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Yes, correct.
 
I suspect this to be a portion of the the two dorsal longerons, a critical fatigue hot spot. A single B-1B had 47 feet of this structure replaced by Boeing (Douglas Long Beach site) in the early 2010s IIRC. They were hand-built composite replacements and the airplane was grounded at Long Beach for over a year for the work.

https://boeing.mediaroom.com/2009-05-29-Boeing-Team-Rebuilds-B-1-Backbone-for-US-Air-Force
Just reading "replacing 47 feet of longerons" makes my A&P self cringe...

Are we sure there's not a Bone in the Boneyard we could bring back to flying status instead?
 
There is a link here or in the B-52 re-engined thread where we can see how they carefully strip all parts out of the airframe cautiously, pulling out rivets after rivets before 3D scanning, testing and reverse engineering the thing.

I can ensure you that with this method, plus a cautious re-integration strategy (that might involve new parts), you can end up very easily with something that got better structural behavior than the original parts or assembly.
We have 40 years of engineering advance where extensive engineering can be applied on all parts when that was often time consuming or unachievable before. Hence a better or equal design at the end.
The good sign is the money and the willingness to cross-share the experience with students, keeping them away from coffee/inflated experience internship that has a very disastrous effect on the industry.

No. This looks good.
 
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Hehe
Aerospace is at the fringe of engineering.
Remember that we did not have 3D at the time, meaning that everything, mostly, was 2D projected.

With often complex body curvature (yes, Aerospace is the sexy branch of engineering!), parts real shapes are sometime not perfectly reflected in the manufuring drawings and instructions. Yes. You read it correctly.

Then, what happens when you loose the experienced mechanics, welder or men in charge of hot shaping, cold bend a complex part, casted or not? You can loose the knowhow. Loose the mold, that were often hand trimmed or rectified with experience from the assembly lines, and it's even worst!

That's where the fun start for very experienced engineers with good mathematics and academics (I insist). Like that Belgian detective, you have to rebuild a manufacturing chain, often from scratch, that it can be rebuilt accurately. That's what the kids here are offered to do (with some instructor). It's a hell lot of fun where you learn at every step of the way like few of your colleagues will ever have the opportunity to experience.

Highly recommended!
 
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My problem lies in the ability to fabricate a consistent component. It should have been perfectly feasible to do things when they were produced, been making airliners of al types consistently so why not this one?
 
Perhaps the longeron(s) have some sacrificial material to deal with tolerance stack-up across three major fuselage modules? Or the fuselage could have been slightly "bent" over several thousand flight hours? I don't know.
 
My problem lies in the ability to fabricate a consistent component. It should have been perfectly feasible to do things when they were produced, been making airliners of al types consistently so why not this one?
I'm guessing tolerance stack between modules. Each set of modules is a little different, so to keep that outer mold line correct the longeron has to be custom matched to the modules.
 
My problem lies in the ability to fabricate a consistent component. It should have been perfectly feasible to do things when they were produced, been making airliners of al types consistently so why not this one?
Also, airliners are a simple tube, not an area-ruled complex compound curved nightmare.

I'd expect that the 2707 would have had the same issues.
 
I'm guessing tolerance stack between modules. Each set of modules is a little different, so to keep that outer mold line correct the longeron has to be custom matched to the modules.
Yes. That's where 3D CAD made most famously a big impact on reliability and cost. WYSIWYG is real (with the appropriate manufacturing tools and methods also in the chain).
 

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