Abstract: A preform of a superplastically formed fan blade for a turbofan aeroengine, includes two blade flank components and a core sheet sandwiched between them. A manufacturing process for producing the blade preforms comprises cutting titanium plate material into rectangular prism shaped pieces of suitable length and thickness. Each piece is cut lengthwise along an inclined plane to form two separate tapered panels which become the blade flank components. After machining to a three dimensional profile on the cut faces, pairs of the blade flank components are stacked together with their uncut surfaces confronting each other, the core sheet being placed between them. The blade flank components are then diffusion bonded to the core sheet in a predefined pattern so as to create the blade preform with an internal structure defined by the bonding pattern. The blade preform can then be superplastically formed and finish machined to produce the fan blade.