Answer I don't know what "axial profile" means, but assume it means an axial flow fan. Stall occurs when the fan can't generate the head needed to keep the flow going. For example, if the downstream duct were partly blocked so flow was restricted. Then the flow around the fan is no longer smooth, but breaks down. The cure is to remove the obstruction or use a fan with wider blades. Stall is a rare phenomenon in properly designed fans.
