Warbird Information Exchange

And I worked around them in the past. Just don't recall ?? Been watching plane savers on youtube, and the wings installation.
Its very scary that there is no spar connection and just a small thickness angle iron flange top and bottom that hold the wings on. It is like wow what a moment and stress in that area. And under a high G pull out, just wow. Also I heard DC-3's have never had a structural failure so I guess it works, but still just doesn't look or seem very good.
Any good airframe people here to add something?

I believe the T-6/Harvard is of similar construction....Wing bolts to angles

C-130 outer wings attach in much the same manner. The proof is in the pudding!

...and it's certainly not 'angle iron'!

Interesting film showing assembly of wing , I read there are 328 bolts per side
https://secure.boeingimages.com/archive ... 8L1G2.html

Interesting film short. It appears that most of the film clips were done in 1939-40. A-20's and DC-3's on the Douglas production line in Inglewood.

The first scene shows the right wing of NC14996 a DC-3A for Panagra Airlines delivered 10/1939.

American Airlines Flagship Albany NC25671 is shown being towed to the line. she was delivered 03/1940.

The wing attachment must have been filmed much earlier as it shows the wing being attached to Braniff Airlines DC-2 NC13716. The method of wing attachment was similar on the DC-2 and DC-3.

C2j

There are 4 or 5 bolts on the spar on the T-6, along with those on the flanges. Never pulled a wing from the DC-3s that I had worked on, so don't know about them

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It’s not unusual for the majority (or all) of the stress to be carried in the skin. I once heard from a guy who was developing some sort of STC for the Cessna 182 that when he calculated loads on the outer wing panels he found that the skin did all the work and the ribs and spars were totally redundant from a structural point of view.

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I have heard the designers for the DC3 wing also moved over to North American and used a similar wing design for the Texans

The DC-3 wing structure was designed ...at least in part...by Jack Northrop. They were used in his Alphas and Gammas.

I don't believe he went to North American, but by the time the NA trainers were designed, the design would have been the current "state of the art" for the industry.

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PBY is about the same too, with a few on the inside, need a small guy to get in there...lol

That is exactly correct, John. Jack Northrop and his team came up with the multi-cell, "sparless" wing design in the Alpha and very successfully applied it to the Beta, the Gamma and the Delta. By the time the Gamma and the Delta were being built Northrop was a division of Douglas. Jack's engineering approach and concepts formed the foundation of many engineers who flowed out from Northrop into many other companies (Douglas, North American, Chance-Vought, Consolidated) and brought many of Northrop's ideas into wide usage in industry.

Back to the origins of the post, I think with a little research one could find hundreds of examples of successful aircraft designs using this same wing attach method.

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Ryan Pemberton
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There is the story of the dc2 and a half which is a good read
http://www.douglasdc3.com/dc2half/dc2half.htm

Angle iron is a descriptive term, I would think it is a steel angle fitting. And really wasn't the plane Hawkins and powers was flying in that crash, a C-130 if so proves that is a weak point because both wings failed at the same area at the same time.

If I was to design that area of the wing, I'm afraid there would be no allowance for a pay load or engines or fuel, but the wings would be very very strong.

That's not quite how I would have described that accident. We're talking about outboard wing attachments here, but the N130HP accident occurred when a fatigue crack in the center wing torque box caused the right wing to fail. That's not a weak point in any way, the maintenance regime for that airplane did not cover the specific use of that particular airplane. Any airplane's structure will fatigue, it is up to the maintenance programme to catch it before it eats away the excess strength of the structure, as it did here.

Back to the topic, I thought that the DC-3 wing attachments did include a couple of bolts that attach the spars to the center wing section, but I could be wrong. I know that the B-25 wings do have these, as I've tightened them.

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T-6 has 6 bolts on the spar, wing to center section

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