This how airbus wings attach to fuselage

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Twodeaddogs

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The difference is that Airbus techs will train on that particular fitting job until they can do it blindfolded, just like car assembly workers. You,as a homebuilder, really only want to fit a wing bolt once , instead of doing it every day for your day job. Also, Airbuses are full of sealant. Many bolts, nuts and every metal joint that is exposed to the outside world is covered in PR type sealant. Every joint. There's probably a ton of sealant in every A320. You really don't want to build a homebuilt that uses so much sealant as a percentage of the airframe weight,to fend off corrosion. Also, what I found in 30 years of aviation is that a lot of aircraft engineers have no interest in aircraft per se and will do just enough to justify a pay cheque. One of the things you really have to fight against in aircraft work is boredom and the enthusiasm and interest that homebuilders have is one of the best things about it.
 

wsimpso1

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Plenty of lessons there for hand-fitting homebuilt parts to precise tolerances.
I'm going to be a grammar gripe right here. We are talking airplane building here, so let's use the right words. Tolerances are variation allowed in parts or assemblies and are precisely specified on drawings. This video was almost all about fitting a wing to a fuselage. They positioned the wing using fixtures, fitted a bracket, drilled holes using fixtures. For the most part, tolerances were not in play. Change "precise tolerances" to "precisely positioned" and you might be right. But we saw nothing about their tolerances in the video.

There were most likely tolerances for sweep, dihedral, and angle of attack of the attached wing, and the fixtures were most likely schemed out to put the wing and fuselage relationship well within the tolerances intended for those angles. Probably they have some tolerances listed for the drilled hole diameter, and you can bet the fasteners have tolerances on every dimension on the part drawings. The workers shown fit the wing to the fuselage that way for the same reason we do in our little airplanes. They can not finish drill all of those holes ahead of time and have it all fit as well as it has to. Positioning of the holes would have to approach perfection way more closely than is practical in their shop. So they position the wing and fuselage, then finish each hole in both parts in one pass, and drive fasteners

So, precisely positioned and installed? Yes. Tolerances? We can only guess...

Billski
 

BBerson

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I think the bolts are fitted perhaps with an interference fit. So no actual allowable clearance.
I will ask a retired Boeing engineer.
 
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Matt G.

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I think the bolts are fitted perhaps with an interference fit. So no actual allowable tolerance.
I will ask a retired Boeing engineer.
Holes for an interference fit bolt still have a tolerance on the hole diameter, i.e. max/min hole diameter for that particular class of fit.
 

Angusnofangus

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I think the bolts are fitted perhaps with an interference fit. So no actual allowable clearance.
I will ask a retired Boeing engineer.
The wings of a 727 , and I assume other Boeing A/C, are secured with large 'bottle pins' . After preparation of the fittings that the pin goes in the pin is shrunk using liquid nitrogen and then inserted, After it warms up there is 0 clearance.
 
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wsimpso1

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I think the bolts are fitted perhaps with an interference fit. So no actual allowable clearance.
I will ask a retired Boeing engineer.
Maybe they were pressed into the holes. They were placed manually and then it looked like they were machine tightened against the nuts on the other side. Maybe that gadget both pressed them into the holes and tightened them, but even then, that would mean a pretty light interference, which also means a clearance on many with any reasonable holes size tolerance and fastener tolerance.

Rivets are supposedly upset to fully fill the hole and apply radial preload between rivet and hole as well as residual tension in the rivet and compression in the joined members. Go through the joint analytically and imagine setting the rivet to get these loads, then relieve the setting forces. The rivet and joined members unload a little elastically, get slightly longer in the direction of the hole axis, and some of the preload is lost. Is some still there or not? Go through the analysis and the joint keeps clamp load, but what radial preload you obtain in setting the rivet is largely lost when the setting forces go away.

Bolts and rivets mostly work by establishing clamp loads between the joined members. The joint has security only as long as the friction is larger than the active loads and the tensile loads do not open the joint. If active loads exceed friction or the joint opens and closes, the joint works and fatigue develops in the joined members and in the fastener. In the end, we need joints to be clamped securely against motion.

