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How Well Built Are 737's  
User currently offline747400sp From United States of America, joined Aug 2003, 3508 posts, RR: 2
Posted (3 years 6 months 1 week 3 days 1 hour ago) and read 7961 times:

Please forgive me if I have ask this question before.

Even though the 737 is Boeing plane to compete against the A320 or maybe even the E-190, it still was first built around the same era as the 707 and 727. Both the 707 and 727 was built like tanks, so I wounder, is a 737NG built like a tank, or are they built with new material?

60 replies: All unread, showing first 25:
 
User currently offlineUAL747 From , joined Dec 1969, posts, RR:
Reply 1, posted (3 years 6 months 1 week 3 days 1 hour ago) and read 7940 times:

Quoting 747400sp (Thread starter):
Both the 707 and 727 was built like tanks,

What makes you think that the 737 and 707 were built like tanks? They were definitely not made out of the strongest materials as those evolved over time....which leads me to....

Quoting 747400sp (Thread starter):
is a 737NG built like a tank, or are they built with new material?

Of course it's built with newer, lighter, and stronger materials.

UAL


User currently offlineAlasizon From United States of America, joined Apr 2007, 289 posts, RR: 0
Reply 2, posted (3 years 6 months 1 week 3 days ago) and read 7909 times:

The first aircraft of the A320 family were built before the first B737NGs, so in theory the A320 family is actually older.


Window seats may be over-rated, but I'll take a window seat on a DC9 anyday
User currently offline737tdi From United States of America, joined Sep 2007, 796 posts, RR: 1
Reply 3, posted (3 years 6 months 1 week 2 days 22 hours ago) and read 7867 times:
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Actually the 737NG is not built significantly different then classics as far as materials are concerned, materials are still 2024 and 7075 AL. for the most part. Frames/stringers/tie clips/ floorbeams etc. are still the same, wing and tail structures not significantly changed (again material wise). There are some technical differences in structural design that did change, but the same can be said all the way through the progression of the Classic. There are, structurally, many differences in design of the -200 through the final -300's. Not to go off topic but as far as being built like a tank, that woud be a DC-8, those things have some thick skin!!!

[Edited 2011-01-24 00:01:33]

User currently offlinenomadd22 From United States of America, joined Feb 2008, 1832 posts, RR: 0
Reply 4, posted (3 years 6 months 1 week 2 days 15 hours ago) and read 7661 times:

737s can go 100,000 cycles, which is pretty impressive compared to a 320.
But, the story goes "When the last 737 is sent to the boneyard a DC-9 will be there to pick up the crew".



Andy Goetsch
User currently offlinebikerthai From United States of America, joined Apr 2010, 2072 posts, RR: 4
Reply 5, posted (3 years 6 months 1 week 2 days 11 hours ago) and read 7542 times:

We will know if the current 737 are built like a tank after the Navy take some pot shots at one of the P-8A airframe.
They just completed static testing, and frame is designated for live fire test.

I would doubt that the NG are built with the same margins as the Classics. Overbuilding the airframe would put the 737 at more of a dis-advantage over the A320.

I bet when they re-did the 737 they tried to shave as much weight as they could to the airframe . . .

bikerthai



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently onlineBMI727 From United States of America, joined Feb 2009, 15719 posts, RR: 26
Reply 6, posted (3 years 6 months 1 week 2 days 11 hours ago) and read 7537 times:

Quoting UAL747 (Reply 1):

What makes you think that the 737 and 707 were built like tanks?

Older planes such as that were generally overengineered compared to current ones. That doesn't equate to being tougher, or safer, but was just due to older technology levels.

Quoting nomadd22 (Reply 4):
737s can go 100,000 cycles, which is pretty impressive compared to a 320.

That's pretty much only on paper. If an A320 operator wants to fly their planes to 100,000 cycles, Airbus will probably be more than happy to do the testing and paperwork to up the limits.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 7, posted (3 years 6 months 1 week 2 days 11 hours ago) and read 7530 times:

Quoting nomadd22 (Reply 4):
When the last 737 is sent to the boneyard a DC-9 will be there to pick up the crew".

