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Airbus zeros in on A380 wing cracks with 2 stage fix  

2012-01-28 11:52:01|  分类: English Version |  标签: |举报 |字号 订阅

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January 26, 2012

Airbus zeros in on A380 wing cracks with 2 stage fix - 司古 - 司古的博客

       Airbus says it has devised a two part fix for the fine cracks that are appearing inside some of the wings of its giant A380 airliner that will ultimately add no more than 89 kilograms to the weight of the jet, which can exceed 569 tonnes at takeoff.

Speaking on a bad line from a conference in Dublin, Tom Williams, the executive vice president for programs, went through the three elements of the problem, which he emphasised had created no safety threat to the 68 A380s currently flying.

Those elements were the particular type of aluminium used for a small number of the 4000 L shaped brackets used inside the entire wing of each A380, in which two different small cracks had been discovered in some of the jets, and two steps in their incorporation during assembly that had locked in additional stress which predisposed them to develop visible cracks.

The first of these had been a process in which a fastener had been deliberately forced into a small hole in a way that was calculated to add to the strength of the join, for which the grade of alloy used was wrong.

The second of these steps had been the physical pulling together of two sections of wing skin using a butt strap that was supposed to leave a smaller gap than had resulted because of the unintended additional stresses locked into it during assembly.

Williams said that this choice of material, and the unintended additional stressing of the components on the factory floor had set up a situation where in time the loads applied to the wing over repeated cycles, as well as temperature changes, made the cracks that were being inadvertently built in to the wings visible to the naked eye.

He said he expected these cracks would ultimately make themselves apparent in any A380 as it accumulate more hours of flight and operational cycles.

However he said they would not necessarily be visible when the giant jet reached its first major maintenance check, the C check.

In the interim, those brackets in which the cracks had become visible were to be replaced.  This will add no weight to the aircraft.  In the final fix, which Airbus was in the process of defining, the grade of alloy used in the brackets, and the way in which they were incorporated into the wing would be changed to eliminate building in the extra stresses, and the base of the brackets would be slightly thickened.

However the total weight increase of the final fix, whether in newly built A380s, or in due course in the existing A380s, would only be 89 kilograms.

Williams said no unexpected discoveries had so far been made during the inspections that would be completed by tomorrow Friday of the small number of A380s which had flown more than 1800 times.

A total of 20 of the jets will be inspected for these cracks within six weeks of last Friday, when an airworthiness directive for the jets was issued by EASA, the European Aviation Safety Agency.

All of these jets, and the other 48 now in service, and all of those delivered without the final fix in place, will ultimately require the replacement of wing brackets installed using the original grade of aluminium and to a different procedure.

It will be about four months before any Qantas A380 now in service reaches the necessary number of flights for inspection and replacement of affected brackets under the new schedule set out by the EASA directive.

It should be noted that when the wing of a Qantas A380 was severely damaged by the disintegration of a Rolls-Royce engine near Singapore in November 2010, it kept its integrity for almost two hours under extreme and never expected loads, in which the manufactured flaws later found in some of those brackets didn’t even come into play during the in-flight crisis.


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