Loop yoke for proprotor systems

A 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:
• a continuous loop having first and second longitudinal sections extending between inboard and outboard arcuate sections;
• a flapping bearing receiving region disposed at least partially within the inboard arcuate section to an interior of the continuous loop;
• and
• a centrifugal force bearing receiving region disposed at least partially within the outboard arcuate section to the interior of the continuous loop;
• and
• a plurality of bearing assemblies, each disposed within one of the continuous loops and each including:
• a flapping bearing received by the flapping bearing receiving region of the respective continuous loop and coupled to the hub;
• a lead-lag damper coupled to the hub;
• a centrifugal force bearing received by the centrifugal force bearing receiving region of the respective continuous loop;
• 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;
• wherein, each of the continuous loops comprises a composite material having a plurality of double bias material plies and a plurality of unidirectional material plies;
• and
• wherein, the number of unidirectional material plies is greater than the number of double bias material plies.