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New problems with A300 rudders

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New problems with A300 rudders

Old 24th Mar 2006, 22:36
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New problems with A300 rudders

Hello all.

Before we start bashing each other as A. or B. proponents please read this carefully.
We all can not imagine what will happen with new composite structures used on A330/340, B777 and newer products (B787, A350) after 25 years.

Fatigue in composite structures is still an open issue, both in research field and in application.
In light of that, hopefully, NTSB's requirement and probably further Airbus investigative work would help.

******************************

24 MAR 2006 NTSB urges inspections of certain Airbus A.300 rudders
The NTSB urged the FAA to order inspections of the inner skin of the composite rudder surfaces of certain Airbus A-300 series airplanes. The safety recommendations (one of which is classified as urgent) address a safety issue identified during the investigation of damage found during an inspection of a rudder from a Federal Express A.300-600 airplane. The Board noted that this incident might have applicability to a more serious rudder separation that occurred last year when an Air Transat A.310 suffered an almost complete rudder separation. (NTSB)
http://www.ntsb.gov/recs/letters/2006/A06_27_28.pdf

Last edited by Grunf; 25th Mar 2006 at 01:03.
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Old 25th Mar 2006, 01:25
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Hell, that's a nasty one!
And it is not only the A300 which has plastic in the tail (and elsewhere).
Hate to think about it, but there may be some gruesome times ahead...

Ikarus
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Old 25th Mar 2006, 04:14
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Ah, yes.......
And the high tech "tap test"......
When new materials are developed, in concert should be ways to test them. This is not the first, nor will it be the last, of recomendations/A.D.'s on composites used in primary stucture.
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Old 25th Mar 2006, 08:38
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In the modern version of Pandora's Box, "advanced technology" is one of the trickier devils. The benefits of faster, lighter, cheaper, longer service life, etc. are tempting bait for justification of new methods and materials. Every effort is, or should be, made to ensure proper engineering and testing of the new technology, and then it goes out into the world to confront the realities of long, hard use in astonishingly difficult conditions with little tolerance for weakness and great penalties for failure.

Some technologies - such as those in engine structures and components - have maintenance intervals and teardown cycles that reveal incipient faults. Others, including primary structures and materials embedded deep within the airframe, are not amenable to casual review. Some of us speculate that the technology for evaluating the strength and margin of safety for composite materials in air carrier applications may not have caught up with the rapidly expanding use of these materials.

A similar disconnect between design element complexity and limited availability of effective means for maintenance seems likely also to become manifest in the hardware, software, and the wiring of systems for flight controls, engines, and other automated functions. A hundred years from now, perhaps very detailed and thoroughly reviewed public standards will exist for fail-soft functionality and diagnosability of all critical subsystems. At present, the standards and methods at the finest levels of detail are mostly at the discretion of the manufacturing companies, who are unlikely to freely disclose critical data about flaws when company-killing problems and litigation arise.

There will be interesting times to come, as the 21st century airframe fleet ages. A new generation of scary problems may necessitate aggressively raising the bar for maintainability methods and standards.
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Old 25th Mar 2006, 09:44
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Arcniz

Good post

It seems to me that what is happening in regard to composites being used for primary structure is that the very long final stage of development and testing is being done in service. I have no problem with that as a concept myself, even though I have no doubt that some people will die as a result. I say this because the only completely risk free way to tackle such advances is not to make them.

Whether we talk of people dying because of B737 rudder actuation or A300 rudder control forces and displacements I believe the certification authorities have got it very right when it comes to their practical approach in analysing the risks and benefits of not taking stronger retrospective modification action.

If you need to travel a long way in a short time a passenger ticket to fly somewhere is a remarkably cheap purchase that allows a very productive use of half a day. However uncomfortable, unpleasant and boring the experience may be there is no justification for suggesting it is a dangerous way to meet your objective.
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Old 25th Mar 2006, 11:15
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NTSB Orders A300 fin inspections

Is it possible to post this without being cited for anti -Airbus syndrome?
25th March 2006:NTSB cites inspections -on A300 fins- 1 being an urgent.
Got to:
http://www.ntsb.gov/letters/2006/AO6_27_28.pdf

So, away from the hype and the mass media rubbish, do we now have formal recognition of an ageing composites issue?

What of the manufacturing issues?

One thing may now be obvious, bunging the same fin design on a range of fuselages, power plants etc, with consequent effects on thrust lines, centres of pressure, polar inertia and lever arm fulcrum, never mind airflow patterns and G breaks, may be pushing the plastic too far...
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Old 25th Mar 2006, 13:28
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I don't understand how these "honeycomb core and fibreglass composite skin" structures can really be considered so advanced and untested ...they've been used in boat building for donkey's years now and not a single yacht I know of has ever fallen out of the sky yet!

Uhmmm well, there have been a few embarassing occasions when an America's cup boat or two might have lost its keel and everyone became inverted I suppose.
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Old 25th Mar 2006, 13:50
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ASFKAP, I believe the B4 model uses an aluminum fin and rudder, but I stand to be corrected.

It seems to me that if a "tap" test (and listening to the sounds it makes) has a degree of effectness in determining if voids exist between the honeycomb inner core and outer skin of a composite structure, then this screams out to me that imaging ultra-sound methods could be the anwser for inspecting composite airframe structures.
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Old 25th Mar 2006, 15:06
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Delamination and blistering continue to beleaguer boat-builders well over 3 decades after composites became commonplace in the industry. And the "tap-test" is the most current form of looking for problems, provided the area is accessible to the surveyor...