Thats a fantastic qoute.......

On the topic.....Although the B737s have been on the scene for decades now.The B737NG is different from the rest in terms of improved technology & Aerodymamic improvements to Wing root fairings.The powerplant has improved over years.

The B707/727/737 section 41 is very much similiar.

Although I've seen a DC9 getting scrapped & it sure is a tough aircraft....
regds
MEL.



Think of the brighter side!
User currently offlineb767 From Norway, joined Feb 2008, 127 posts, RR: 0
Reply 8, posted (3 years 6 months 1 week 2 days 10 hours ago) and read 7487 times:

I heard one engineer said the NG was signifacnt tougher than the classic .I am no pro,so I cannot comment on that,but I am asking where all this extra weight come from.A 700 series is 6 tons heavier than a 300 series classic.Can all that extra weight come from the bigger wings,tailfin and lenghtened main legs?

User currently offlinenomadd22 From United States of America, joined Feb 2008, 1832 posts, RR: 0
Reply 9, posted (3 years 6 months 1 week 2 days 10 hours ago) and read 7477 times:

Building a plane with heavier, stronger components doesn't always make it tougher. The extra weight and rigidity can just increase loads in other areas and make things wear out faster. It's quite possible the 737NG made parts lighter and increased their reliability and longevity at the same time.


Andy Goetsch
User currently onlineBMI727 From United States of America, joined Feb 2009, 15719 posts, RR: 26
Reply 10, posted (3 years 6 months 1 week 2 days 9 hours ago) and read 7450 times:

Quoting b767 (Reply 8):
Can all that extra weight come from the bigger wings,tailfin and lenghtened main legs?

Part of it, yes. And the changes necessary to increase MTOW by 16,000 lbs.



Why do Aerospace Engineering students have to turn things in on time?
User currently offlineUAL747 From , joined Dec 1969, posts, RR:
Reply 11, posted (3 years 6 months 1 week 2 days 9 hours ago) and read 7424 times:

I think some of these ideas that the classics were stronger, tanks, etc., is just pure nostalgia and emotion. What are we talking about, survivability of a crash? Components not wearing out as quickly? What is a tank? What is over-engineered? Isn't that like saying a 1960's Caddy is built like a tank when you compare it to a 1990's Toyota Camry? I mean, in what sense? That if it plows into you, it's gonna hit you with a heavier blow?

User currently offlineredflyer From United States of America, joined Feb 2005, 4315 posts, RR: 28
Reply 12, posted (3 years 6 months 1 week 2 days 8 hours ago) and read 7351 times:

Quoting BMI727 (Reply 6):
Older planes such as that were generally overengineered compared to current ones. That doesn't equate to being tougher, or safer, but was just due to older technology levels.

I can't imagine they were "over-engineered" in an age that had aerodynamic engineers using state-of-the-art technology such as...slide rules. If they were overbuilt, it's only by sheer accident because they didn't have the technology to render them more efficient, or more efficiently built.

Quoting nomadd22 (Reply 9):
The extra weight and rigidity can just increase loads in other areas and make things wear out faster.

I'm reminded of the story I read a few years back about the BOAC 707 crash on Mt. Fuji back in the '60's. The analysis of the crash revealed that parts of the empenage that had separated showed stress fractures not related to the crash resulting in an AD and Boeing beefing up that part of the fuselage on the production line.

