a hollow fan blade for turbo fan gas turbine engines is formed of two separate detail halves . each detail half has a plurality of cavities and ribs machined out to reduce weight . these detail halves are subsequently bonded and given an airfoil shape in the forming operation . the present invention provides a hollow fan blade with internal cavity and rib geometry with improved durability that permits the bonding and forming to be performed without the need for gas pressurization . the ability to form the hollow fan blade of the present invention without gas pressurization is a result of the cavity and rib geometry and the orientation of the ribs . the ribs are tapered and transition into a compound radius of the floor that simulates the classical arch design element . the orientation of the ribs is generally in a parallel plane with the load vector that results from forming loads during the pre - form and final form operations . this orientation provides compressive stress transfer into the ribs and away from the concave and convex skins . the rib spacing is controlled where ribs can not be held in a parallel plane with the load vector .