I just had a nice dinner with my friend Larry Heagren who has been a career aeronautical engineer at Boeing. He's leaving soon to work Boeing's end of a contract with the Royal Air Force rebuilding CH-47 Chinooks. His prior projects include structures on the 767 and 737.
I brought Larry up to speed on the Main Spar Cap issue and showed him the engineering diagrams and pictures of unmodified main spar caps and mine. I explained that we might see some relief for some of the drilled main spar caps in the form of riveting the holes. Larry looked at the pictures showing the location of the holes in my main spar cap and had two observations: 1. The line of holes looks like it penetrates the extrusion and does not go cleanly through the thinnest part of the main spar cap. 2. Even if riveting were an approved fix, I don't pass the Boeing "2D" rule that every engineer knows. Basically take the diameter of the repair rivet and double it. If you don't have twice the diameter between the rivet and the edge of the structure, you have to do a full structural analysis to determine if the repair is safe. Larry's botton line was, "You ain't got enough meat between the holes and the edge of the main spar cap." Just a point worth noting if you have non-factory holes in the main spar cap. YMMV, Dave
