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readytotaxi
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Limited Life Time Of Aircraft

Tue Aug 03, 2010 7:19 pm

As all aircraft have a limited life, I wonder how long it will be before a A380 will be parked up?
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EMBQA
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 7:38 pm

Quoting readytotaxi (Thread starter):
As all aircraft have a limited life

Aircraft do not have a limited life as long as you continue to maintain them. The life ends when it becomes more expensive to maintain them.
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JBo
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 8:51 pm

Quoting EMBQA (Reply 1):
Aircraft do not have a limited life as long as you continue to maintain them. The life ends when it becomes more expensive to maintain them.

Precisely. However, it is noted that some aircraft were designed and built to withstand a certain number of cycles, beyond which the performance/reliability is not guaranteed.

Some aircraft are built more ruggedly than others, which is why some on this board believe the DC-9 will be the only airworthy aircraft after the apocalypse  
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474218
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 9:21 pm

Quoting JBo (Reply 2):
Precisely. However, it is noted that some aircraft were designed and built to withstand a certain number of cycles, beyond which the performance/reliability is not guaranteed.


All current passenger aircraft a "design life goal" a specific number of cycles (one takeoff one landing = one cycle). A the time the "design life goal" is attained the manufacture is required to have an approved program that when incorporated will allow the operator to operate the aircraft beyond the "design life goal".

Some operators my choose to remove aircraft from their fleet before the "design life goal" is met to forgo the expense this added maintenance will require. However, many operator will incorporate these modifications and continue to operated the aircraft until they determine that it is no longer cost effective to continue provide the added maintenance required to continue the aircraft's airworthiness.
 
flyby519
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 9:39 pm

An idea what the "design life goal" for the ERJ 135/140/145 series is? There are some older ones getting up over 30k cycles.
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CanadianNorth
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 9:52 pm

Life limit of most aircraft is, as said, basically the point at which it becomes more expensive to keep it airworthy than it would be to replace it.

Quoting flyby519 (Reply 4):
There are some older ones getting up over 30k cycles.


I know it's an apples to rear differentials comparison, but we have a 737 in our fleet still going strong with over 70k cycles (and age doesn't matter nearly as much as some people think, we have several aircraft that are multiple years older than it with significantly less cycles)


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474218
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 10:26 pm

Quoting flyby519 (Reply 4):
An idea what the "design life goal" for the ERJ 135/140/145 series is? There are some older ones getting up over 30k cycles.


They were not included as their MTOW is under 75,000 lbs.
 
atlengineer
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RE: Limited Life Time Of Aircraft

Tue Aug 03, 2010 10:55 pm

Quoting CanadianNorth (Reply 5):

If I remember correctly from Widgetheads, some of the Delta DC9-30's and 40's still flying are over 40 years old and have as much as 90,000 hours and/or 70,000 cycles on them. I'm flying PIT/ATL Thursday night on a DC9-50. That plane is probably 35 or more years old.

Barry
 
474218
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 1:06 am

Quoting atlengineer (Reply 7):
If I remember correctly from Widgetheads, some of the Delta DC9-30's and 40's still flying are over 40 years old and have as much as 90,000 hours and/or 70,000 cycles on them. I'm flying PIT/ATL Thursday night on a DC9-50. That plane is probably 35 or more years old.

The DC-9's Design Life Goal is 100,000 cycles, at 70,000 cycles it has lots of life left.
 
atlengineer
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 1:23 am

Quoting 474218 (Reply 8):
Quoting atlengineer (Reply 7):
If I remember correctly from Widgetheads, some of the Delta DC9-30's and 40's still flying are over 40 years old and have as much as 90,000 hours and/or 70,000 cycles on them. I'm flying PIT/ATL Thursday night on a DC9-50. That plane is probably 35 or more years old.

The DC-9's Design Life Goal is 100,000 cycles, at 70,000 cycles it has lots of life left.

Thanks 474218. Do you know what the Design Life Goal is for the MD88's and MD90's?

Barry
 
474218
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 2:13 am

Quoting atlengineer (Reply 9):
Thanks 474218. Do you know what the Design Life Goal is for the MD88's and MD90's?



MD-80 = 50,000
MD-90 = 60,000
 
EMBQA
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 4:36 am

Quoting flyby519 (Reply 4):
An idea what the "design life goal" for the ERJ 135/140/145 series is?

Again there really is none. Continue to maintain them and take care of them and you can keep flying them. Take poor care of them and you cut the life from them.
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cobra27
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 6:51 am

But what about corosion? Aluminium has a limited lifespan, tensile strength gradually reduces, unlike steel?
 
