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Cracks appear in public understanding of metal fatigue

Updated with Airbus statement

Something of a case study in aviation media communications is taking shape, or rather, cracking up, in relation to ‘minor’ cracks found in the wings of some Airbus A380s, including the Qantas one that remains under repairs at Singapore’s Changi airport following its mid-air engine disintegration drama in November 2010.

This is a development that can be seized on for all sorts of agendas, well meaning or otherwise, and lends itself to anything from a screaming tabloid headline to a few paragraphs in News-in-Brief, even though it turns out to be a manufacturing issue that comes with no safety of flight implications.

It was a story that should be neither dismissed as irrelevant, nor seized upon to forbid the loathsome, ugly, un-American, despicable, French, flying machine ever taking off with another passenger’s life at risk again ever.

But as usual, both types of story will appear, if not in Australia, anywhere else that is having a slow news day.

The truth about airframe cracks and manufacturing anomalies, which is what this is about, is that in the case of every passenger airliner entry into service since the original ill-fated Comets, such issues, serious and non-serious, have always arisen.

There are thousands of service bulletins, and at the least, many hundreds of their more urgent counterpart, airworthiness directives, that have been issued and remain in continued effect in relation to structural cracks or material failures appearing in every engine/wing combination known to the jet age.

In relation to fatigue they reflect the reality that the wear and tear of pressurization cycles and landings will cause cracking in airframe and engine structures, including engine pylons, wheel gear, window frames, fuselage joins, and in the skin or surface of wings and the stringers that connect panels to the internal structure.

The trick is to catch the ones that might become serious, or were not predicted by the fatigue modelling and testing of an airliner type that is a part of its certification process.

When they are found they may require immediate rectification, through an airworthiness directive, which will usually become a part of a set of ADs devised to deal with a particular issue with more and more precision as inquiries progress, or the incorporation of a remedial process into those already set down for a regular service interval, which is preset to a certain number of cycles or hours, and which become more invasive and costly as a particular airframe ages.

In fact the whole regulatory process for dealing with structural cracks because of the early history of airliner design disasters, like that of the Comets, the Vickers Viscounts, the Vickers Vanguards, Lockheed turbo-prop Electras, and more recently, aged Boeing 737s and 747s, is as crushingly boring as watching grass growing.  But it works.

Every jet every reader ever flies on will have developed  crack issues or alerts of some nature, as well as a schedule for their oversight and if necessary, removal or repair, within at least a few years of service.

The Airbus statement says:

Airbus confirms that very small cracks were found on some non-critical wing rib-skin attachments on a limited number of A380 aircraft.

We have traced the origin to a material-related manufacturing issue and developed an inspection and repair procedure which will be done during routine, scheduled, maintenance checks.

This is not a safety issue. Aircraft performance is not affected. Any fix, if necessary, can be done during regular (4 year) maintenance.

Airbus has informed all A380 operators. The European Aviation Safety Authority (EASA) is fully aware of the issue and in line with the Airbus approach. Airbus emphasises that the safe operation of the A380 fleet is not affected.

 

The Qantas A380 incident near Singapore which led to the repair process which found evidence of this unrelated manufacturing anomaly, saw its wing pierced and seriously damaged in many places  by a Rolls-Royce engine that had a fault the maker didn’t tell Qantas about while it set about rectifying it to its own schedule. The advanced load transfer capability of the A380 composite/alloy wing design kept it intact for nearly two hours. In earlier Airbuses, or Boeings, such damage might have led to rapid wing failure and a loss of control and a major air disaster.

This document, prepared for Airbus for A380 customers, deals with the actual damage suffered by the wing, and was exclusively published by Plane Talking last year soon after the incident and read by hundreds of thousands of people.

The first reports of the small cracks found in the wings were naturally associated with Singapore incident, but they are unrelated.

The Qantas A380 incident remains a testimony to an outstanding design, as well as exceptional professionalism by the pilots.

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  • 1
    Magoo
    Posted January 6, 2012 at 5:17 pm | Permalink

    Good context Ben. Now watch tomorrow’s morning shows build it up way out of control!

    Cheers

    Andrew

  • 2
    Matthew of Canberra
    Posted January 6, 2012 at 6:25 pm | Permalink

    As I understand it, planes are carved from solid blocks of a particularly firm sort of cheese (with engines glued on, obviously). They have no internal structure worth mentioning. So any crack that might form anywhere on the body could easily go *snick* and lead to a wing just flaking off, like a bit of parmesan might.

    They’re not at all like, for example, cars – which are horribly complex things. Sometimes quite nasty dents on the outside (or even, I’ve heard, broken tail-lights or entirely missing side-mirrors) don’t necessarily lead to a situation where the vehicle can suddenly explode, flip upside down or unexpectly open all the doors and chuck the passengers out at highway speed.

