AA B757 Exp. Decompression, FL310 due 1' x 2' hole in fuselage
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PaperTiger:
The 757 uses the same "barrels" as the 707.
To be really picky, the 767 isn't a wide body either. It's a twin-aisle with just one extra seat per row (Y) vis-a-vis the narrow bodies.
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As an engineer, I am impressed with the radii on the corners of the crack. Heck, I am lucky if I send out a part designed like that and I can get the supplier to match such a nice radius in a corner. I am afraid if I was a passenger in front of business class and this happened, after things settled down I would by itching to get a look at the fracture surfaces.
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As an engineer, I am impressed with the radii on the corners of the crack. Heck, I am lucky if I send out a part designed like that and I can get the supplier to match such a nice radius in a corner.
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Rapid or explosive, Have you ever dumped a cabin at max Dp out your slow moving outflow valve? I estimate a explosive 12" by 24" (larger than than your out flow valve for type) would give every passenger a bad f-ing hair day real quick!.
And the difference between 'explosive' decompression and 'rapid' decompression remains significant...'rapid' = bad hair day.... 'explosive' can equal last day worrying about your hair...
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Is the area where the blowout happened one that is particularly highly stressed in some relatively rare circumstances? The skin wrinkles received by a B767 at Bristol a few weeks ago seem to have been in the same general area, and the thread about that incident refers to two other cases of repairs in similar places, one to the same airframe. These were B767, rather than B757, and I don't know how closely the design teams for these bits of similar products worked. But twice is coincidence, three times is ...
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Example of chemically milled fuselage skin panel:
For info on chemical milling of aluminum, check out pages 368-370 of Aluminum and Aluminum Alloys by J. R. Davis & Associates.
For info on chemical milling of aluminum, check out pages 368-370 of Aluminum and Aluminum Alloys by J. R. Davis & Associates.
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I would like to add a couple of comments to this thread.
One point is with the reference to the WSJ article, it does not state the aircraft had less than 25000 flight hours, the figures were for the number of flights.
What l can remember with regards to using the same flight barrels as the B707, the skin thickness on the B757 is a lot thinner, hence the special type of rivets used.
One point is with the reference to the WSJ article, it does not state the aircraft had less than 25000 flight hours, the figures were for the number of flights.
What l can remember with regards to using the same flight barrels as the B707, the skin thickness on the B757 is a lot thinner, hence the special type of rivets used.
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Mr @ Spotty M:
I have to learn to read. 
Nonetheless, the article went on to say that is not a high-time/cycle airframe.
One point is with the reference to the WSJ article, it does not state the aircraft had less than 25000 flight hours, the figures were for the number of flights.
Nonetheless, the article went on to say that is not a high-time/cycle airframe.
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10 year history on chem milled sheets
In addition to this newest AD for Southwest - 2010-01-09 Link > The Boeing Company Model 737-300, -400, and -500
It is hardly the first. A 2004 AD refers to a Alert Service Bulletin dated Dec 14, 2000.
2004-18-06, 737-200, -200C, -300, -400, and -500 series airplanes, as listed in Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; certificated in any category. Effective Date;October 13, 2004. To find and fix fatigue cracking of certain upper and lower skin panels of the fuselage, which could result in sudden fracture and failure of the skin panels and consequent rapid decompression of the airplane. Inspections, repairs, and preventive modifications done before the effective date of this AD per Boeing Alert Service Bulletin 737-53A1210, dated December 14, 2000, are acceptable for compliance with the corresponding actions required by this AD.
See Link for full text > Boeing Model 737-200, -200C, -300, - 400, and -500
Then in 2008 >
2008-12-04. 737-600, -700, -700C, - 800, and -900 Series Airplanes SUMMARY: We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD requires various repetitive inspections to detect cracks along the chemically milled steps of the fuselage skin or missing or loose fasteners in the area of the preventative modification or repairs, replacement of the time-limited repair with the permanent repair if applicable, and applicable corrective actions if necessary, which would end certain repetitive inspections. This AD results from a fatigue test that revealed numerous cracks in the upper skin panel at the chemically milled step above the lap joint. We are issuing this AD to detect and correct such fatigue-related cracks, which could result in the crack tips continuing to turn and grow to the point where the skin bay flaps open, causing decompression of the airplane. This AD is effective July 16, 2008.
