Bill_H
Well Known Member
Look at the failure mode in the pic. The head of the bolt pulled open the tank. Now, with no head on the bolt, since the center section member ROTATES in this failure, a strong bolt with no head might still "grab" inside the section and not just come out of the hole. The result could then be the same as a bolt with a head. (So the less a strong bolt or pin projects inside the member (as seen looking forward), the better.) But a bolt that would either easily shear or easily bend would not pull forward with the rotating section and tear open the tank. In normal flight, the current bolt or replacement is just carrying a vertical load - it is not keeping the tank from moving appreciably forward or aft.