747400sp
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How Well Built Are 737's

Mon Jan 24, 2011 4:33 am

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?
 
UAL747
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RE: How Well Built Are 737's

Mon Jan 24, 2011 5:05 am

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
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alasizon
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RE: How Well Built Are 737's

Mon Jan 24, 2011 6:00 am

The first aircraft of the A320 family were built before the first B737NGs, so in theory the A320 family is actually older.
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737tdi
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RE: How Well Built Are 737's

Mon Jan 24, 2011 7:54 am

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]
 
nomadd22
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RE: How Well Built Are 737's

Mon Jan 24, 2011 3:01 pm

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".
Anon
 
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bikerthai
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RE: How Well Built Are 737's

Mon Jan 24, 2011 6:35 pm

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
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BMI727
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RE: How Well Built Are 737's

Mon Jan 24, 2011 6:40 pm

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.
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HAWK21M
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RE: How Well Built Are 737's

Mon Jan 24, 2011 6:50 pm

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
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b767
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RE: How Well Built Are 737's

Mon Jan 24, 2011 7:41 pm

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?
 
nomadd22
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RE: How Well Built Are 737's

Mon Jan 24, 2011 7:50 pm

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.
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RE: How Well Built Are 737's

Mon Jan 24, 2011 8:25 pm

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?
 
UAL747
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RE: How Well Built Are 737's

Mon Jan 24, 2011 8:46 pm

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?
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redflyer
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RE: How Well Built Are 737's

Mon Jan 24, 2011 10:02 pm

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]
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737tdi
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RE: How Well Built Are 737's

Mon Jan 24, 2011 10:24 pm

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.
 
Mender
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RE: How Well Built Are 737's

Mon Jan 24, 2011 11:01 pm

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.
 
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RE: How Well Built Are 737's

Tue Jan 25, 2011 2:55 am

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
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BMI727
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RE: How Well Built Are 737's

Tue Jan 25, 2011 5:36 am

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?
 
737tdi
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RE: How Well Built Are 737's

Tue Jan 25, 2011 6:36 am

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
 
tdscanuck
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RE: How Well Built Are 737's

Tue Jan 25, 2011 2:29 pm

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.
 
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bikerthai
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RE: How Well Built Are 737's

Tue Jan 25, 2011 2:45 pm

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 
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Mender
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RE: How Well Built Are 737's

Tue Jan 25, 2011 7:38 pm

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.
 
737tdi
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RE: How Well Built Are 737's

Tue Jan 25, 2011 8:29 pm

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.
 
ImperialEagle
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RE: How Well Built Are 737's

Tue Jan 25, 2011 10:55 pm

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!"
 
tdscanuck
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RE: How Well Built Are 737's

Thu Jan 27, 2011 2:04 am

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.
 
na
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RE: How Well Built Are 737's

Thu Jan 27, 2011 11:44 am

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.
 
maxpower1954
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RE: How Well Built Are 737's

Fri Jan 28, 2011 7:27 am

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 did Douglas on the Eight and Nine. I know of no in-flight airframe failure on these aircraft, but Boeing, Lockheed, Airbus and others have had several. Examples NWA 720 in 1963, BOAC 707 in 1966, Braniff BAC-1-11 1966, Lockheed Electra 1959, 1960, 1968 and 1971 to name just a few there, and Airbus at JFK in 2001 and Cuba in 2005. Russ Farris

[Edited 2011-01-27 23:38:55]
 
Boeing77W
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RE: How Well Built Are 737's

Fri Jan 28, 2011 6:11 pm

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 behind the six fancy screens, the 737 was just like a 707 in numerous ways...
 
TrijetsRMissed
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RE: How Well Built Are 737's

Sun Jan 30, 2011 5:21 am

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 classify them in the "tank" category. Historically, 732/733s have been more prone to metal fatigue than the DC9/MD80 or 727 types.

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

Are both not certified for 75k? Of which, I don't believe a frame from either type has met. In any event, there are components on 737NG which have longer intervals for required heavy maintenance or replacement.

http://www.boeing.com/commercial/aeromagazine/aero_15/costs_story.html

Quoting UAL747 (Reply 11):
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?

It's quite simple - we're talking about durability. There's no denying the durability of those 43 yr old DC9-30s that were just retired by DL last year..
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roseflyer
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RE: How Well Built Are 737's

Sun Jan 30, 2011 4:49 pm

Quoting TrijetsRMissed (Reply 27):

Are both not certified for 75k? Of which, I don't believe a frame from either type has met. In any event, there are components on 737NG which have longer intervals for required heavy maintenance or replacement.