[Edited 2011-01-24 14:27:33]


I'm not a racist...I hate Biden, too.
User currently offline737tdi From United States of America, joined Sep 2007, 796 posts, RR: 1
Reply 13, posted (3 years 6 months 1 week 2 days 7 hours ago) and read 7316 times:
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I took the OP at his question, "built like a tank?", to me this relates to structure. Don't know if you know this but there have been significant modifications to the empanage since the NG came out. I don't remember the line no. change but about 6 years ago we replaced all of the elevators on our NG's due to AD's and about the same time we changed out all of the horiz. stab. to stab. centerbox mount hardware due to AD's. All was blamed on excessive vibration due to hard mounted engines. Just goes to show that even with all of the high tech cad programs not all structural problems can be seen or predicted. 737, built like a tank? Nope. Just built as a very reliable people mover. The NG is definately a better aircraft then the classic, like said above, better aerodynamics, better avionics, alot easier to troubleshoot common problems and definately better engines and pylons.

User currently offlineMender From United Kingdom, joined Feb 2004, 240 posts, RR: 0
Reply 14, posted (3 years 6 months 1 week 2 days 7 hours ago) and read 7268 times:

The NG differs from the classic in many way as has been said repeatedly above. One simple but effective improvement is the way the fuselage skins overlap. On the Classic they tend to trapped moisture and encouraged corrosion, they overlap the other way round on the NG to produce a better, more corrosion resistant joint whilst still using the same basic parts, just assembled better.

User currently offlineSpacepope From Vatican City, joined Dec 1999, 2903 posts, RR: 1
Reply 15, posted (3 years 6 months 1 week 2 days 3 hours ago) and read 7163 times:

Quoting bikerthai (Reply 5):
We will know if the current 737 are built like a tank after the Navy take some pot shots at one of the P-8A airframe.
They just completed static testing, and frame is designated for live fire test

USN purchased an ex-WN -300 for live fire tests (N324SW).

Link here:

http://www.navair.navy.mil/nawcwd/na.../2010/2010_03_p-3c_replacement.htm



The last of the famous international playboys
User currently onlineBMI727 From United States of America, joined Feb 2009, 15719 posts, RR: 26
Reply 16, posted (3 years 6 months 1 week 2 days ago) and read 7084 times:

Quoting redflyer (Reply 12):
If they were overbuilt, it's only by sheer accident because they didn't have the technology to render them more efficient, or more efficiently built.

That's pretty much exactly what it was.



Why do Aerospace Engineering students have to turn things in on time?
User currently offline737tdi From United States of America, joined Sep 2007, 796 posts, RR: 1
Reply 17, posted (3 years 6 months 1 week 1 day 23 hours ago) and read 7057 times:
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Mender: There have been relatively low incidences of corrosion in the skin laps of the classics as built. The problem has been in the stresses caused by cycles and cracking which then induces corrosion in the cracks, but not in the laps themselves. I believe the same will inevetibly be caused in the NG as well. I am a A&P/AMT who has worked on these airframes for decades and see the effects of cycles. Stretch a rubber band too many times and it will break!!! Fortunately with the Classics and NG's they have built in safes that prevent the continuance of the failure. So I guess it is a tank with reactive/built in protection??? JMO. Does anyone see my posts??? Just curious. Ya'll seem to read right over info. and make your own conclusions, when a person posts pertinent info.. Do you just read the topic then post your answer without reading the responses??? Just curious.


THX


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 18, posted (3 years 6 months 1 week 1 day 15 hours ago) and read 6955 times:

Quoting 737tdi (Reply 17):
Mender: There have been relatively low incidences of corrosion in the skin laps of the classics as built. The problem has been in the stresses caused by cycles and cracking which then induces corrosion in the cracks, but not in the laps themselves.

I think Mender may be thinking of the problem with the cold-bonded lap joints on very early 737's, which really was a build problem.

Quoting 737tdi (Reply 17):
I believe the same will inevetibly be caused in the NG as well.

Absolutely. Any metal airliner using aluminum primary structure will eventually get fatigue cracking in the fuselage. It's just a question of when.

Quoting 737tdi (Reply 17):
Does anyone see my posts???

Yes.

Quoting 737tdi (Reply 17):
Do you just read the topic then post your answer without reading the responses??? Just curious.

I obviously can't speak for others, but I read all the responses before posting anything. If I agree what was said, I generally don't further comment unless I think I've got something else to add though.