This joint FAA/DoD/NASA on more modern methods of "NONDESTRUCTIVE INSPECTION OF COMPOSITES AND THEIR REPAIRS" might offer some insight.

Looks like FS' ultrasound technique is the way forward...

In 2012, an Air France engineer using ultrasound is inspecting a suspicious bubble in the underbelly of an A-380:

"Mon Dieu! Jacques, come and have a look at zis..."
"Sacré bleu! Eees eet what I think eet looks like?"
"Oui Jacques, she ees with child! A-320s? Twins no less!"
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Old 25th Mar 2006, 21:01
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Airship:
Sadly I do not see much development in that direction. Fatigue analysis is (for metals) well covered in academia. However it is still a sort of a problem in aerospace no matter how long the topic is present.
Nobody can still claim it found "the" method for crack detection, propagation etc.
Same holds for different types of composites. In my opinion, largest problem would be that different OEMs have different approach to composites in terms of application, manufacturing and after EIS keeping it functional.
It seems that every new type introduced brings new suggested repairs and inspections. It was easier with metal due to its crystal structure which was easier to predict. Still metal fatigue do present a problem, at least in aerospace.
the whole point I would like to address is that we are just getting into an era with far more composite primary structure vehicles and we can see more incidents like this simply because it is the first time we use composites in such way.
A300 is a good example because it is more or less one of the first commercial programs with composites in the structure.
Let us wait and see what will come out of more advanced programs that came out latter.

In my opinion, the only way to be sure of the flaw is to have 10exp-9 size gauges embedded all over the structure and constantly monitored. We are years away from that.
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Old 25th Mar 2006, 22:16
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Airship, a composite yacht doesn't go from 0 to 450+ knots about six times a day, suffers a temperature change from +30 to -56c every time it flies,gets vibrated,twisted ,bent and subject to 1+g manoeuvres also a couple of times a day.
Shortly after the A330-200 was introduced Airbus had an Ad that required a large rivet job to the fin.If you are really bored and you can see them count how many rivets there are in a 330 fin.Don't forget to count both sides!I think it was around 1000+
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Old 26th Mar 2006, 03:17
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Originally Posted by airship
I don't understand how these "honeycomb core and fibreglass composite skin" structures can really be considered so advanced and untested ...they've been used in boat building for donkey's years now and not a single yacht I know of has ever fallen out of the sky yet!
Uhmmm well, there have been a few embarassing occasions when an America's cup boat or two might have lost its keel and everyone became inverted I suppose.
Of course the yachts don't use skydrol in their hydraulic systems either. Skydrol is great stuff in its place but it appears that it's place is not in the A300 tail structure.
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Old 26th Mar 2006, 19:23
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n5296s,how do i know this? I have been flying the airbusfamily for 14 years and the physics and atmosphere have not changed!!!!
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Old 27th Mar 2006, 06:26
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Many years ago when metal analysis programs were still developing, we did heavy checks on aircraft that went down to the last nut and bolt.
As metalurgy developed we were able to ascertain were the critical areas were and developed electronic tequniques to inspect these areas in high definition electronically. The result was that the heavy checks were greatly reduced without impairing safety.
It seems to me that the composte aircraft has slotted into the metal aircraft maintenance program without the real handle on the long term analysis and effects.

I visited Dornier factory at Oberthingy when they were just starting the Sea star program and they told me that developing the aircraft was not the problem - developing the maintence and structural inspections were the real challange
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Old 27th Mar 2006, 06:47
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Having done a bit of gliding, I'm aware that composite airframe life has become an issue as some glass gliders are over 30 years old. I believe a lot of research has been done on this, particularly by German manufacturers. Maybe a possibility to exchange information?
No bits have fallen off my (steel!) yacht lately, but then Vne is 8 knots....
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Old 28th Mar 2006, 09:37
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Manufacturers always test 1 airframe to failure during certification, but I wonder what would the results be if they tested a similar one 30 years later.

Would be very interesting if manufactureres would test say a 747-200 and A300 both over 25 years old and see how they stand up compared to how the new airframes did when they were certified
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Old 28th Mar 2006, 09:51
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Is the vertical stab also composite on this aircraft, or is that piece aluminium? Outside of the comment about rudder failure causing a period of high loading on the fin, there isn't alot of information about this, other than a suggestion that "....high stresses may have been dangerously close in magnitude to those that caused the in-flight separation of the vertical stabiliser....involving American Airlines flight 587."

This must be an interesting area of research.

Last edited by JamesT73J; 28th Mar 2006 at 09:55. Reason: clarity
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Old 28th Mar 2006, 10:32
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Originally Posted by cornwallis
Airship, a composite yacht doesn't go from 0 to 450+ knots about six times a day, suffers a temperature change from +30 to -56c every time it flies,gets vibrated,twisted ,bent and subject to 1+g manoeuvres also a couple of times a day.
Yachts get a severe pounding and they do indeed break up....

http://www.thelognewspaper.com/news/...w.asp?c=179603

http://news.bbc.co.uk/sport1/hi/othe...ng/4206497.stm

http://www.sailingbreezes.com/sailin...3/disaster.htm
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Old 28th Mar 2006, 10:49
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Helicopters have been flying with composite blades for about 15 years now. The stresses/ 'cycles' on these must be astronomical when compared to F/Wing aircraft so they must offer a rich source of data. Has anyone done the research?
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Old 28th Mar 2006, 13:55
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fokker

What you say is true. However heli blades do not suffer the pressure/humidity/temperature cycles in the same way as airliners which can all affect moisture uptake. On Concorde for example there was a huge fatigue rig needed to represent the kinetic heating cycles as well as the loads.
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