Mistuned rotor for gas turbine engine

A fan for a gas turbine engine, the fan comprising blades circumferentially distributed around a hub, the blades having airfoils with a span defined between a root and tip of the airfoils, the airfoils having a chord defined between a leading edge and trailing edge of the airfoils, the airfoils having a thickness defined between a pressure side surface and suction side surface of the airfoils, the blades including first blades and second blades interleaved about the rotor, the airfoil of the first blades having a first thickness distribution along the span defining a first natural vibration frequency of the airfoils of the first blades, the airfoil of the second blades having a second thickness distribution along the span of the airfoil defining a second natural vibration frequency different than the first natural vibration frequency, the first thickness distribution being different than the second thickness distribution along a radially-inner portion of the span, the first thickness distribution matching the second thickness distribution along a radially-outer portion of the span extending from a 50% span position to a 100% span position, the first and second thickness distributions having a maximum thickness (t-max′) at the root of the airfoils located at a first position on the chord, and the first and second thickness distributions having a maximum thickness (t-max″) at the tip of the airfoils located at a second position on the chord different than the first position, wherein a Δt-max is the difference between the maximum thickness of the airfoil of the first blades and the maximum thickness of the airfoil of the second blades, and the Δt-max is largest at a 0% span position of the airfoils of the first and second blades.

A method of forming a rotor of a gas turbine engine, the method comprising:

• providing first blades and second blades, the first blades having a first thickness distribution defining a first natural vibration frequency, the second blades having a second thickness distribution defining a second natural vibration frequency different than the first natural vibration frequency, the first thickness distribution being different than the second thickness distribution along a radially-inner portion of the first and second blades, the first thickness distribution matching the second thickness distribution along a radially-outer portion of the first and second blades extending from a 50% span position to a 100% span position, the first and second thickness distributions having a maximum thickness (t-max′) at a root of the first and second blades located at a first position on a chord of the first and second blades, and the first and second thickness distributions having a maximum thickness (t-max″) at a tip of the first and second blades located at a second position on the chord different than the first position, and defining a difference between the maximum thickness of the first blade thickness distribution and the maximum thickness of the second blade thickness distribution being defined as Δt-max, the Δt-max being largest at a 0% span position of the airfoils of the first and second blades;
• positioning at least one of the second blades relative to a hub of the rotor to be circumferentially between two of the first blades;
• and
• fastening the first and second blades to the hub.