b767
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A320 Series Structural Strenght?

Wed Feb 18, 2009 2:01 am

In several disqussions on A.net about Boeing versus Airbus,many claim the 737 for being much tougher built than the Airbus A320.Is this realy correct?In the recent Hudson incident,the bus looked remarkedly well after hitting the river.I also remember a Iberia windshear incident where the A320 hit the runway at 1200 or 1400 ft/min.The nose gear collapsed, but the main gear did not,nor did the body.So I would like to hear the opinion from someone in the industrie with knowledge.
 
474218
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 4:34 am

The A320 series aircraft have a design life goal of 48,000 cycles. As a comparison the B737 series aircraft design life goal is 75,000 cycles.
 
tdscanuck
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 5:57 am



Quoting B767 (Thread starter):
In several disqussions on A.net about Boeing versus Airbus,many claim the 737 for being much tougher built than the Airbus A320.Is this realy correct?

It depends on what you mean by "tougher." As 474218 correctly pointed out, the two designs have different design life targets, which has implications for the durability of the airframe over long periods, but it will only show up on parts that are fatigue critical to start with.

If you just mean static strength, then they're designed to the same FAR's and, given how close they are in performance, I suspect they've both got about the same safety margins so they should be very comparable in that regard.

Tom.
 
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zeke
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 8:02 am



Quoting 474218 (Reply 1):
The A320 series aircraft have a design life goal of 48,000 cycles. As a comparison the B737 series aircraft design life goal is 75,000 cycles.

I seem to recall from the Aloha accident that the original life was 20,000 hrs on the 737, was that extended after EIS ?

The A320 is currently getting an extended service goal of 90,000 flight cycles and 180,000 flight hours.
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wing
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 8:59 am

The number of design cycles is not related with the structural strength of the airplane.Even if it is designed to fly 100 times or 100000 times it should withstand the same forces that it will encounter in the air..

My opinion as I flew both the 737 and A320,I say they don't have a difference of structural strength that you can feel.I have been in weather situations that both airframes proved to be very Strong.On a side note I found that A320 autopilot goes off much harder than the 737 autopilot in very turbulent conditions.
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Starlionblue
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 11:48 am



Quoting Zeke (Reply 3):
I seem to recall from the Aloha accident that the original life was 20,000 hrs on the 737, was that extended after EIS ?

Wasn't that a 737 Jurassic? I assume the 75k figure is for a 737NG.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
LY744
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 4:29 pm



Quoting 474218 (Reply 1):
As a comparison the B737 series aircraft design life goal is 75,000 cycles.

By the way, is there an absolute flight hour limit for the 737? I seem to recall some Airbus products (A310, maybe A320) were to have a life of 80,000hrs, but I've never encountered a similar statistic for a Boeing.


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747400sp
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 4:51 pm

Seeing that the 737 was built off the 707 and 727 design, and also seeing that both of those a/c were was flying tanks with out guns, I would think the 737 would be stronger than an A320.
 
474218
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 10:15 pm



Quoting Zeke (Reply 3):
I seem to recall from the Aloha accident that the original life was 20,000 hrs on the 737, was that extended after EIS ?

After the Aloha incident the FAA established several task forces made up of Regulatory Agencies, the Airlines and the Manfactures to establish recommendations that would prevent another incident caused by "wide spread fatague damage". In the case of the Aloha 737 there were many small cracks when combined together causing the failure. Because these small cracks were missed during the scheduled maintenance, special inspections would now be required.

The design life goal is the point in the airframe life where the manufacture has determined that additional inspections and modifications (beyond the regular scheduled maintenance) required to keep their aircraft airworthy. Each manufacture has predetermined what maintenance is required when the design life is reached. The operator can incorporate these service bulletins, which will then establish a new design life goal. This can go on and on as long as the operator is willing to pay for the required modifications and the manufacture continues to supply the engineering data that proves the modifications will keep the airframe airworthy.

Airbus has chosen to establish rather low design life goals (48,000 cycles for the A320 series) which means fewer inspections/modifications may be necessary to establish this new goal. Boeing has gone a different direction (which surprises no one) and establishes their design life goal higher (75,000 cycles for the 737 series) which means more work may be required to establish a new goal. It the old adage "pay me now or pay me later" but if you want to fly an aircraft beyond its design life goal you have to pay.
 
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zeke
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 11:12 pm



Quoting Starlionblue (Reply 5):
Wasn't that a 737 Jurassic? I assume the 75k figure is for a 737NG.

They both share the same TCDS, and certification basis. Only major changes like the wing on the NG were certified to newer standards.

Quoting 474218 (Reply 8):

The Aloha accident was the second time that same sort of problem happened on a 737, a Far Eastern Air Transport (FEAT) 737 (ex UA) disintegrated midair for similar reasons after around 33,000 cycles about 7 years prior to the Aloha accident. All people died on the FEAT aircraft.

Boeing and the FAA had a lot of warning before Aloha (1988), they had the Dan Air Boeing 707 crash in 1977, and the FEAT 737 crash in 1981.

The A320 was 48,000 cycles or 60,000 hrs, the first A320 to reach 60,000 only did so in 2007, A320 from what I understand has come close to 48,000 cycles, indications are that the first A320 will reach 48,000 cycles next year 2010.

