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Cracks found in A380 wing ribs

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Cracks found in A380 wing ribs

Old 20th Jan 2012, 17:09
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Anyone Else the Least Bit Concerned?

A380 wings to be checked for cracks, EASA says Airbus said there was no immediate threat to safety. (maybe later then)

Twenty Airbus A380s will have to undergo checks for cracks in their wings, the safety regulator has said.

The European Aviation Safety Agency (EASA) said the planes, a third of the current fleet, would undergo a "visual inspection" for cracks.

A few planes, which have carried out more than 1,800 flights, will need inspections within four days, it said.

Airbus said the cracks were not an immediate threat to safety. If cracks are found it will carry out repairs.

The problems could affect planes operated by Singapore Airlines, Emirates and Air France.

Cracks

The agency said it has determined that the cracks may develop on aeroplanes after a "period of time" in service.

"This condition, if not detected and corrected, could potentially affect the structural integrity of the aeroplane," said the agency in its directive ordering the inspections.

This is the second set of cracks found on A380 wings.

The first, which were less serious, emerged during repairs to a Qantas A380 following a blowout of its Rolls Royce engine in November 2010.

That prompted more widespread investigations and more serious cracks were found in the UK-made wings on Thursday.

If more, similar, cracks are found aircraft may be grounded in order to carry out a repair programme agreed between Airbus and regulators.

Repairs

Only planes which have carried out more than 1,800 flights are being targeted urgently, those which have flown between 1,300 and 1,800 flights must be tested within 6 weeks.

"Airbus confirms that during routine inspections some additional cracks have been found on a limited number of non-critical brackets (known as rib-skin attachments or wing rib feet) inside the wings of some A380s," the company said in a statement.

However EASA warned further steps may be needed.

"As a result of the on-going investigation, further mandatory action might be considered."

(manager tech ops, me)
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Old 20th Jan 2012, 23:06
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It's weird.

Brand new aircraft, top engineering and latest technology.

Cracks in the correct places that are expected is one thing, especially after years of service.

But this is different. Very different. Airbus didn't expect them, and their official statement makes me think they are as surprised as the engineers seeing them for the first time.

I am sure they will all be grounded until thorough checks and tests has been done, together with necessary repairs... And this will cost Airbus more money and reputation.

There is nothing like a reliable and safe Boeing.
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Old 20th Jan 2012, 23:31
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My understanding is that the cracking issue is an assembly problem, neither design nor fatigue related. No design changes required, but more careful attention to assembly processes to avoid pre-loading the structure.
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Old 20th Jan 2012, 23:53
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Cool

Hi,

So .. this is a minor problem ...

Further to this finding, inspections were carried out on a number of other
aeroplanes where further cracks have been found. During one of those
inspections, a new form of rib foot cracking originating from the forward and aft
edges of the vertical web of the rib feet has been identified (Type 2 cracks
according to Airbus AOT terminology). The new form of cracking is more
significant than the original rib foot hole cracking. It has been determined that
the Type 2 cracks may develop on other aeroplanes after a period of time in
service.

This condition, if not detected and corrected, could potentially affect the
structural integrity of the aeroplane.

For the reasons described above, this AD requires a Detailed Visual Inspection
(DVI) of certain wing rib feet. This AD also requires reporting the inspection
results to Airbus.
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Old 21st Jan 2012, 00:24
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Originally Posted by jcjeant View Post
Hi,

So .. this is a minor problem ...
My gut reaction is that it is less of a problem than turbine disks which like to go out and get some fresh air by way a high speed transit through the wing...
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Old 21st Jan 2012, 01:58
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Stop fretting, the boys are on it!
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Old 21st Jan 2012, 03:40
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Originally Posted by infrequentflyer789
My gut reaction is that it is less of a problem than turbine disks which like to go out and get some fresh air by way a high speed transit through the wing...
Well, let's be fair.

That engine came apart thanks to a failed oil seal.

But it's like they say: One structural failure can ruin your whole day (cracks or shrapnel? Who's counting?)

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Old 21st Jan 2012, 04:50
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hangar layover

so.. does this mean that my seat on the upper deck of an A380 on Tuesday out of CDG might not have me in it ?

Would you guys be calling the airlines asking for a change of intinerary ? Now im not so excited about the nice upgrade I got. I mean don't get me wrong.. I'm happy to go to Heaven, but not via hitting the ground ( or water) first!
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Old 21st Jan 2012, 04:53
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I've ridden the A380 (LH) and I would do so again.

The taxi ride to the airport is still the most dangerous part of the journey.



But still, we need to call a spade a spade.

Bon voyage.
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Old 21st Jan 2012, 14:05
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Sassy,

by that time, Tuesday, the most affected airplanes should not be flying anymore. Possibly, however, you might find yourself on some other airplane if too many of them are in the check and therefore not available.

Whether to rebook or not in the end you have to make that decision. I don't think any airline right now would blame you.

Novelty is always interesting but one has to remember that while the early bird might get the worm, only the second mouse gets the cheese!
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Old 21st Jan 2012, 14:35
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The European Aviation Safety Agency has issued a directive requiring precautionary checks on brackets within the wings of certain Airbus A380 aircraft. We are liaising closely with Airbus and are carrying out inspections in full compliance with the directive.


As checks are being carried out, some flights normally operated by A380s will be temporarily operated by other aircraft. We apologise for any inconvenience caused.


