The existing method of assembling these parts as of 1997 is shown in
Figure 19-13. As mentioned above, this method is currently capable of
delivering completely satisfactory assemblies. However, it is a Type-2 process,
and the envisioned precision assembly process would be a Type-1.
The current method proceeds in several tiers, as shown in Figure 19-13.
The right-hand side of this figure traces, from bottom to top, the creation of
the FTB-Rib-FTE subassembly. The FTB and FTE are built as separate
subassemblies including their respective spars. The ribs are built up from
individual structural shapes. These shapes include parts called shear ties that
interface the ribs to the skins. The shear ties and ribs are joined by contacts,
and a fixture aligns the shear ties to each other and the ribs. The result is that
the ribs are enabled to help set the contour of the skin during final assembly.
The FTB, FTE, and ribs are placed in a fixture and joined. Ribs and FTE have