Southwest Airlines 737 damage in flight

Ruht-Roh...

Now how do you suppose they prove that was an isolated (1 time) mfg'ing error.

 

They won't and can't.
It was a case of loose holes.
During manufacturing inspection, not every single hole is measured.
The holes are measured by percentage sample lots over a wide area.

 

The mechanic is supposed to use a specific drill for the size of rivet to be driven. The hole for a 3/16th rivet should be drilled with a number 10 drill that is a few 10 thousandth larger than the rivet. That allows for rivet expansion while it is being driven. When drilling or reaming a hole for a fastener the drill or reamer should make only one pass once it is through the material and then withdrawn so that there will be no oversized holes. Somebody wasn't using the correct technique in drilling the holes in which the material failed.

 

That might have something to do with pushing one 737 out the door every 1 & 1/4 days.
Gotta make that schedule!!!
-------------------------Boeing isn't the only place where this is happening.

 

I remember watching this operation many times in the fuselage sub assembly area. They drilled holes as fast as they could, slapping clecos in behind them to hold the sheets and then the riveters pre loaded the holes with rivets and taped them in. On the inside, a bucker with a long gang bar bucked the rivets as they were driven one after the other in a never ending series of quick blasts. On the 707 and 727 there were never any problems. I have never heard of any problems with any of the following models until now and I think that it is an isolated incident.

 

I have been thinking about the structure in this area over the wing center section. The skins are from .051 to.063 in thickness if my memory serves me. They have countersunk 3/16 dia. rivets installed and the loads from fuselage bending, shear reversal, pressurization, and a bit of torsion are concentrated in the area. The full spectrum of loads is vast and beyond my knowledge but if the fasteners in the lap joints don't keep the skins stabile when reacting to the loads, it will fail. Just my personal and humble look at it.

 

Have the 737 fuselages always been made in KS and shipped to WA by train??

http://jetphotos.net/viewphoto.php?id=6135891

It looks like a large portion of the 737 is made by Spirit Aerosystems now.

http://www.spiritaero.com/Content.aspx?id=3619

 

Here is an NTSB Release on the investigation..

http://ntsb.gov/Pressrel/2011/110425.html

And a photo of the damaged area..

http://ntsb.gov/Pressrel/2011/images/SWA812_skin_fracture.jpg

 

Is there a better picture of the leading edge of the tear?

 

Not always but have been for a few decades now.

They also build the cockpit and first 500 inches of the forward fuselage section for the 777 there as well, though that comes in pieces because the diameter to too large for train travel.