Tom.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2072 posts, RR: 4
Reply 19, posted (3 years 6 months 1 week 1 day 15 hours ago) and read 6945 times:

Quoting Spacepope (Reply 15):
USN purchased an ex-WN -300 for live fire tests (N324SW).

Yes, I remember that. But there is also this:

http://boeing.mediaroom.com/index.php?s=43&item=1589

"In September, the Boeing P-8A team will begin refurbishing S1 to prepare it for live-fire testing at Naval Air Warfare Center, China Lake, Calif."

Maybe they will be shooting at more than one plane. How fun!!!

Quoting 737tdi (Reply 17):
Do you just read the topic then post your answer without reading the responses???

737tdi,

Just a suggestion . . . If you break up your posting into "smaller" paragraphs, it would help some of us with bad eye sights and short attention span.   

I always found Tom's posting easy to read even though sometimes he can be long winded 

bikerthai 



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineMender From United Kingdom, joined Feb 2004, 240 posts, RR: 0
Reply 20, posted (3 years 6 months 1 week 1 day 10 hours ago) and read 6818 times:

Quoting 737tdi (Reply 17):
Mender: There have been relatively low incidences of corrosion in the skin laps of the classics as built. The problem has been in the stresses caused by cycles and cracking which then induces corrosion in the cracks, but not in the laps themselves

I'm speaking from hands on experience of early -200 airframes on which I carried out a few skin changes. I don't know if later -300's suffered less as I moved onto wide body aircraft.


User currently offline737tdi From United States of America, joined Sep 2007, 796 posts, RR: 1
Reply 21, posted (3 years 6 months 1 week 1 day 9 hours ago) and read 6782 times:
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Sorry about the ramblings. Once I get a thought going it just kind of flows through the fingers. I'll try to break up my points a little better in the future. Writing is not my strong point. LOL.

User currently offlineImperialEagle From United States of America, joined Jan 2006, 2529 posts, RR: 23
Reply 22, posted (3 years 6 months 1 week 1 day 7 hours ago) and read 6685 times:
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Quoting nomadd22 (Reply 4):
When the last 737 is sent to the boneyard a DC-9 will be there to pick up the crew".

Yes, and so it goes.  The -8's and -9's had a heavier structure.



"If everything seems under control, you're just not going fast enough!"
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 23, posted (3 years 6 months 1 week 4 hours ago) and read 6376 times:

Quoting Mender (Reply 20):
I'm speaking from hands on experience of early -200 airframes on which I carried out a few skin changes. I don't know if later -300's suffered less as I moved onto wide body aircraft.

That was the cold bonded skins issue...it carried into some of the early -300's but it's long gone now.

Tom.


User currently offlinena From Germany, joined Dec 1999, 10655 posts, RR: 9
Reply 24, posted (3 years 6 months 6 days 18 hours ago) and read 6251 times:

An aircraft engineer once said to me, the 737 is, while sturdier than a A320, even in its NG guise rather oldfashioned in details, he even compared it to a vintage car with a modern drivetrain.

