Warbird Information Exchange

Spar bolts transfer vertical shear to the center section, skin flanges transfer tension and compression loads from wing bending across the skin joint.

The flanged joint requires a lot less precision in manufacturing and assembly.

Interesting topic - learning lots! I want the job of standing on the wing and hoisting myself and the wing up! I would guess this is loooong before OSHA.. . . .

Tom P.

I read somewhere that the early style wing NAA used on the BT-9/Harvard Mk I/NA-64 Yale (and Wirraway I suppose?) was essentially a scaled down DC-2 wing using the same NACA airfoils and similar construction methods.
NAA re-designed the outer wing sections to have less sweepback for the first BC-1A's/AT-6A's/SNJ-2's/Harvard Mk II's but retained the similar construction.

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The way I would do it is have a rectangular box in the center section that holds the engines and landing gear, with the long sides in vertical, and the wing spars would plug into the box section at maybe 4 to 6 feet deep. And that flange would have a lower leg that runs in the horizontal position that would be a minimum of 6 inches, the vertical flange would remain what they have for aerodynamic reasons and weight. The spar would only need 2 bolts per spar per wing in that box. The wing would have a minimum of 2 spars one front and one mid rear. Redundant from the stressed skin, yes, that is what you do with aircraft. Like 2 magnetos etc. There is never an excuse for wings to come off like that C-130 of Hawkins and Powers. It seems there is no lever effect bending the wings in normal cruise speed level flight so that DC-3 flange is not stressed much at all, but load the plane and fly it slow and pull out of a dive like the C-130 then you have wings bending, like on the Boeing wing bend test rig. I bet those DC-3 wings would not fare well on that test.
But then no DC-3 is supposed to ever have had a structural failure, so ????

There are few, if any, aircraft with such a long and illustrious history as the DC-3. I'd humbly suggest that even if you think you could do better, it's doubtful you could.

Talk is cheap; deeds take a bit more to demonstrate and the DC-3 design team has an 84-year head-start.

exhaustgases, I don't quite see where you want to go with your arguments? When you design and build your own aircraft, you can do that any way you want. But I would advise you to steer clear from redesigning existing, fully certified, types with excellent service histories.

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A Little VC10derness - A Tribute to the Vickers VC10 - www.VC10.net

The King Air uses 4 bolts per side to keep the wings on. Those 4 bolts are the only life-limited item on the primary structure of the airplane. Replace them at given intervals and the plane is good to go basically forever. I've seen the King Air used in some much more intense maneuvering than the C-130 and it's never had a wing failure, so there's something to be said for using bolts to keep the wings on.

BTW - as was pointed out above - the H&P C-130 accident wasn't the wing attach that failed, it was the center wing box, a known area of problem on the early C-130s. It's why the C-130Es were retired prematurely and why the USAF was so quick to get all the C-130H's that were converted from E's out of the fleet as quickly as they could get J models in - the wing boxes were cracking and you can only patch them up so many times.

In fact, that center wing box has been a problem for Lockheed on all of its military cargo aircraft. The C-141 had to have a redesign after cracks were found (fixed during the modification of the A models to C-141Bs and the new build B's). The C-5A production was stopped and the C-5B designed (and the A's "upgraded") because of center wing box cracks as well. So the lesson is - when in doubt, go Douglas.

Just trying to make things interesting that is all. I don't know much of anything about airframes. Its just something that doesn't look good to me. I know it works but still, kinda scary construction.