a blocked static port, rendering even more indicators useless.
https://en.wikipedia.org/wiki/Pitot-static_system