FAA grounds all B-17E,F, & G models

[GeeRam]

A tapered spar tube?

There are several ways to produce a tapered tube, on any scale.

If the tube, be it steel or of some interesting aluminum alloy, is ductile enough, it cam be run into a gigantic "sizing" die, or "spun" with traveling dies", squeezing the parallel tube into a "conical" tube. This process will ado elongate the tube, in much the same way the starting blanks for hammer-forged barrels "stretch" as they are hammered.

NOT ALL ALLOYS are equal. Choose wisely and get opinions from several actual metallurgists.

IF the spar is readily removed and replaced, IFF replacements are available, then do it.

Failing that; perpetual hangar queens. Wreckage-strewn craters are a "different" sort of "interesting".

The tubes are constant OD, with an internal taper reducing the ID over part of the length, which is why 20 years of investigation has drawn a blank to getting them remade in the correct material that is commercially viable for the amount required.
There has been a lot of investigation done on this by the various B-17 restoration specialists, and they've drawn a blank.

[echo1]

It was bound to happen. These old birds can't fly forever.
Remember the N9M catastrophe. Last survivor of 4 built, and now gone, along with a seasoned pilot. My son and I were able to see it at the Chino Air Museum on a father son trip 1999.

2019 Northrop N-9M crash - Wikipedia

Saw the pilot and mechanic working on this ship in Chino the week before he augured in. We were at Fontana for NASCAR. PAX

[Sapper740]

Over the decades I've been privileged to see Evergreen, Sentimental Journey, Nine-0-Nine, Aluminum Overcast, Texas Raiders, Thunderbird, and of course, Chuckie.