Air leakage restrictor arrangement for an aircraft powerplant

An assembly for an aircraft powerplant, comprising:

• a bladed rotor rotatable about an axis, the bladed rotor including a rotor disk and a plurality of rotor blades, the rotor disk including a web and a rim with a concave disk surface at an inside corner between the web and the rim, the concave disk surface having a disk surface sectional geometry in a reference plane parallel with the axis, and the plurality of rotor blades arranged circumferentially around and projecting radially out from the rim;
• and
• a stationary structure comprising a lip with a convex lip surface, the convex lip surface next to the concave disk surface, and the convex lip surface having a lip surface sectional geometry in the reference plane that matches the disk surface sectional geometry;
• wherein at least a portion of the lip surface sectional geometry is identical to the disk surface sectional geometry in the reference plane in shape and dimension.