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 maintenance programs, or re-qualification/redesign for enhanced reliability of parts.
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SEPilot
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RE: How Well Built Are 737's

Mon Jan 31, 2011 1:34 am

Aircraft designers have to balance durability with weight, and try and find the best balance between money spent on fuel and money spent on maintenance. The more metal in the airframe (assuming it's in the right places) the lower the maintenance costs, but also the more money spent every day for fuel. From what I have read the DC-9 (but not the MD-80) and the DC-8 were the ones built like tanks; the 707 was underbuilt and had significant problems, and the 727 was about right-I have not heard of any significant structural problems with it (if anyone knows of any, I'd like to know about them.) It seems that the 737 was reasonably good when it first came out, and both redesigns have improved it. We'll see if the NG's are as well-built as DC-9's were in another 40 years or so.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
474218
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RE: How Well Built Are 737's

Mon Jan 31, 2011 2:51 am

Quoting tdscanuck (Reply 23):
That was the cold bonded skins issue...it carried into some of the early -300's but it's long gone now.


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 lap joints" after line number 291.

The 727 and 747 also used the same "cold bonded lap joint" procedure and it was replaced with the "sealed lap joints" at line numbers 850 and 201 respectively.
 
TrijetsRMissed
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RE: How Well Built Are 737's

Sat Feb 05, 2011 9:38 am

Quoting SEPilot (Reply 29):
From what I have read the DC-9 (but not the MD-80) and the DC-8 were the ones built like tanks;



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 use of composites, which became standard on all MD-80 series from 1991. The MD-90 and 717 took the composites a step further - thus being the least overbuilt of the Douglas twins.
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b767
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RE: How Well Built Are 737's

Sat Feb 05, 2011 7:10 pm

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 structure.Also I thought the MD80 used the same thick skin and frame as the DC9 with the same distance between stringers.I belive it was also strenghten in some areas after the now famous landing test accident.Sorry for beeing a little away for the original topic.
 
nomadd22
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RE: How Well Built Are 737's

Sat Feb 05, 2011 8:33 pm

Quoting TrijetsRMissed (Reply 27):
Are both not certified for 75k? Of which, I don't believe a frame from either type has met. In any event, there are components on 737NG which have longer intervals for required heavy maintenance or replacement.
Quoting TrijetsRMissed (Reply 27):
I don't believe a frame from either type has met.

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 hair of that.
Anon
 
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litz
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RE: How Well Built Are 737's

Mon Feb 07, 2011 6:19 pm

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

This ought to be interesting ... the number of commercial aircraft that have "experienced" a military attack can be counted on fingers ... and probably only one hand's worth.

With the exception of the DHL aircraft, I'm not sure any have even resulted in anything other than a crash and total destruction.

I wonder if we'll ever see the results, or if they'll be classified ...

- litz
 
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SEPilot
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RE: How Well Built Are 737's

Fri Feb 11, 2011 5:56 pm

Quoting nomadd22 (Reply 33):
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 hair of that.

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 have each lasted longer.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
BMI727
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RE: How Well Built Are 737's

Fri Feb 11, 2011 8:55 pm

Quoting SEPilot (Reply 35):
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 have each lasted longer.

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 miles.

Quoting SEPilot (Reply 35):
the Classics and NG's I believe would have each lasted longer.

I think that Aloha found out that their newer engines did not take kindly to short flights and short turnarounds, having less time to warm up and/or cool down. AQ flew their -200s on their interisland flights until the day they went under as far as I know.
Why do Aerospace Engineering students have to turn things in on time?
 
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SEPilot
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RE: How Well Built Are 737's

Sat Feb 12, 2011 2:14 pm

Quoting BMI727 (Reply 36):
I think that Aloha found out that their newer engines did not take kindly to short flights and short turnarounds, having less time to warm up and/or cool down.

That may well be true; I was referring to the fuselages. But it goes to show that "progress" is not always beneficial to everybody.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
roseflyer
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RE: How Well Built Are 737's

Sat Feb 12, 2011 6:13 pm

Quoting BMI727 (Reply 36):
I think that Aloha found out that their newer engines did not take kindly to short flights and short turnarounds, having less time to warm up and/or cool down. AQ flew their -200s on their interisland flights until the day they went under as far as I know.

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 for the 737-200. However with that said, the systems and main moving parts of the 737NG are designed to fly more cycles than the original 737s. Design life is longer.

Quoting SEPilot (Reply 37):


That may well be true; I was referring to the fuselages. But it goes to show that "progress" is not always beneficial to everybody.

As I have said before, fuselage and structure are not the main parts that experience wear and tear that lead to failure or replacement on an airplane. It's the systems and moving parts that make the airplane function that see more effect. With that said, the fuselage is stronger on the 737NG as the skin and structure was strengthened so that the plane could have a max altitude of 41K instead of 37K like on the older 737 models.
If you have never designed an airplane part before, let the real designers do the work!
 
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SEPilot
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RE: How Well Built Are 737's

Sat Feb 12, 2011 7:04 pm

Quoting RoseFlyer (Reply 38):
As I have said before, fuselage and structure are not the main parts that experience wear and tear that lead to failure or replacement on an airplane.