MQTmxguy
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 7:38 am

Quoting flyby519 (Reply 4):
An idea what the "design life goal" for the ERJ 135/140/145 series is? There are some older ones getting up over 30k cycles

I recall reading in the EMB-145 AMM part 1 that the airframe is designed for 60,000 cycles.
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macsog6
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 9:48 pm

Quoting JBo (Reply 2):
believe the DC-9 will be the only airworthy aircraft after the apocalypse

Sorry, DC-9's will be hauled to the scrap yards in DC-3's and C-130's.....

But more on point, the A380 is likely to first go to the parkling lot not as a result of cycles but as a result of a severe economic downturn making them - and other aircraft - surplus to demand. Now if I could only predict when that would happen.....
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PlymSpotter
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 10:02 pm

Quoting Macsog6 (Reply 14):
But more on point, the A380 is likely to first go to the parkling lot not as a result of cycles but as a result of a severe economic downturn making them - and other aircraft - surplus to demand. Now if I could only predict when that would happen.....

Actually it would be the opposite, unless the planet encounters a massive reduction in population. Anyway, aircraft are stored, not scrapped. We've just come through a severe economic downturn and many of those stored aircraft are being reactivated now - but note there is not a single A388 or 77W in storage. That's not just because they are new, that's because on average they are the most economic aircraft to keep flying compared to 744s and 343s, especially during a recession. In the A380s case, the only conceivable aircraft which is going to replace it is the A389.
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etherealsky
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 10:36 pm

Quoting EMBQA (Reply 1):
Aircraft do not have a limited life as long as you continue to maintain them

I believe this about unpressurized aircraft, but even pressurized ones? Aren't there critical, irreplaceable components that are eventually done-in by fatigue?

Quoting cobra27 (Reply 12):
But what about corosion? Aluminium has a limited lifespan, tensile strength gradually reduces, unlike steel?

Repairs can go a long way (my understanding is that the old Douglas, Lockheed, and McD products - and even Boeing to some extent - were so rugged that all you needed was to metaphorically "throw a patch on" and go fly. Maybe someone who worked on those beasts (DC-8, DC-10, 707, 727, etc.) can confirm that or not  
.

Quoting PlymSpotter (Reply 15):
Anyway, aircraft are stored, not scrapped.


This was the sight at KARG a couple months ago; all of those aircraft (and a few more out-of-frame) were in the process of being scrapped. The two ex-CO 737's in the top-right of the photo even had winglets.

Besides, there are always the lucky few that get turned into restaurants or hotels  
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 10:52 pm

Quoting etherealsky (Reply 16):
This was the sight at KARG a couple months ago; all of those aircraft (and a few more out-of-frame) were in the process of being scrapped.

The point of Plymspotter is that relative new aircraft will just be stored. Like some 744Fs were stored during the heavy cargo downturn last year but are now reactivated though. On your picture there are only aicraft built before about 1992.
While older aircraft, including MD-80s, 737-300/400/500 (the Continentals were old yet had winglets which probably were salvaged and put on other aircraft) some early A-320s, have been withdrawn to be scrapped, this happens more in a downturn but the current economic boom is not strong enough to save all older 1980s generation aircraft as enough new aircraft come on the market.
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474218
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RE: Limited Life Time Of Aircraft

Wed Aug 04, 2010 11:47 pm

Quoting etherealsky (Reply 16):
I believe this about unpressurized aircraft, but even pressurized ones? Aren't there critical, irreplaceable components that are eventually done-in by fatigue?


There are no "irreplaceable parts".
 
macsog6
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 1:45 am

Quoting Macsog6 (Reply 14):
first go to the parkling lot

I did not mention them being scrapped, I said parking lot.

Quoting PlymSpotter (Reply 15):
aircraft are stored, not scrapped

I agree.

I think you are assuming I said they would be scrapped and all I was saying was that economic conditions would likely cause them to be parked before they would ever be ready to be made into billions of beer cans.
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PlymSpotter
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 9:32 am

Quoting MEA-707 (Reply 17):
The point of Plymspotter is that relative new aircraft will just be stored. Like some 744Fs were stored during the heavy cargo downturn last year but are now reactivated though. On your picture there are only aicraft built before about 1992. While older aircraft, including MD-80s, 737-300/400/500 (the Continentals were old yet had winglets which probably were salvaged and put on other aircraft) some early A-320s, have been withdrawn to be scrapped, this happens more in a downturn but the current economic boom is not strong enough to save all older 1980s generation aircraft as enough new aircraft come on the market.

   Just what I was meaning; new fuel efficient aircraft are not going to be scrapped (yet) - unless they have a serious issue.

Quoting Macsog6 (Reply 19):

I agree.

I think you are assuming I said they would be scrapped and all I was saying was that economic conditions would likely cause them to be parked before they would ever be ready to be made into billions of beer cans.

Yes sorry, I wasn't aiming the bit about scrapping at you, just a general point.


