Cmc vane with detuned platform

A method comprising:

• for a design geometry of a ceramic matrix composite (CMC) vane arc segment that has a platform and an airfoil section that extends off of the platform, wherein the platform defines an axially trailing face, an axially leading face that is circumferentially offset from the axially trailing face, and first and second circumferential faces that extend from the axially trailing face to the axially leading face, determining a modal excitation response of the platform under cruise conditions;
• and
• if the modal excitation response is greater than a target modal excitation response, adjusting the design geometry of the platform to be detuned with respect to a natural frequency of the platform differing by a predetermined margin from an external engine operation excitation frequency of turbine blades that rotate past the CMC vane arc segment by reducing an overhang distance of the platform to produce a detuned platform in which the modal excitation response at the cruise condition is equal to or lower than the target modal excitation response.