Originally Posted by
scifi
Quote...
I know of one way in which these 12 Pads could be modified, to make a more secure structure, but I have no wish to help design anything for Boeing.
I can tell you as an aerospace engineer with over 40 years of structural design experience that the persons designing this door plug were not dummies and it was designed with specific elements performing specific functions and in doing so loads that were not anticipated could not be imparted to areas of the design where they weren't wanted.
Aircraft structure fatigue analysis consumes a tremendous amount of design and analysis time. To minimize the weight and maximize the life of a system such as this, it's important to isolate load paths so that you can accurately predict the loads and therefore predict the life of the part. I'm sure that to the uninitiated it is easy to say "if you do it this way it will solve the problem". But you and I don't have the knowledge of what the designer was trying to do here.
For example, you are proposing adding elements to try to trap the pads together and this defeats the whole purpose of the pad design. In this case the designer wanted to ensure that the only loads on the stop pads were outward pressure loads and the magnitude of those loads is known and understood. Adding elements to restrain the door using the pads would introduce potential upward or downward bending in those pad arms and to make sure that those were spread equally, you'd have to adjust all the clearance out of those restraints like you do for the outward restraining pads.
Moreover, differential thermal expansion between the door and the frame could result in some pad arms being bent in one direction while other arms could be bent in the other direction producing different combinations of arm bending loads that are impossible to know or determine.
This design undoubtedly went through a rigorous design review process and underwent significant structural analysis, and extensive testing before it was approved internally and finally certified. To assume that you know more than the folks who designed this and could easily do it better is the height of arrogance.