marcelh wrote:Question remains why this wasn’t figured out before. The fuselage-wingbox interface is an essential structural part and I would presume it was designed with great care. It will be corrected and the 77X will be flying asap, but why haven’t they designed it right in the first place?
"Unknown unknowns" are by their very nature, unknown.
As SEPilot noted up-thread, if the OEMs could perfectly model everything in a computer using Finite Element Analysis, there would be no need for a flight test or certification program. The first frame would receive it's Type Certificate pro forma as it is being assembled and after it's first OEM and customer acceptance flights, be delivered directly into service.
But the OEMs can't model that accurately as of yet, so they're required to "show their work" via testing and when they fail, they are required to fix the issue and show the fix corrected the issue. Only then do they get their certification.