Mix flour, sugar and salt in processor. Add butter and shortening. Using on/off turns, process until mixture resembles coarse meal.
Drizzle 3 tablespoons ice water over mixture. Process just until moist clumps form, adding more ice water by teaspoonfuls if dough is dry.
Gather dough into ball; flatten into disk. Wrap in plastic; chill until dough is firm enough to roll out, about 30 minutes.
Roll out dough on lightly floured work surface to 12-inch round. Transfer dough to 9-inch-diameter glass pie dish. Fold overhang under. Crimp edges decoratively.
(Can be prepared 2 days ahead. Cover and refrigerate.)
You can use a pastry blender if you don't have a food processor, it will just take more time. Use the pastry blender to work the butter and shortening into the flour until it reaches that cornmeal consistency.