Affected flights at this stage will include SQ346 from Singapore to Zurich and SQ345 from Zurich to Singapore, on 24 January, 25 January and 26 January. Flights over these three days will be operated with Boeing 777-300ER aircraft. There is no change to scheduled departure and arrival times.


Singapore Airlines will waive administrative fees/penalties for refund, rebooking or re-routing, for customers holding confirmed tickets issued on or before 21 January 2012, for travel on SQ346/345 from 24January 2012 to 27 January 2012, both dates inclusive. This also applies to KrisFlyer redemption tickets.


The safety of our customers and crew is our number one priority and we will ensure that we take whatever action is needed for the continued safe operation of our Airbus A380 fleet.


For contact details of our offices around the world, please click on the following link: Singapore Airlines
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Old 21st Jan 2012, 15:35
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Can anyone post some pictures or diagrams of the wing components that have cracks in them. I would like to know exactly where they are. Many thanks.
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Old 22nd Jan 2012, 07:16
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The cracks (less than 1cm long) were found on the feet of the wing ribs. The feet attach the rib to the wing skins.

Airbus has traced the problem to the 7449 aluminium used in the wing ribs. 7449 is more sensitive to the way the parts are assembled on the wing. They ruled out flight loads or fatigue as causes.



A few years back, Machine Design reported:

Servosystem deftly handles Airbus wings
MARCH 3, 2005 Staff

With a span nearly as long as a football field at 261 ft, producing a single Airbus A380 wing involves precisely positioning a massive structure to drill, rivet, and bolt approximately 180,000 holes.

During wing manufacturing, six servohydraulic axes move panels measuring up to 111 ft long and weighing 8,818 lb.

That presented a significant challenge for Airbus' manufacturing team in Broughton, U.K., and Electroimpact Inc., Mukilteo, Wash., the prime contractor for wing-assembly automation tools.

Wings are a structural framework of spars and ribs covered with metal panels. The panels consist of a curved, aluminumalloy skin reinforced by stringers that ensure shape and strength. The tricky part is moving assembled panels into four-story high jigs holding the ribs, spars, and leading and trailing edges, for subsequent assembly and fastening.

The huge size and flexible nature of a completed panel up to 111-ft long and weighing 8,818 lb creates a motion-control nightmare. According to Electroimpact's Ted Karagias, handling a wing panel with multiple support points isn't easy. Cranes won't work because the panels distort when suspended, he explains. "Basically you have a statically indeterminate system. The panels twist, bend, and kick as they react to the forces introduced by lifting equipment," he says.

To overcome this problem, Electroimpact devised a manipulator with six coordinated servohydraulic arms to maintain the panel's proper form and precisely control position. "Two of the six arms control the panel's vertical position," he says. "The other four act as slaves imparting a constant programmed force on the wing panel. That way, when the positioning arms are commanded to move up or down, the load-seeking arms follow along to maintain the panel's form."

Each panel-loader arm has four hydraulic-driven axes plus one passive axis, requiring the simultaneous coordination of 24 axes.

Last edited by Machaca; 22nd Jan 2012 at 07:29.
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Old 22nd Jan 2012, 20:44
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Airbus has traced the problem to the 7449 aluminium used in the wing ribs. 7449 is more sensitive to the way the parts are assembled on the wing. They ruled out flight loads or fatigue as causes.
My guess is that 7449 is lighter than the other stuff. What a disaster, it looks like the ribs and the feet are one single milled piece (pos). Not much of a sheetmetal guy but this does not seem like a simple fix.
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Old 22nd Jan 2012, 21:57
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I think you are right about the metal ribs.On the carbon ribs the rib feet are riveted.
Check Machacas first picture upper rh corner.
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Old 22nd Jan 2012, 22:29
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Aluminum Alloy Development for the Airbus A380 :: KEY to METALS Article
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Old 22nd Jan 2012, 22:30
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7449 alloy is basically aluminum + 8.1% zinc and a minor percentage of a few other elements. From what I have read, the molten alloy is cast in the form of large plates from which the ribs are milled to the desired configuration. Heat treating consists of a solution treatment, tempering treatment followed by an over-aging treatment. This gives the alloy higher tensile strength and modulus verses older aluminum alloys. These properties enable the panels to be designed and subsequently milled to thinner cross sections thereby reducing weight.

My guess would be that the cracks first found in holes of the feet could have been a manufacturing problem where the sharp edges were not radiused to the desired specification in some panels. Holes in structural components are significant stress risers points where small cracks can develop under stress and cycles at sharp corners or edges.

The initial assembly of these A-380 wings is a real engineering achievement!
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Old 23rd Jan 2012, 11:51
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machaca; many thanks.

I can remember seeing cracks in VC10s, 707s and 747s, even though some of them looked alarming the engineers involved were usually very sanguine! But the structural engineering seemed rather simpler in those days.

I only flew them and hoped never to break them.
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Old 23rd Jan 2012, 12:34
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I am a non pilot and a non engineer.

Would it be fair to say that the worst case scenario is that:

  1. time consuming and expensive checks will need to be carried out
  2. expensive repairs will be required
  3. these will add weight
  4. this will involve the manufacturer suffering financial penalties from customers

Does anyone assert it will be worse than this?
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Old 23rd Jan 2012, 16:09
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How the Wing is build :
Removed due to no relation to this thread.

Last edited by no-hoper; 23rd Jan 2012 at 23:28.
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