A box frame hub arm structure is provided and includes a body having an outboard surface, which is disposable to abut with an inboard surface of an outboard arm of an aircraft rotor head, and lead/lag sides. The body is formed to define a first cavity, an aperture communicative with the first cavity through the outboard surface and second and third cavities. The second and third cavities extend outwardly in opposite lead/lag directions from the first cavity to the lead/lag sides.