25 maxpower1954 : The Convair 880/990 was REALLY built like a tank! Convairs military jet experience played a big part here. They used chemicaly milled wing skins, as d
26 Boeing77W : I was speaking to a TRI/TRE the other day who started his career on 707's, went through to the 747 etc. then came back to the 737NG. He said that behi
27 Post contains links TrijetsRMissed : As been said, the 737 is a well-built aircraft. The NG in particular has quite an impressive safety record. For the long lasting classic, I would not
28 RoseFlyer : I believe 737 classics were 75K, 737NG 80K, original A320 48K, later A320 models have gone up, but I'm not sure if that is just an extension of maint
29 SEPilot : Aircraft designers have to balance durability with weight, and try and find the best balance between money spent on fuel and money spent on maintenanc
30 474218 : Boeing 737 "cold bonded lap joint" problem was limited to the 737-100's and -200's models. The 737 "cold bond lap joints" were replaced with "sealed
31 TrijetsRMissed : The original MD-81,-82,-83 had an identical fuselage of the D95, with a 14 ft stretch and larger improved high-lift wing. The MD-88 introduced the us
32 b767 : How does use of composits in some parts of the aircraft make it less overbuilt? The newer MD,s still used the same material as before in their primary
33 nomadd22 : You're right. I was waxing a little theoretical. As far as I know, none have gone much past 90,000 cycles. The famous Aloha convertible was within a
34 litz : This ought to be interesting ... the number of commercial aircraft that have "experienced" a military attack can be counted on fingers ... and probab
35 SEPilot : Remember that the Aloha was a very old -200 that flew in a sea air atmosphere (very conducive to corrosion); the Classics and NG's I believe would ha
36 BMI727 : Not to mention that Aloha and Hawaiian's narrowbodies would rack up cycles like few others back then. Their longest segments were a just over 200 mil
37 SEPilot : That may well be true; I was referring to the fuselages. But it goes to show that "progress" is not always beneficial to everybody.
38 RoseFlyer : That is true for the CFM engines as they were intended for longer flights since 737NGs average about 900 miles per flight compared to about half that
39 SEPilot : But that was the problem with the Aloha 737. Granted, it was an extreme case and not at all typical.
40 737tdi : You are right, BUT, the parts you speak of are time limited items, such as the engines, flap transmissions, pumps, generators, flight controls etc..
41 474218 : Are you sure the engines, flap transmissions, pumps, generators and flight controls are "life limited" on the 737NG? I have never heard of any other
42 kanban : I believe landing gear is such an item, however the thresholds are extremely high. Some items are cycle limited as well. However the 737 has no more
43 474218 : Landing gear require periodic "overhaul" but they are not "life limited". Once they are overhauled they can be reinstalled and are good til the next
44 kanban : sometimes one's memory plays tricks on one... and again it could be we called it life limited not meaning one had to scrap, but that one had to perfo
45 474218 : The following is the FAA terminology: "Hard Timed". Overhauled at a specific interval to insure structural integrity. Example: Landing Gear, removed/
46 737tdi : You are right, I should have not used the term life limited. What I should have said was these components have scheduled replacement/repair limits. Of
47 tdscanuck : Yes, they are. For example, 737NG Maintenance Planning Data - Appendix H (Life Limited Parts): At 75000 cycles -Discard Left Main Landing Gear includ
48 474218 : There are exceptions to everything.
49 tdscanuck : Absolutely true in general but, as far as I know, landing gear on large jets isn't one of them. Large landing gear have the same problem as turbine d
50 474218 : I will have to agree with you, you work with it daily. Myself, I can only go by my experiences before I retired. Our "damage tolerant' studies, were
51 kanban : thanks Tom... didn't think my memory had slipped that much.. and I think you will find the same wording in 707,727, 747 maintenance manuals. One of t
52 474218 : Hydrogen Embrittlement is induced during the electroplating (cadmium, nickel, chrome) process. You don't normally have to look for it as it will exhi
53 Post contains images kanban : agreed.. and I got off on a tangent... had nothing to do with life limited... and I knew that...
54 737tdi : Wow: 474218: You won't back down and admit you were wrong and someone else was right. That would be ME. You changed the subject. Come on man. I'm not
55 474218 : I think I said Tom was "right".
56 Post contains images SEPilot : But I suspect that comparatively few aircraft see more than 75,000 cycles, especially since NW DC-9's are disappearing
57 delawareusa : The 737s all versions will be seeing more cycles then A32X, E170, etc.. Only the DC-9s might be better.
58 SEPilot : As I understand it, there is still no fixed life limit on airliners. If you are willing to do the necessary inspections and maintenance you can fly a
60 HAWK21M : Very True....Most Decisions are based on Not Economically being viable to carry out the needed Mods/Major checks. Also older Aging Aircraft have more
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