Gas turbine engine airfoil mistuning

A stage for a gas turbine engine comprising:

• a circumferential airfoil array providing a total airfoil count for the stage and that includes first and second sets of airfoils, the airfoil array has first, second, third and fourth arcuate regions, the first and second arcuate regions arranged opposite one another, and the third and fourth arcuate regions arranged opposite one another, the first set of airfoils includes a different vibrational frequency than the second set of airfoils, the first set of airfoils has first primary, first secondary and first tertiary airfoil groups, the second set of airfoils has second primary, second secondary and second tertiary airfoil groups, the first primary airfoil group and second primary airfoil group respectively arranged in the first and second arcuate regions, the first secondary airfoil group and second secondary airfoil group arranged in the third arcuate region, and the first tertiary airfoil group and the second tertiary airfoil group arranged in the fourth arcuate region, the first and second arcuate regions provide greater than 50% of the total airfoil count;
• wherein the first set of airfoils has a different characteristic than the second set of airfoils to provide the different vibrational frequency, the different characteristic is an airfoil spacing;
• wherein the first and second sets of airfoils each have an airfoil spacing based upon a simulated stage airfoil count within +/−10 airfoils of the total airfoil count;
• wherein the first primary group, the first secondary group, the first tertiary airfoil group, the second primary group, the second secondary group and the second tertiary airfoil group each include multiple airfoils;
• and
• wherein the first secondary group, the first tertiary airfoil group, the second secondary group and the second tertiary airfoil group each include the same number of airfoils as one another.