Apparatus and methods for fabricating a helicopter main rotor blade include a compaction fixture for assembling and compacting blade subassembly components and a sheath spreading/insertion apparatus for spreading and inserting a leading-edge sheath onto the blade subassembly during the compaction process. The compaction fixture includes a lower assembly having a contoured upper airfoil nest mounted in combination with a support structure and an upper assembly having a pressure bag affixed in sealed combination to a contoured backplate affixed in combination to a structural support truss. The contoured upper airfoil nest includes a plurality of tooling pins for locating an upper composite skin in aligned combination on the contoured upper airfoil nest and a plurality of pusher pins for chordwise alignment of a spar assembly in the contoured upper airfoil nest. Spar stanchions affixed to the support structure provide spanwise alignment of the spar assembly in the contoured upper airfoil nest. With the upper and lower assemblies in locked combination, the pressure bag is pressurized to compact the assembled blade subassembly components. The sheath spreading/insertion apparatus includes a movable stanchion, upper and lower elongate carriage members mounted in synchronized movable combination with the stanchion, and a row of suction cups mounted in combination with each carriage member. Pneumatic cylinders are mounted in combination with the stanchion and the respective carriage members.