    Nonetheless, I can’t imagine that any journalist would ever dare to drive their car without checking every fluid level, tyre pressure or performing a visual inspection. And a hairline crack would obviously see the vehicle grounded until a flat-bed truck can be hired to take the vehicle for repairs. And even that takes into consideration that car accidents are so much rarer (and statistically less fatal) than in-flight incidents.

    I hope people understand that I’m being a bit silly.

  • 3
    Matthew of Canberra
    Posted January 6, 2012 at 6:26 pm | Permalink

    Anyway … do they still USE metal in planes?

  • 4
    Uwe
    Posted January 6, 2012 at 9:17 pm | Permalink

    metal?
    No it’s all cheese carved from the moon these days ;-)
    Think about why airplanes are so expensive ;-?

  • 5
    comet
    Posted January 7, 2012 at 2:48 am | Permalink

    How do you explain the shrill coming from Steve Purvinas of The Australian Licensed Aircraft Engineers Association? Today he got on the television news and called on every A380 to be grounded immediately to protect the travelling public.

    This is supposed to be a professional body representing professional engineers. If engineers don’t understand the issue, then who does?

  • 6
    Uwe
    Posted January 7, 2012 at 9:30 am | Permalink

    @comet
    looks like a biting reflex.

    He sees cost driven workmanship issues while
    Airbus attributes to specific material selection.

    Quite usual that politicos ( and imho Steve Purvinas is a politico ) try to
    float their boat a bit upriver with any flood splashing along.
    Any press is good press.

  • 7
    Matthew of Canberra
    Posted January 7, 2012 at 7:17 pm | Permalink

    Uwe @4

    That’s just silly. There’s no air in space, so how would they fly back? Try to be realistic.

    @6

    I wonder if there are teams of people at boeing and EADS, whose job it is to cheer when something goes wrong with one of the opposing team’s planes.

    Personally, I think modern jet airliners are incredible. Look at what that kafooming engine did to the structure of that qantas 380 … and the thing just kept flying. Takes a kicking, and keeps on ticking. Ok, sure, there was almost certainly some very experienced, astute piloting going on as well. But wow.

    People need to think more (or maybe less) about the sheer miracle of traveling nearly 1000km/hr, 10km up in perfect safety (if not always perfect comfort). Then the plane lands, turns around and does it again. And again. And again …

    I’d much rather be on a modern jumbo with something going wrong than, say, on a roller coaster (I went on the mad mouse in adelaide once and it offended my common sense) … or possibly even driving in rome.

  • 8
    Uwe
    Posted January 7, 2012 at 8:36 pm | Permalink

    hail, Matthew of Canberra,
    1:
    if it smells cheesy and looks cheesy there is a good chance it is cheesy ( or a humorous quip ). Difficult concept, I know ;-)

    2:
    I’ve had discussions about this and the consensus seems to be that articles might on occasion be “bought” or an aiding template provided but commentary then is from “Boeinginista” or “Airbussiers” in selfemploy.

    Now understand that my commentary number 6 wasn’t in any way derived from sillyness or fanboism.

  • 9
    NeoTheFatCat
    Posted January 8, 2012 at 9:15 am | Permalink

    The problem with most aircraft safety reporting, is that it assess risk using consequence only and disregards likelihood and mitigation. Therefore, if something ‘might’ happen that has disastrous consequences then it’s OHMYGODTHEPLANECOULDHAVECRASHEDANDKILLEDEVERYONE. If something does happen, and good aircraft and systems design together with pilot skill managed it, then it’s OHMYGODTHEPLANECOULDHAVECRASHEDANDKILLEDEVERYONE.

    It makes a good news article I guess…

  • 10
    Zarathrusta
    Posted January 8, 2012 at 8:00 pm | Permalink

    @Matthew of Canberra
    I’ve been on the Mad Mouse with an overweight friend and I truly thought our car might be thrown off and we might die. It was really terrifying. Had to see my chiropractor to put my neck back in.

    I can only say that the press statements by the Aircraft Engineers Union, whatever they are called, lost them a hell of a lot of support from me. I will question everything they say in future. The parts with the cracks, from other news reports, attach the skin to the wing skeleton. As such they are more like the rings on a curtain rod, not the rod or brackets itself and just as the curtain stays up with 1 or 2 rings missing, the failure on 1 or 2 of these things might make the wing skin buckle a bit but it will not shed the skin nor stop the wing functioning. The damage will be visible and it will be repaired of such a failure occurs.

    Let’s not forget that this is the wing design and build that survived an enormous explosion right under it with 2/3 kg of shattered turbine disk going right through it at the speed of a bullet. The scare mongering about this discredited both the union and the media.

    What I’d like to know is how much follow up has occurred about these accusations by Al Jazerra: http://www.aljazeera.com/programmes/peopleandpower/2010/12/20101214104637901849.html

  • 11
    SBH
    Posted January 9, 2012 at 9:25 pm | Permalink

    Thanks Ben, very useful and I must say comforting. Still us plod may trust manufacturers and airlines more if they were less prone to cover up, obfuscate, collude with governments to thwart investigators and generally just lie to us.

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