This is your Captain speaking....
Member
Joined: 03-05-2011
Posts: 37
From: Northeast Ohio
Did you see that they are saying that these flaws and cracks were easy to find when smoking was still allowed on planes?
Seems back when smoking was allowed the tobacco smoke would find and mark these tiny flaws where pressure was escaping with nicotene.
Who Knew?
Seems back when smoking was allowed the tobacco smoke would find and mark these tiny flaws where pressure was escaping with nicotene.
Who Knew?
Senior Member
Joined: 01-13-2008
Posts: 4,708
From: Washington State, where it rains
More like stress cracking. What alot of people dont know is alot of these failures are induced artificially and not from normal operating conditions. Take an airplane that went to the paint shop..multiple colors..lotsa tape and paper. The painters sometimes forget that running a razor blade across the metal surface, even slightly, leads to stress failure. As each flight goes thru press/depressurization the skin expands and contracts. Any nicks or 'scribe' lines on the surface will eventually fail and sometimes violently. Another source is scrapers used to remove sealant around panels and fairings.This stuff is tuff and is removed manually.If a metal scraper is used(which has been banned..cause for firing if caught),it can nick or score the surface which is why only plastic type scrapers are authorized for use. Think of it this way...glass acts the same way, score across a pane and tap it and it will break alone this line. Corrosion will also fatigue failures. Though in this case it was stated records show stringer clips have been replaced for cracking in this same area on this aircraft so it will be interesting to see where it goes. Boeing is quite thorough in their investigations.
Senior Member
Joined: 07-15-2009
Posts: 2,070
From: Waterbury CT
Not to save money, but WEIGHT...
737s are known for lap joint fatigue cracks. It's all in the design...
Where operators "save money" is farming out crucial repair work such as heavy overhauls of their aircraft to places like El Salvador, but that's corporate America these days
737s are known for lap joint fatigue cracks. It's all in the design...
Where operators "save money" is farming out crucial repair work such as heavy overhauls of their aircraft to places like El Salvador, but that's corporate America these days
Senior Member
Joined: 07-12-2006
Posts: 1,703
From: NE Ohio
More like stress cracking. What alot of people dont know is alot of these failures are induced artificially and not from normal operating conditions. Take an airplane that went to the paint shop..multiple colors..lotsa tape and paper. The painters sometimes forget that running a razor blade across the metal surface, even slightly, leads to stress failure. As each flight goes thru press/depressurization the skin expands and contracts. Any nicks or 'scribe' lines on the surface will eventually fail and sometimes violently. Another source is scrapers used to remove sealant around panels and fairings.This stuff is tuff and is removed manually.If a metal scraper is used(which has been banned..cause for firing if caught),it can nick or score the surface which is why only plastic type scrapers are authorized for use. Think of it this way...glass acts the same way, score across a pane and tap it and it will break alone this line. Corrosion will also fatigue failures. Though in this case it was stated records show stringer clips have been replaced for cracking in this same area on this aircraft so it will be interesting to see where it goes. Boeing is quite thorough in their investigations.
When the 737 was designed, composites for PRIMARY structural elements were not in use yet (at least for commercial aircraft).
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