Low radius ratio fan for a gas turbine engine

A rotor assembly comprising:

• a rotor disk including an annular array of dovetail slots;
• an array of fan blades each having:
• a straight axial dovetail engaged in one of the dovetail slots of the rotor, an airfoil, and a transition section disposed between the dovetail and the airfoil, the fan blade having opposed pressure and suction sides, and further including first and second shoulders protruding from nominal surfaces of the pressure and suction sides, respectively, each shoulder including a boss defining a side face, and an upper section extending radially outward from the boss and tapering inward to join a nominal surface of the respective side of the fan blade, wherein a plurality of spaces are present between adjacent fan blades, and wherein the dovetail, airfoil, and transition section are formed as a composite layup comprising a plurality of layers of fibers embedded in a matrix;
• and
• an array of platforms disposed in the spaces between adjacent fan blades, each platform having an outer surface defining a portion of a flowpath boundary and abutting the side faces of the shoulders of adjacent blades.