Airliner construction

Paging Spasso!



Jedi

 

In fairly simple terms:

(On the 777)

No large spar goes through the center section that the wings bolt to.
Start first with the idea that the center section is NOT so much a fuselage component as it is a monocoque WING center section (box).

The wing center section is segmented into a series of compartments made out of machined and extruded webs. It is "skinned" just like a wing, only thicker.. The wings are indeed fastened to this center section but with many more points of attachment than the spars and wing to body fairings.

The wing center section actually mimics the cross-section of the wing root where the SPARS and ALL OF THE STRINGERS and the SKIN PANELS common to the top and bottom of the wing are attached. (Lots of titanium bolts)

The end result is two wings and the center section comprising a single and extremely strong unit that is then lowered into position between the forward and aft sections of the fuselage.

A side note: The wing center section is built with a fuselage center section attached on top, in the same area where the upper wing panels attach, using big "pickle fork" fittings adding even more strength.

In essence, this design is stronger than relying on just the spars to tie both wings together.
Another advantage is that the center section holds A LOT of fuel.

 

Spasso nailed it right on the head. I participated in the design of the wing center section ("lower section 45" in Boeing-speak) of the 767 while at Grumman, and that's the part of the aircraft that we built for Boeing. I saw the first shipset built at the plant in Stuart, FL and was very impressed with its solidity.

 

Jim, I must have worked very near you if you were in Everett on 767 body structures. I had a very nice Grumman fellow just in front of me who was designing the " pickle fork" installation. Boeing hasn't changed the basic wing joining concept since the 367-80. Some people call the center section the wing box, the center box, etc. but it is still the most "sturdily" item on the airplane where just about all the dynamic loads are concentrated.

 

Always have to have a smartypants kid in the family, he got it right on, though.

 

My lead was a young fellow named Garret Hull who seemed to be happiest on skis. He was on snow skis at Alpental every weekend in the winter and on water skis on the Columbia River at a place he had near George every weekend in the summer! My supervisor was the now-famous Bob Hammer whose gig nowadays is building new Messerschmitt Me 262s at the south end of Paine Field.

(I always thought that George, Washington was a goofy but fun name to call a town. Too bad they didn't have a sister town named Martha!)

 

Well, we had the same boss. I believe that there is a town(small) named Martha.

 

I forgot the disclaimer, "I AM NOT AN EXPERT"

 

I'm not either. The real experts are those who design the things that we observe and expound upon that make us sound like we are experts.BUT careful observation and a clear mind will give the observer an understanding of what the EXPERTS have done. Tomorrow I;ll have to figure out what all that gibberish means.

 

The older wings relied on two spar beams that carried the load individually and they were usually supported by struts. Then came the " D Tube" where the leading edge formed a load carrying tube that included the front spar. The modern jet liner wing has a spar box enclosed by the front spar, the upper skin, lower skin, and rear spar and stabilized by the ribs that maintain the contour of the wing and support the skins and stringers.The skins and stringers transmit the compression and tension loads of the wing as much as the spars so when the outer wing panels are joined to the center section, the connections are facilitated through the skins and stringers as much as the spars. As Spasso mentioned the three sections, the outer panels and center section when joined form a strong single unit.
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Like the stringers in the wing, my hands are getting stiff and the drawings aren't as good as they used to be but i still enjoyed adding a little to Spaao's excellent description.

 

I wish I could draw like that.
You could make money doing that................................

 

The keel beam shown, and some of its neighboring parts, was one of the items that I worked on during my stint on the 767 program in '79-'80. For any of you who know the layout of Boeing's Everett plant, this was in the newly-built 40-86 building.

 

Martha Lake with a little short paved strip, tall douglas firs at the end. Is that the "martha" you were thinking about?

I used to wire up that wing center section in final body join. Runnin' wires from the stick shaker clear to the toilet handle in the back; least that's what I used to tell folks when they asked what I did. Circa 1996-97

 

Tim, we must have read the same script because when people asked me what I designed on the airplane I told them that I designed the little man in the wheel well who turned off the light after the landing gear doors closed. Goes over big with the little kids.

 

Thanks for the kind words but that was a crude concept sketch. I am going to try to recover some of the copies of my work that WAS done on the board with pen and curves on mylar. That was almost 30 years ago and now starting with the 777 everything is on a computer screen and there are no drafting boards in sight. I have a large box filled with my old drafting equipment; pencils, pens, triangles, curves and sweeps, splines and ducks, templates, scales, and a little slide rule. An era and a skill long gone.

 

Today I saw 3 new fuselages on traincars going through Denver, I think they may have been 737's judging by the size. I've been in that area a lot of my life and at all times of the day and I have never seen that before. Anybody know anything about them?

 

I imagine that they WERE 737 fuselages on their way to Renton, Wa. from Wichita. Any day outside the Renton plant you can see a string of freight cars coming in with 5 or 6 737 bodies.

 

I assumed the lack of a carry through wing spar was designed in the event of the loss of or damage to a wing it wouldnt tear the center section and fusalage apart at the same time. In the same way the engines are designed to come off while doing minimal damage to the wing. Also the bottle pins that are the primary attachment of the wing to the center section allow for a somewhat flexable joint that give the wing an extra margin of flex while having minimal effect on the center section thus isolating the wing from the passenger compartment.

 

Only the old 737 uses bottle pins. All the others use the double plus chord Bob described in his drawings. 787 is a little different as there are no pickle forks at the rear spar and its a single plus chord with a "flex tee" bolted to the top. But having the center box and the two outboard wings are common across the Boeing product line. Which joint they do in what order is the only difference between them.

here is the wings and center box with the fuselage section being craned in to final body join on the 777F
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