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How the Southwest 737 Fuselage Weakness Went Undetected

eklendi
 
... now the focus of federal investigators has shifted to a problem in the design and testing of this 737 model: Boeing has acknowledged that a particular joint failed much earlier than its engineers expected. And because they didn't anticipate trouble, the joint was not reviewed during the 737's inspections, so any cracks in the fuselage went unnoticed. (www.popularmechanics.com) Daha Fazlası...

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TTail
TTail 0
THE 64K question is, what are they going to do about it? reskin the airplanes during the D check?? make them do NDI more often?? put them out of service
crusader2009
crusader2009 0
All I know is I'm glad that a reputible magazine came to the defense of Southwest. I am one semester away from my MBA and my thesis is all about showing how Southwest is the most successful airline in history because of XYZ. The day after this incident occured I got an email from my professor basically asking what tricks do I have up my sleave thats going to help me save my thesis. I'm proceeding with the same argument becuase Southwest is STILL the most successful and I have added a little blurb about them voluntarily grounding planes before the AD came out. This further proves my argument that they are customer centered.
chalet
chalet 0
TTail I am not and aeronautical/structural engineer, what I am is a private pilot with a few early hours and also a civil engineer. I suspect that Boeing overestimated the capacity of the skin to withstand X number of hours and Y number of cycles of the 737 NG and 757. Reskinning?...mmmm. terribly expensive. By way of comparison the Airbus 320 family has not shown the same fuselage skin weaknesses -no holes have been reported- although they had one serious rudder composite problems with a 300 and a 310 aircraft that was able to land OK, and a few landing gear cracks in 330s and I guess 340s too.
wrapitup
John OLeary 0
Southwest has been reskinning older 737 at major overhaul. In that process it seems that they would have discovered/uncovered developing problems, but I've seen no mention.
chalet
chalet 0
A strange thought crossed my mind: If Boeing is having problems with aluminum fuselage skinsin spite that they have been building pressurized fuselage aircraft since the mid-50s, I wonder what might happen in the future when the composite fuselage skin 787s get old......
rxpilot
rxpilot 0
GA C210 Pilot. I am interested of John OLeary's comment. Since they were reskinning already, there's probably some maintenance document out there? As for crusader's thesis, you may want to add that Southwest doesn't build planes. Now Boeing vs. AirBus may be a tougher argument.
tjoneillMO
Tim ONeill 0
Former NTSB member and long time airline mechanic John Golia put it best in an interview on FoxNews shortly after the failure--paraphrasing he said, "We saw a small hole in a 737 in 2009, now we have a big hole, and the next one may be a smoking hole. The airplane is trying to tell us something". The interview was in the "outsourced maintenance to El Salvador" vein (which evidently did not occur with this aircraft) but John's comments are spot on.

I would think if there is a serious error in life estimation it would be seen in the airframe accelerated fatigue test articles. It's not like this is a new structure from a design standpoint. Metallurgical analysis should identify the actual cause of the failure which should be compared to the 2009 incident. Operating history and manufacturing records for the particular aircraft involved should also be reviewed.
chalet
chalet 0
Even accurate records showing that a particular aircraft flew for say 33,987 hours and had 23,865 cycles does not tell the whole story and the reason being that some planes are run harder -or "softer"- than others, this is determined how the pilots who flew it. Secondly there is the additional, or lesser, stresses inflicted on the airframe, skin included, due to weather, some airplanes had the good fortune to fly on average through better weather than others. Of course all airframe makers build into the design a certain safety factor but it is never 100% accurate. Two or three of the U.S. Air Force's F-15 disintegrated over the past couple of years due to fuselage break-up in flight. The Canadian Forces and I believe Australia's CF-18s and F-18s had to undergo fuselage strengthening procedures due to faster than acticipated fatigue. In sum, this is an almost exact science.
rxpilot
rxpilot 0
Seems to be happening more. I thought the 2009 plane was going to land on my 1500' in WV! It had decended rapidly and was preparing to land. Pilot or not...that was scary. My wife says, "our plane is 37 years old, is that something we need to worry about?" My answer was, Honey I'm 38. She responded, "My point exactly. My T210 is of course non-pressurized, but a highly utilized 1970's P210? What do you think? The only one I know to have broken was a strutted one by I think Stephen Crossfield, the legend. Sorry to throw a piston in the mix.
tjoneillMO
Tim ONeill 0
This is part of the reason why your 210 gets an annual inspection!

Hard to compare a 210 to a 737 to an F-15. I live in MO where the ANG F-15 broke up in flight and was not aware of more than one inflight breakup--this one got everyone's attention and the problem was fixed.

The problem with aircraft is that the safety factor is low to keep weight down compared to things like say highway bridges. Throw in hard landings, weather, turbulence, and "the real world" and even the best design can be compromised.

This is why we perform inspections on a scheduled interval--the idea is to find and fix things before they become hazardous. Some fatigue critical parts have mandatory retirement limits based on hours or cycles in service. As an industry we have evidently failed to detect hazardous cracking in at least two SWA 737s and one AA 757. The question now is why--shortened inspection intervals are prudent until more information is known--then there will probably be airworthiness directives to fix it.
Footplate
Ron Hamilton 0
Anyone read Nevil Shute's "No Highway in the Sky" recently?
ChezFunk
Mike Meyer 0
I haven't seen any mention of the Wright amendment, which inflicts countless cycles on Southwewst's airframes, for no good reason. Imagine if Southwest could use Love Field with no restrictions.
chalet
chalet 0
The Wright amendment is an insult to free enterprise and DFW does not need it anyway. Still these skin/structural issues are not Wright's fault, SWA bussiness model is based on countless cycles so the airline and Boeing have to solve this issue. In the same vein American and Boeing have the same obligaton in regards to the de-skinning of 757s. Hope all of this will be satisfactorily resolved.
tjoneillMO
Tim ONeill 0
I believe Wright is supposed to go away this year?
The irony of this is described this week in an article in Aviation Week--the FAA was trumpeting all the work done over the past 20 years relative to aging aircraft resulting from the Aloha 737 failure when the SWA roof blew. The SWA 737 barely qualifies as an "aging" aircraft at 15 years but this probably will be changing (as it should) unless these incidents are positively determined to be something other than undetected cracking which would indicate inadequate inspection intervals.
ChezFunk
Mike Meyer 0
A cycle is still a cycle. Yes they count on turns, but a lot of them would have been avoided.
lulu11
maxine siegler 0
I think that the question is more about Building the aircraft. I will say Kudos to the very experienced Pilots that landed safe and as far as SWA they are an amazing company with the focus always on safety. I do hope that the answers are found before another incident. I am confident that Southwest will do whatever it takes.
jaytcsd
jay thompson 0
How can the flying public find out the # of cycles an aircraft has?

@crusader2009 - I hope your grammar and spelling are better in your thesis than they are in your post.
chalet
chalet 0
@crusader2009 success is measured in many forms, what is you yardstic(s) that its stock went up whereas other's dipped. OK it is a valid one but there are others such as reputation/acceptance among passengers. In this area SWA should rate rather lowly, it is several thousand feet below the likes of Singapore Airlines, Cathay, KLM, etc.

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