Dan  
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Burkhard
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 9:36 am

Quoting PlymSpotter (Reply 20):
Just what I was meaning; new fuel efficient aircraft are not going to be scrapped (yet) - unless they have a serious issue.

In this case they may be more worth as spare parts than as a total, which is mostly the reason for young scrapped ones.
 
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 10:01 am

Quoting Burkhard (Reply 21):
In this case they may be more worth as spare parts than as a total, which is mostly the reason for young scrapped ones.

The Iberia A320 at BIO comes to mind here. Aircraft less than a year old but more economical to scrap than to repair.


Dan  
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SEPilot
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 4:18 pm

Quoting cobra27 (Reply 12):
But what about corosion? Aluminium has a limited lifespan, tensile strength gradually reduces, unlike steel?

Corrosion and fatigue are different issues, and corrosion affects both aluminum and steel. Fatigue, however, is what limits aircraft life. Steel, if stressed below a certain point, does not fatigue but has essentially infinite life. Aluminum does not. However, under low stress aluminum can work harden, which makes it stronger. This was discovered when Douglas got worried after WWII about all of the ex-military C-47's being put into civilian service, many with unknown history. They got one that had had a lot of wartime service and subjected it to the same stress tests as they had the original prototype. They were very much surprised to find that the wing failed at about 50% HIGHER load than the original; they ultimately attributed it to work hardening. Again, this is distinct from fatigue, which will still affect it. The main issue for airliners is fatigue from pressurization/depressurization; non-pressurized aircraft are generally not significantly affected by fatigue, with one notable exception: small aircraft used for pipeline inspections have had their wings fail from fatigue due to continual flying at low level in turbulent conditions. This happened to at least one Piper Cherokee, which resulted in an AD requiring removal and inspection of the wings after 5000 hours; this severely impacted the value of Cherokees while it was in force. After several years of inspections and not finding any problems, it was modified to only apply to aircraft subject to severe service, IIRC.
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 4:43 pm

Quoting etherealsky (Reply 16):
This was the sight at KARG a couple months ago; all of those aircraft (and a few more out-of-frame) were in the process of being scrapped. The two ex-CO 737's in the top-right of the photo even had winglets.



KARG is a scrapping facility, not for long term storage. The climate in Arkansas is much too humid, hence the reason most 'boneyards' are in desert locations.
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alwaysontherun
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 6:54 pm

I believe with GA aircraft it is much more simple.
No "cycles" as such………

As long as your engine is up to scratch and the airframe is looked after, I guess it can go "forever", right??
Without spending a fortune, that is.
Yes, you´d have your propeller, cables and instruments to replace at some stage, but as long as the airframe itself withstands the forces, it´s off you go go.

Quoting CanadianNorth (Reply 5):
apples to rear differentials comparison

Who´s "rear" are you comparing an apple with?

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413X3
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 7:21 pm

Quoting readytotaxi (Thread starter):
As all aircraft have a limited life

Really? DC-3's are still flying.
 
CanadianNorth
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RE: Limited Life Time Of Aircraft

Thu Aug 05, 2010 9:39 pm

Quoting alwaysontherun (Reply 25):
Who´s "rear" are you comparing an apple with?

Anyones really, I was just trying to say the 737's life has nothing to do really with the Embraer's, I was just throwing the fact out there.
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CanadianNorth  
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tdscanuck
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RE: Limited Life Time Of Aircraft

Tue Aug 10, 2010 8:15 am

Quoting EMBQA (Reply 1):
Aircraft do not have a limited life as long as you continue to maintain them.

This depends, almost entirely, on how the structural design was done. Anything that was designed as damage tolerant (which is every large jet in current production that I'm aware of) has a limited life.

Quoting JBo (Reply 2):
However, it is noted that some aircraft were designed and built to withstand a certain number of cycles, beyond which the performance/reliability is not guaranteed.

They're all targeted at some number of cycles (the design life)...depending on which structural concept was used in doing the fatigue work, that may translate into just a target, or an actual limit.

Quoting flyby519 (Reply 4):
An idea what the "design life goal" for the ERJ 135/140/145 series is? There are some older ones getting up over 30k cycles.

RJ's are often have design lives around 75-100k cycles.

Quoting CanadianNorth (Reply 5):
Life limit of most aircraft is, as said, basically the point at which it becomes more expensive to keep it airworthy than it would be to replace it.

No. That's an economic limit. Life limit is when the number of cycles exceeds the number of cycles the primary structure can reliably withstand (all aluminum airliners have finite life limits, it's just that for some of them the number of cycles is so long as to be functionally infinite).

Quoting EMBQA (Reply 11):
Quoting flyby519 (Reply 4):
An idea what the "design life goal" for the ERJ 135/140/145 series is?

Again there really is none.

There had to be...that's the only way they could have done the fatigue calculations, and the ERJ 135/140/145 are too new to have been designed without fatigue calculations.