Airbus has done a great article on the A320 ESG for their customers to know what the plan is
http://www.airbus.com/store/mm_repos...st_41_a320_longer_service_life.pdf
We are addicted to our thoughts. We cannot change anything if we cannot change our thinking – Santosh Kalwar
 
EMBQA
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 11:21 pm

A friend sent me a series of nearly 200 photographs of the USAirways A320 and it took quite the beating. Much of the zone 100 area is destroyed and crushed. But I really don't think that has any bearing on life span... it did its job and everyone walked away
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474218
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RE: A320 Series Structural Strenght?

Wed Feb 18, 2009 11:56 pm



Quoting Zeke (Reply 9):
The Aloha accident was the second time that same sort of problem happened on a 737, a Far Eastern Air Transport (FEAT) 737 (ex UA) disintegrated midair for similar reasons after around 33,000 cycles about 7 years prior to the Aloha accident. All people died on the FEAT aircraft.

Two completely different problems: The FEAT accident was caused by corrosion/cracking in the fuselage lower lobe (belly skin). While the Aloha incident was caused by fatigue brought on by cold bond sealing of the lap joints in the fuselage upper lobe.

One of the inspections that came out of the Aloha incident was inspection of the lap joints on all commercial aircraft, even those that did not have cold bonded joints like Boeing used. A complete 100% ultrasonic inspection of all the lap joints on an aircraft like the L-1011 took several days and even required cutting access holes to get to some of the joints.
 
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RE: A320 Series Structural Strenght?

Thu Feb 19, 2009 1:27 am



Quoting 474218 (Reply 1):
As a comparison the B737 series aircraft design life goal is 75,000 cycles.

That's not quite the 737NG design life cycle goal.

Quoting Zeke (Reply 3):

I seem to recall from the Aloha accident that the original life was 20,000 hrs on the 737, was that extended after EIS ?

That's way off of the truth. 737 is designed for more cycles than that. Airplanes are usually designed on cycles and not hours. Cycles are a better reflection of how often components are used. Something like the landing gear, brakes, spoilers, doors, etc are based on number of flights as a longer flight does not increase demand or usage.

Quoting Wing (Reply 4):
.Even if it is designed to fly 100 times or 100000 times it should withstand the same forces that it will encounter in the air..

Yes and no. Airplane parts are subject to fatigue. You never design anything to a maximum load but rather a life cycle load. You cut a load by 10% and its lifetime will double. The length of service is important when designing components.
If you have never designed an airplane part before, let the real designers do the work!
 
tdscanuck
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RE: A320 Series Structural Strenght?

Thu Feb 19, 2009 1:32 am



Quoting Zeke (Reply 3):
I seem to recall from the Aloha accident that the original life was 20,000 hrs on the 737, was that extended after EIS ?

It's different for the 737-Jurassics, -Classics, and -NG's.

Quoting Wing (Reply 4):
The number of design cycles is not related with the structural strength of the airplane.Even if it is designed to fly 100 times or 100000 times it should withstand the same forces that it will encounter in the air..

They can be related. On a fatigue critical part, the stress the part withstands is driven by fatigue life, not the ultimate load. That may result in a part that can withstand far more force than any static loading case would require.

Quoting Zeke (Reply 9):
Quoting Starlionblue (Reply 5):
Wasn't that a 737 Jurassic? I assume the 75k figure is for a 737NG.

They both share the same TCDS, and certification basis.

True, but TCDS and certification basis have nothing to do with design life.

Quoting Zeke (Reply 9):
Boeing and the FAA had a lot of warning before Aloha (1988), they had the Dan Air Boeing 707 crash in 1977

Dan Air wasn't a multi-site damage failure. It's a totally different failure mechanism. Knowing about Dan Air wouldn't have helped prevent Aloha.

Tom.
 
474218
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RE: A320 Series Structural Strenght?

Thu Feb 19, 2009 1:54 am



Quoting RoseFlyer (Reply 12):
That's not quite the 737NG design life cycle goal.

According to the proposed NPRM on "Wide Spread Fatigue Damage" dated 18 April 2006 the Design Service Life Goal for the Boeing 737 is 75,000 cycles.
 
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zeke
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RE: A320 Series Structural Strenght?

Thu Feb 19, 2009 8:32 am

Quoting RoseFlyer (Reply 12):
That's way off of the truth. 737 is designed for more cycles than that. Airplanes are usually designed on cycles and not hours. Cycles are a better reflection of how often components are used. Something like the landing gear, brakes, spoilers, doors, etc are based on number of flights as a longer flight does not increase demand or usage.

from http://www.system-safety.com/PPT%20F...ines%20Flight%20243%20V2%20PPT.pdf

"Design service life of airplane (20,000 hours) was such that fatigue analysis of joint fasteners, or effects of corrosion did not need to be considered"

I should add, I think all pressurised aircraft are designed to a combination of hours and cycles to define a fatigue spectrum, short haul aircraft would have a lower flight hours to cycle ratio than a long haul aircraft.

[Edited 2009-02-19 00:45:07]
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