Some problems for A380...

JVJASON · Post by **JVJASON** » 18 Feb 2006, 11:03

Hello everybody,

Heard yesterday on French radio :

Some days ago, engineers and technicians performing resistance tests on an A380 airframe in Toulouse had a very bad surprise when they heard a cracking sound coming from the wings. They where simulating the conditions of a hard landing at full load or flying with strong turbulence by applying hydraulic jacks on the airframe and beneath the wings. Suddenly both wings cracked approx. on the same place (between inner and outer engine). The airframe has to undergo deep examination and planes in production wil probably receive structural reinforcements before tests could go further. This may cause a new delay in delivery of the first aircrafts, and for commercial exploitation to be allowed.

According to the engineers the cracks happened "at 3% before the expected resistance limit"; at that moment the wingtips had already been moved 7,4 meters upwards from initial position.

blackhawk · Post by **blackhawk** » 18 Feb 2006, 11:06

topic in dutch for more information: https://www.aviation24.be/postt15506.html

LX-LGX · Post by **LX-LGX** » 18 Feb 2006, 12:55

don't panic: it was not what the press is saying.

It was a planned test to find out what the maximum pressure on the wings now really is. The wings indeed cracked at a pressure, some 4% lower then what the computer had calculated. But even at that 4% margin, there is no security problem.

the break point will never be reached, even not in the worst scenario a flight engineer can imagine.

DFW · Post by **DFW** » 18 Feb 2006, 21:04

Here's the article in Flight International:
http://www.flightglobal.com/Articles/20 ... +load.html

It is a setback, meaning Airbus will now have to work to resolve it and allay customer worries. But I don't think it should be that worrisome. As the article states, they were within 3% of the target ultimate load. And they can probably isolate the failure down to one component and redesign it.

And its not static load failures that keep engineers up at night; it's fatigue failures.

bits44 · Post by **bits44** » 20 Feb 2006, 03:50

This is a picture of the Boeing 777 wing static load test, it passed by the way at 154%

http://www.bjones4.dsl.pipex.com/777wing2.jpg

Ovostar · Post by **Ovostar** » 20 Feb 2006, 13:19

scary!

an-148 · Post by **an-148** » 20 Feb 2006, 13:46

@ bits44
at 154% of the calculated value?
then, it's time to buy new software

bits44 · Post by **bits44** » 20 Feb 2006, 13:58

at 154% of the calculated value?

Sorry that should have been 1.54 times

This iilustrates the amount of flex endured during the test, so when one encounters a little turbulance, and you are looking out the window, and the wing tip flex's a foot or two! be comforted that is very normal.

tolipanebas · Post by **tolipanebas** » 20 Feb 2006, 14:00

Indeed, Boeing was off by 4%!
It was lucky to be on the good side this time, but their calculations were not really correct....
Themargin of error is expressed in absolute value, so the result of the test on the 777 was off by even more than on the A380, not something to be really proud of, unless you focus on the 'accidental overperformance' and spin it that way, (which is what Boeing did)

an-148 · Post by **an-148** » 20 Feb 2006, 14:04

btw, 154% and 1.54 times is like "green cabbage" and "cabbage, the green one"

Avro · Post by **Avro** » 20 Feb 2006, 15:16

AFAIK 100% means the worst one could ever encounter during a flight.

Chris

fleabyte · Post by **fleabyte** » 21 Feb 2006, 00:19

the A380 is sounding kinda scary

RC20 · Post by **RC20** » 21 Feb 2006, 03:39

tolipanebas wrote:Indeed, Boeing was off by 4%!
It was lucky to be on the good side this time, but their calculations were not really correct....
Themargin of error is expressed in absolute value, so the result of the test on the 777 was off by even more than on the A380, not something to be really proud of, unless you focus on the 'accidental overperformance' and spin it that way, (which is what Boeing did)

Boeing is noted for their conservative design. Airbus is not. Which would you rather be flying in?

Amazing to think that you accuse Boeing of spinning a positive aspect.

Lets see now, the A380 was grossly overweight, and they had to spend 1.3 Billion Euros to lighten up, the engine did not meet noise limits and they had to redesign, they are 6 to 8 month behind (and accusing the owners of causing that problem), and now I read they are using alumunium wire in it (more of that weight saving issue). Where else did they cut corners?

That stuff is bad enough where you have good access to work on it.

It will be an interesting ride, and I am glad where I fly, its Boeing with their terrible record of building overly reliable aircraft.