This AD applies to Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-53-1232, dated April 2, 2007.
See Link for full text Boeing Model 737-600, -700, -700C, - 800, and -900
It is hardly the first. A 2004 AD refers to a Alert Service Bulletin dated Dec 14, 2000.
2004-18-06, 737-200, -200C, -300, -400, and -500 series airplanes, as listed in Boeing Alert Service Bulletin 737-53A1210, Revision 1, dated October 25, 2001; certificated in any category. Effective Date;October 13, 2004. To find and fix fatigue cracking of certain upper and lower skin panels of the fuselage, which could result in sudden fracture and failure of the skin panels and consequent rapid decompression of the airplane. Inspections, repairs, and preventive modifications done before the effective date of this AD per Boeing Alert Service Bulletin 737-53A1210, dated December 14, 2000, are acceptable for compliance with the corresponding actions required by this AD.
See Link for full text > Boeing Model 737-200, -200C, -300, - 400, and -500
Then in 2008 >
2008-12-04. 737-600, -700, -700C, - 800, and -900 Series Airplanes SUMMARY: We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes. This AD requires various repetitive inspections to detect cracks along the chemically milled steps of the fuselage skin or missing or loose fasteners in the area of the preventative modification or repairs, replacement of the time-limited repair with the permanent repair if applicable, and applicable corrective actions if necessary, which would end certain repetitive inspections. This AD results from a fatigue test that revealed numerous cracks in the upper skin panel at the chemically milled step above the lap joint. We are issuing this AD to detect and correct such fatigue-related cracks, which could result in the crack tips continuing to turn and grow to the point where the skin bay flaps open, causing decompression of the airplane. This AD is effective July 16, 2008.
This AD applies to Boeing Model 737-600, -700, -700C, -800, and -900 series airplanes, certificated in any category; as identified in Boeing Special Attention Service Bulletin 737-53-1232, dated April 2, 2007.
See Link for full text Boeing Model 737-600, -700, -700C, - 800, and -900
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Green Guard:
The hammer effect is where a hole develops, the entire air mass in the fuselage starts moving towards the hole and then suddenly the hole is blocked. You can hear it in water pipes when a valve suddenly shuts, but it can happen with a compressible medium such as air as well. There will be a pressure spike which, if the container holds, will dissipate safely. If it exceeds the material strength of the container then it will rupture.
The alternative Aloha 243 incident was that this happened - the outflow started, the flight attendant got sucked into the hole and got stuck, then the excess pressure ripped the rest of the fuselage off, fracturing at weak points all around. I suspect the NTSB version would have it that everything started and propagated from one place.
So, no hole, no hammer. (
"Hammer effect" exists as much as "Air Pockets"
Also...why this hammer is not active before the hole appeared ?
Also...why this hammer is not active before the hole appeared ?
The alternative Aloha 243 incident was that this happened - the outflow started, the flight attendant got sucked into the hole and got stuck, then the excess pressure ripped the rest of the fuselage off, fracturing at weak points all around. I suspect the NTSB version would have it that everything started and propagated from one place.
So, no hole, no hammer. (
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I don't see how the flight attendant could block the initial hole (causing a fluid hammer effect) with all the fuselage structure (frames, ribs and stringers) and cabin decorative panels in the way.
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airframe fatigue depends entirely on flightcycles, not on airframe hours. I have worked on Fokker 100 with 49000hours/41000cycles but also on B747 with 101000 hours/12000cycles. in calander age the boeing was newer, but in airframe life the fokker is 4 times older.
For years there have been structural mods on lapjoints on Boeing, especially the 737 series (good little earner), most of them come to light during ageing aircraft inspections.
But still there are people in the trade who think it's not a problem to use stanley blades and the like on a pressurised hull.....
For years there have been structural mods on lapjoints on Boeing, especially the 737 series (good little earner), most of them come to light during ageing aircraft inspections.
But still there are people in the trade who think it's not a problem to use stanley blades and the like on a pressurised hull.....