In rivets we feel a need for tiny clearance for install, then interference when assembled, even if it is largely lost in use. Why? First is that setting the first rivet centers the holes of the joined members, so we know finished locations match with where they were when we drilled them. Then rivets grab such a small amount of the joined members that we can not really stand to lose any area to a clearance hole. Bolt heads, washers, and nuts grab a bigger diameter chunk of the joined members, so clearance matters less with bolts. So we have microscopic assembly clearance, then the rivets are designed to fill the hole when set. And it works great when the design rules are maintained. Rivet spacing margins, min FOS of 4, etc. Similar for bolted joints. Violate those, like in the Cherokee flap system bolts connecting the shaft to bellcrank, and the joint can work, open the holes, and cost lots of money.

Billski
 

Dan Thomas

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Rivet spacing margins, min FOS of 4, etc. Similar for bolted joints. Violate those, like in the Cherokee flap system bolts connecting the shaft to bellcrank, and the joint can work, open the holes, and cost lots of money.
Light airplanes tend to use a lot of that sort of thing. Cessna uses it to attach the right/left rudder pedal brake bellcranks to the cross shafts, and those shafts are just thinwall tubing. The bolts can't be tightened much at all or you distort that tubing, and so they're constantly working against the side of that hole and wallowing it out. Cessna never intended these things to last 60 years or more, and owners hate being told that their "affordable" airplane needs a bunch of expensive parts. No such thing as a cheap old airplane.

Lake used the idea to attach their big hydraulically-actuate trim tabs--more accurately, they're auxiliary elevators--to their cross shaft, and the actuating bellcrank is also attached that way. The prop blast shakes those tabs and wallows out the holes quite quickly. One can't go drilling the holes out for the next size bolt, either. I was able to reduce the slop a lot on one airplane by measuring all the bolts we had in that size and picking out the ones with largest shanks. AN bolts will vary by a thou or better that way. Between that and the fact that the old bolts were also worn to a smaller diameter, the repair got the slop out. But not next time.
 

BBerson

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It might be nice to have bolts that can be squezzed or hammered like a rivet. Would need to be medium soft steel about 60k bolts or something, still twice as strong as 30k aluminum rivets. Tighten the nut and hammer it and then torque it again.
 

Dan Thomas

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It might be nice to have bolts that can be squezzed or hammered like a rivet. Would need to be medium soft steel about 60k bolts or something, still twice as strong as 30k aluminum rivets. Tighten the nut and hammer it and then torque it again.
Expanding steel could introduce radial stresses much too high for the aluminum structure, perhaps starting cracks.

A common aircraft fastener used in larger airplanes (and some smaller ones) is the Hi-Lock. The hole is drilled undersize, then reamed to an accurate, slightly undersized hole, and the fastener is drawn in by means of its nut, which has the hex on a machined neck that breaks off when the right torque is reached. No radial slop at all.

1614366244421.png
 

Angusnofangus

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Expanding steel could introduce radial stresses much too high for the aluminum structure, perhaps starting cracks.

A common aircraft fastener used in larger airplanes (and some smaller ones) is the Hi-Lock. The hole is drilled undersize, then reamed to an accurate, slightly undersized hole, and the fastener is drawn in by means of its nut, which has the hex on a machined neck that breaks off when the right torque is reached. No radial slop at all.

View attachment 107988
Interference fit for Hi-Loks is usually .001 to .0015, depending on the thickness of the material. Occasionally a transition fit is called for where the hole is the same size as the Hi-Lok, generally for really thick material.
 

BBerson

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Expanding steel could introduce radial stresses much too high for the aluminum structure, perhaps starting cracks.

A common aircraft fastener used in larger airplanes (and some smaller ones) is the Hi-Lock. The hole is drilled undersize, then reamed to an accurate, slightly undersized hole, and the fastener is drawn in by means of its nut, which has the hex on a machined neck that breaks off when the right torque is reached. No radial slop at all.

View attachment 107988
I think that drawing in might also work with a grade 5 bolt. Then cut off the extra threads with a 4" abrasive wheel.
 
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