Soft-in-plane proprotor systems

A tiltrotor aircraft having a helicopter mode and an airplane mode, the tiltrotor aircraft comprising:

• a fuselage;
• a wing extending from the fuselage;
• at least one drive system supported by at least one of the fuselage and the wing;
• and
• at least one soft-in-plane proprotor system coupled to the drive system, the proprotor system including:
• a hub;
• a plurality of proprotor blades coupled to the hub such that each proprotor blade is operable to independently flap relative to the hub about a flapping axis, independently change pitch about a pitch change axis and independently oscillate in-plane about a lead-lag axis;
• a plurality of loop yokes, each coupling one of the proprotor blades with the hub and each including first and second longitudinal sections extending between inboard and outboard arcuate sections;
• and
• a bearing assembly disposed between the inboard and outboard arcuate sections of each loop yoke, each bearing assembly including:
• a flapping bearing disposed generally within the inboard arcuate section of the respective loop yoke and coupled to the hub;
• a lead-lag damper coupled to the hub;
• a centrifugal force bearing disposed generally within the outboard arcuate section of the respective loop yoke;
• and
• a blade anchor positioned between the lead-lag damper and the centrifugal force bearing, the blade anchor coupled to the respective proprotor blade between the lead-lag damper and the centrifugal force bearing such that the respective lead-lag axis is disposed within the respective proprotor blade.