But that was the problem with the Aloha 737. Granted, it was an extreme case and not at all typical.
The problem with making things foolproof is that fools are so doggone ingenious...Dan Keebler
 
737tdi
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RE: How Well Built Are 737's

Sun Feb 13, 2011 12:51 am

Quoting RoseFlyer (Reply 38):
As I have said before, fuselage and structure are not the main parts that experience wear and tear that lead to failure or replacement on an airplane. It's the systems and moving parts that make the airplane function that see more effect. With that said, the fuselage is stronger on the 737NG as the skin and structure was strengthened so that the plane could have a max altitude of 41K instead of 37K like on the older 737 models

You are right, BUT, the parts you speak of are time limited items, such as the engines, flap transmissions, pumps, generators, flight controls etc.. The fuselage/structure is basically the only component that is "replace or repair on failure".

737
 
474218
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RE: How Well Built Are 737's

Sun Feb 13, 2011 1:08 am

Quoting 737tdi (Reply 40):
You are right, BUT, the parts you speak of are time limited items, such as the engines, flap transmissions, pumps, generators, flight controls etc.. The fuselage/structure is basically the only component that is "replace or repair on failure".


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 aircraft have such major components "life limited".

On most aircraft those parts are "conditioned monitored".

[Edited 2011-02-12 17:13:47]
 
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kanban
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RE: How Well Built Are 737's

Sun Feb 13, 2011 1:33 am

Quoting 474218 (Reply 41):
I have never heard of any other aircraft have such major components "life limited".


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 than the 747...
 
474218
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RE: How Well Built Are 737's

Sun Feb 13, 2011 2:28 am

Quoting kanban (Reply 42):
I believe landing gear is such an item, however the thresholds are extremely high.


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 required overhaul.
 
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kanban
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RE: How Well Built Are 737's

Sun Feb 13, 2011 4:36 am

Quoting 474218 (Reply 43):
Once they are overhauled they can be reinstalled and are good til the next required overhaul.



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 perform a more in depth overhaul and inspection... a case where workplace jargon and fact deviate
 
474218
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RE: How Well Built Are 737's

Sun Feb 13, 2011 4:00 pm

Quoting kanban (Reply 44):
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 perform a more in depth overhaul and inspection... a case where workplace jargon and fact deviate



The following is the FAA terminology:

"Hard Timed". Overhauled at a specific interval to insure structural integrity. Example: Landing Gear, removed/overhauled and reinstalled every 6 to 10 years.

"Life Limited". Removed and discarded at a specific time. Example: Oxygen Generators, removed/replaced with new generators every 14 years.

"On Condition". Remains in place until they fail. Example: Hydraulic Pumps, no periodic maintenance is required.

"Condition Monitored". Inspected or tested periodically to detect a deteriorated condition. Example: Flap Ballscrews, periodic backlash checks required. If they pass test they remain in place.
 
737tdi
Posts: 1116
Joined: Sun Sep 02, 2007 10:05 am

RE: How Well Built Are 737's

Sun Feb 13, 2011 6:05 pm

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 course almost all components can be overhauled and returned to service. As far as flap transmissions/ballscrews on the 737 they are both "condition monitored and hard timed on the classic" as of yet I don't believe the NG has a hard time on the transmissions. You do have to remember that this is highly subject to AD's once the aircraft have been in service longer.

737
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: How Well Built Are 737's

Mon Feb 14, 2011 6:12 pm

Quoting 474218 (Reply 43):
Landing gear require periodic "overhaul" but they are not "life limited".

Yes, they are. For example, 737NG Maintenance Planning Data - Appendix H (Life Limited Parts): At 75000 cycles
-Discard Left Main Landing Gear including trunnion link, shock strut, drag link, torsion links, side strut, walking beam and reaction link.
-Discard Right Main Landing Gear including trunnion link, shock strut, drag link, torsion links, side strut, walking beam and reaction link.
-Discard Nose Gear including drag brace, shock strut and torsion links.

Quoting 474218 (Reply 43):
Once they are overhauled they can be reinstalled and are good til the next required overhaul.

They do have an overhaul interval (21000 cycles/10 years on the standard program) but you still have the life limit. Once you hit 75000 cycles you're done.

Tom.

[Edited 2011-02-14 10:13:24]
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: How Well Built Are 737's

Mon Feb 14, 2011 8:12 pm

Quoting tdscanuck (Reply 47):
Yes, they are.


There are exceptions to everything.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: How Well Built Are 737's

Mon Feb 14, 2011 8:27 pm

Quoting 474218 (Reply 48):
There are exceptions to everything.

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 disks...they're too highly loaded to be fail-safe or damage tolerant and still perform with reasonable weight. That only leaves you with life limited.

Tom.

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