Deicer zones with shedding-enhanced borders

An ice protection system comprising a first set of contiguous deicing zones;

• wherein:
• each deicing zone comprises an envelope defining an ice-protection area;
• each envelope includes an electrothermal heater layer which converts electric power to heat to deice the corresponding ice-protection area;
• at least two of the envelopes are adjacent and share a common interzone border that extend generally in a direction perpendicular to an airstream direction;
• each of the adjacent envelopes includes an edge region flanking the interzone border;
• and
• the edge regions of the adjacent envelopes are configured to enhance deicing at the interzone border by having nonlinear contours with edge features which project-and-recess in a direction substantially parallel to an airstream direction and to accumulate ice therein.