Quoting cobra27 (Reply 12):
But what about corosion? Aluminium has a limited lifespan, tensile strength gradually reduces, unlike steel?

Proper maintenance can put off corrosion indefinitely, for all intents and purposes. But you can't maintain your way out of fatigue damage.

Quoting etherealsky (Reply 16):
Repairs can go a long way (my understanding is that the old Douglas, Lockheed, and McD products - and even Boeing to some extent - were so rugged that all you needed was to metaphorically "throw a patch on" and go fly.

Old airliners were safe life or fail safe, and done with hyper conservative stress calculations...this is the biggest reason for the "they don't make 'em like they used to" sentiment. They literally do not make them like they used to. Everything today is damage tolerant, which doesn't last as long but is considerably safer when within its design life.

Quoting 413X3 (Reply 26):
Quoting readytotaxi (Thread starter):
As all aircraft have a limited life

Really? DC-3's are still flying.

DC-3's were safe life. Very different than today.

Safe life: Each part has a target life (cycles) based on the material, design, and stress state. You must replace each part before it runs out its safe life. In days of yore, whole aircraft were done this way. Today, the only things left are those that are too highly stressed to be done any other way (engine disks, landing gear struts, etc.).

Safe life gave way to fail-safe, which is lighter and generally performs better. The idea here was that you have redundant load paths so that the failure of a part will not jeopardize the entire aircraft and you can safely get home. Unfortunately, it's really hard to do fail-safe right and prove that you go it right (e.g. the Dan Air 707 crash). There are also times when you really can't do it and you need a better way to deal with it (F-111 crashes). That brought us to...

Damage tolerant: damage tolerance assumes that you inspect the structure and that you have damage present, but it's smaller than your inspection process can detect. You figure out how long the structure can go until that undetected damage grows to be large enough to cause catastrophic failure. Then you inspect at some fraction of that time (often 1/3, 1/2, or 2/3). Inspecting "re-baselines" you so that you know the maximum size of damage you have once again, and you can start over. A consequence of this philosophy is that you *expect* to find fatigue damage during certain inspections, but you also expect it to be small enough that it's not threatening and you can repair it.

All current airliners I'm aware of are damage tolerance, so design cycle lives are an inherent part of their design philosophy.

Tom.
 
474218
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RE: Limited Life Time Of Aircraft

Tue Aug 10, 2010 12:52 pm

Quoting tdscanuck (Reply 28):
Quoting EMBQA (Reply 1):
Aircraft do not have a limited life as long as you continue to maintain them.

This depends, almost entirely, on how the structural design was done. Anything that was designed as damage tolerant (which is every large jet in current production that I'm aware of) has a limited life.

When Lockheed designed the L-1011 it was assumed that there was no maximum number of cycles/hours it could be operated as long as it was properly maintained. However, after the Aloha incident and the establishment of the FAA mandated Aging Aircraft Task Force it was determined that all commercial aircraft with a MTOW of 75,000 pounds or more would have a "design life goal".

Lockheed took a very conservative method when establishing the L-1011's "design life". They took the number of cycles the fatigue airframe was put through 72,000 and divided it in half and came up with a "design life goal" of 36,000 cycles. I am not sure if this same procedure was used by the the manfactures?
 
soon7x7
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RE: Limited Life Time Of Aircraft

Wed Aug 11, 2010 1:07 pm

Quoting 413X3 (Reply 26):
Really? DC-3's are still flying.

The last DC3 revenue flight I was on was at the time, the only commercial aircraft with 146,000 hours on her. She belonged to PBA airlines I'll bet she still flies. AerLingus flew EI-BED (747-100) to 101,000 hours. She was designed for roughly 65,000 hours. Originally a Lufthansa ship, she ended up with several other carriers before ending up back with AerLingus.
 
j0rdan
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RE: Limited Life Time Of Aircraft

Fri Aug 13, 2010 8:34 am

Quoting PlymSpotter (Reply 15):
but note there is not a single A388 or 77W in storage.

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soon7x7
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RE: Limited Life Time Of Aircraft

Sat Aug 14, 2010 2:49 pm

Now A busers...don't get mad...I'm not trying to start an A/B war but it is a fair question I'm going to ask. I have been seeing a fair amount of A320, A340's already being parted out and cut up. These airframes are only about 10-15 years old. While many MD's and Boeings serve an easy 25-30 years. What is the intended life span put forth by Airbus on their airframes?. A buddy of mine that flies both types considers Airbuses to be "disposable airframes". Personally, I really like Airbus products but their early retirement is of interest to me. I've been helping some people dispose of an A300. That aircraft specifically to me is built everbit as well as anything else I have chopped into. It did have the conventional alloy tail feathers though, not the CFRP's. Any "Kind" responses?

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