DFW · Post by **DFW** » 21 Feb 2006, 23:07

What's this all about?
http://www.flightglobal.com/Articles/20 ... early.html

Is the 1.5 FS a requirement or not? When did "close enough" satisfy a requirement? I'm well aware that 1.5 loads would theoretically never be achieved, but that's not the point. The point is that if a requirement is defined, then it needs to be adhered to. When did certifications become negotiable? :frusty:

bits44 · Post by **bits44** » 22 Feb 2006, 00:21

You'll note that it stated EASA not FAA, who I believe will require a further test to failure that meets the standard of 1.5.

Its like being a little bit pregnant, you either are or you aren't

close only counts in Atom bombs and hand grenades.

Avro · Post by **Avro** » 22 Feb 2006, 13:36

fleabyte wrote:the A380 is sounding kinda scary

Thanks for the constructive message. Do you think it's scary just because they are now off by 4% during testing ? That's what the testing is about. Look at the result and compare them to your numerical predictions. If you don't meet the requirements just fix the problem. It's as simple as that and it doesn't make the plane less safe.

Boeing is noted for their conservative design. Airbus is not. Which would you rather be flying in?

Indeed Boeing is known for its conservative predictions. But Tolipanebas was right in a way as well. The Finite element code of Boeing also produced a similar error but here on the more conservative side.

As already stated Airbus will have to do adjustments to meet the requirements. Now which plane I'd rather fly ? I don't care!! In the end both planes meet the requirements. And to be honest I don't care if I fly a plane where the wing brakes of at 150% of the max load which could be encountered once or at 154% . The probability of being in a situation where you encounter nearly 150% is already nearly zero.

Chris

Ruscoe · Post by **Ruscoe** » 22 Feb 2006, 14:22

The point is I think that the 777 did not fail before the certification threshold. Engineers at A&B know there is a certain level of uncertainty.
Airbus engineers should have set up a higher margin to cover error. I wonder how much of this is due to over zealous weight reduction programs.
Ruscoe

DFW · Post by **DFW** » 22 Feb 2006, 16:12

Upon reading the Flight International article again, maybe I overreacted...but only a little bit.

Airbus is quoted as saying the production wing is different from the test wing, owing to modifications needed to accommodate higher airplane weight. Their position is that they can show EASA sufficient FEM analysis that the production design meet the 1.5 FS.

I'm okay with that approach as long as the certifying body takes a conservative stance on the analysis. I didn't care for the implication that "close enough" would meet the requirement.

Anyways, I'm not picking on EASA. In years past, the FAA has been known to be in bed with Boeing. Critics were saying that a certifying body that also has the mandate to promote aviation has a clear conflict of interest. That was suppose to have changed a few years ago.

biker_thai · Post by **biker_thai** » 22 Feb 2006, 16:33

FYI - Airplanes wings are designed to Limit load. Limit load is the highest load the airplane will ever anticipated to see. I.E. Pulling out of a really, leally steep dive. How steep a dive? Well, the FAA defines the G loading in FAR Part 25. The wings are then design to 1.5 times limit (Called Ultimate). So they take the worst case situation and add 50% margin. This is required by FAA. Same regulation.

Now as for the A380 wing test. True the 3% failure before ultimate will not affect A380 delivery. However, Airbus will face some challenges.

1) Analysis will only go so far. There are so many assumptions in analysis that test are usually done to verify analysis. So test results usually trumps analysis. They will take the results and refine the analysis.

2) The 3% short fall would mean that unless Airbus redesign some portions of the wing, any A380 aircraft flying with configuration as tested will have to fly a 3% below max gross weight . The airplane can still fly. It just have to fly with less cargo.

3) Boeing is conservative with their design. The 1.54 margin (4% above Ultimate) test value for the 777 allow the Engineer to go back and added growth capabilities with out additional redesign.

One have to look at the A380 wing test from a value stand point. How much money will it cost to re-design the wing to meet the 3% margin, or how much revenue will the A380 loses because it has to fly with 3% less max gross weight.

chornedsnorkack · Post by **chornedsnorkack** » 22 Feb 2006, 16:50

So, how much would it cost for Airbus to build a new production wing and break it, and show that the production wing breaks at 154% or 150,5% or anything over 150% the design load?

And how much time would it take, assuming they have not planned on the extra production wing to break?

Aviation24.be

Some problems for A380...

Some problems for A380...

I will ride the planer that errs on conservative side

Re: I will ride the planer that errs on conservative side

Test wing