4 ms·

I happen to have quite a bit of first-hand knowledge about aerospace rivets. AMA.

by abtinf 3y ago

jillesvangurp 3y ago
Is this as much of a non issue as I think it is? I'm thinking non structural bits of aluminum fuselage having a few extra holes is embarrassing but probably easily fixed/painted over and not that critical. Not generally a reason to get all upset and replace the part. But kind of embarrassing to have on a new part (i.e. get a discount). I've been watching a lot of rebuild rescue on Youtube lately where a bunch of mechanics are trying to rebuild a decades old plane nicknamed the bird house (because birds were nesting in it for well over a decade and they got absolutely everywhere). That seems to involve a lot of rivets, usage of all sorts of power tools, cleaning up old lots of parts, and generally not being too delicate banging things back into shape. Massive project and makes you realize just how complicated even a relatively small plane is.
- abtinf 3y ago
  It depends on how pervasive the issue is. Is it just two slightly nonconforming holes, or is it random sampling that suggests many nonconformances? It is not really feasible to test an installed rivet without destructive testing, because usually we are talking about blind rivets, which are remarkably complex fasteners. Think of them more like "small, ultra-precise one-time use machines", not "nails". This is part of the reason aircraft have so many rivets: each rivet is often capable of supporting a substantial fraction of the load where it is installed (sometimes even the entire load), but we install a huge number of them. The fact that this defect was caught during what seems like normal inspection processes also moves it closed to being a "non-issue". Manufacturing defects happen all the time and liability is massive, so there are extensive inspection and quality regimes in place.
rossdavidh 3y ago
Your best guess: if we checked closely for this sort of thing on Airbus planes, would it be found? I'm guessing not, but then I'm wondering if I'm naive.
- abtinf 3y ago
  The article is light on details, only stating: "...a worker at a Boeing supplier flagged that two holes in the plane’s fuselage may not exactly meet specifications." This statement is missing the information needed to grasp the seriousness of the issue. For example, if 100% of holes inspected (very unlikely), then 2 nonconforming holes out of hundreds of thousands of rivet holes on large craft might be acceptable and possibly even within acceptable quality limits; however, if the inspection plan calls for random sampling of two holes anywhere on the fuselage, and both of them happen to be nonconforming... not good. Non-conforming rivet holes may have many underlying causes. Even if they are missed during panel fabrication, a nonconforming hole is likely to cause a rivet installation failure, which are likely to be caught by downstream quality control processes. If by "closely", you mean "check every single rivet hole on a large commercial aircraft", you are going to quickly discover just how difficult this problem is. The tolerances are extremely tight, the holes are very small, and you are often actually dealing with multiple holes and sealant layers (a rivet holds multiple sheets together). I would be stunned if any large aircraft on the planet has 100% perfect rivet preparation.

I happen to have quite a bit of first-hand knowledge about aerospace rivets. AMA.

by abtinf 3y ago

I happen to have quite a bit of first-hand knowledge about aerospace rivets. AMA.

Is this as much of a non issue as I think it is? I'm thinking non structural bits of aluminum fuselage having a few extra holes is embarrassing but probably easily fixed/painted over and not that critical. Not generally a reason to get all upset and replace the part. But kind of embarrassing to have on a new part (i.e. get a discount). I've been watching a lot of rebuild rescue on Youtube lately where a bunch of mechanics are trying to rebuild a decades old plane nicknamed the bird house (because birds were nesting in it for well over a decade and they got absolutely everywhere). That seems to involve a lot of rivets, usage of all sorts of power tools, cleaning up old lots of parts, and generally not being too delicate banging things back into shape. Massive project and makes you realize just how complicated even a relatively small plane is.

abtinf 3y ago
It depends on how pervasive the issue is. Is it just two slightly nonconforming holes, or is it random sampling that suggests many nonconformances? It is not really feasible to test an installed rivet without destructive testing, because usually we are talking about blind rivets, which are remarkably complex fasteners. Think of them more like "small, ultra-precise one-time use machines", not "nails". This is part of the reason aircraft have so many rivets: each rivet is often capable of supporting a substantial fraction of the load where it is installed (sometimes even the entire load), but we install a huge number of them. The fact that this defect was caught during what seems like normal inspection processes also moves it closed to being a "non-issue". Manufacturing defects happen all the time and liability is massive, so there are extensive inspection and quality regimes in place.

rossdavidh 3y ago

Your best guess: if we checked closely for this sort of thing on Airbus planes, would it be found? I'm guessing not, but then I'm wondering if I'm naive.

abtinf 3y ago
The article is light on details, only stating: "...a worker at a Boeing supplier flagged that two holes in the plane’s fuselage may not exactly meet specifications." This statement is missing the information needed to grasp the seriousness of the issue. For example, if 100% of holes inspected (very unlikely), then 2 nonconforming holes out of hundreds of thousands of rivet holes on large craft might be acceptable and possibly even within acceptable quality limits; however, if the inspection plan calls for random sampling of two holes anywhere on the fuselage, and both of them happen to be nonconforming... not good. Non-conforming rivet holes may have many underlying causes. Even if they are missed during panel fabrication, a nonconforming hole is likely to cause a rivet installation failure, which are likely to be caught by downstream quality control processes. If by "closely", you mean "check every single rivet hole on a large commercial aircraft", you are going to quickly discover just how difficult this problem is. The tolerances are extremely tight, the holes are very small, and you are often actually dealing with multiple holes and sealant layers (a rivet holds multiple sheets together). I would be stunned if any large aircraft on the planet has 100% perfect rivet preparation.