What type of feature is used to define a new Sketch on a non-planar face?

A Datum Plane is used to define a new Sketch on a non-planar face because it provides a controlled, defined flat surface that can be used for sketching purposes. In CAD systems like NX, a Datum Plane can be created based on three points, two lines, or other geometric entities to ensure that the sketch can be accurately defined in three-dimensional space. This allows the user to create sketches that are necessary for further modeling on surfaces that are not flat, enabling the designer to work with complex geometries effectively.

Using a Datum Plane is essential for maintaining design intent and achieving the desired geometrical constraints, particularly when dealing with surfaces that do not conform to conventional planar layouts. Other options, such as Reference Plane, Sketch Plane, and Construction Line, do not provide the same level of flexibility or control suitable for sketching on non-planar surfaces. Therefore, a Datum Plane is the most appropriate choice for this task.