EADS (EAD.PA) subsidiary Airbus reported the cracks in January, leading to checks on the worldwide fleet of A380s, which authorities say are safe to fly.

Airbus Chief Executive Tom Enders said the discovery inside the superjumbo's wings, where new lightweight carbon-composite materials and traditional metal meet, showed the difficulty of pushing technical boundaries in the ultra-competitive industry.

"Certainly when it was designed some 10 years ago, it was an innovation. We thought it was a great idea to make wings lighter with a hybrid (of) carbon-fibre ribs and metal ribs. It was supposed to bring a lot of weight reduction, and to a certain extent it did," Enders told a group of aviation journalists.

The A380 was designed in the early part of the last decade. At the time, the aircraft needed to lose weight, in part because of efforts to make it quieter, which required larger and heavier engine fans.

To drive down weight, a decision was made to mix metal and lightweight carbon components inside the wings, but engineers could not tell how this would stand up to extreme temperatures.

"We were confident at the time that we had mastered the technology, that we were selecting the right materials (and) understood their properties and the interface between carbon fibre and metal," Enders said.

"We found out the hard way that we didn't know everything we should have before taking this decision."

The willingness to tackle the issue head-on in his last major media appearance before stepping up to chief executive of parent EADS later this month, contrasts with the industry's usually conservative tone and marks efforts to draw a line under a damaging episode for the world's largest civil planemaker.

People familiar with the matter said EADS and two groups of auditors had been brought in to assist with an investigation which Enders launched in February.

Airbus will also be looking for certainty that similar problems could not crop up elsewhere.

NEW TECHNOLOGY

The upheaval comes at a time when Airbus and rival Boeing (BA.N) are investing billions of dollars in a more radical technological leap towards new lightweight aircraft such as the Boeing 787 Dreamliner and the future A350.

Boeing was hit with composite-related fuselage problems on its 787 Dreamliner and had a potentially serious fire on a 787 test flight.

Both the 787 and A380 have been declared airworthy but authorities have ordered a tighter timetable of regular checks on the A380 until a permanent fix is introduced.

A350 programme head Didier Evrard said extra fatigue tests would be carried out on the company's future A350 test planes during development.

The A380 cracks were found in L-shaped components called rib feet, which connect the wing's skeleton to the outer skin. Airbus said it had decided to change the type of aluminium alloy used for the parts to one less brittle.

It takes a year for completely fresh wings to work though the production system, and it will not be before 2014 that entirely fresh aircraft will start rolling off assembly lines.

Meanwhile, the cost of the mistakes made a decade ago under a mainly different management team appears to be rising.

Last week, EADS (EAD.PA) took 158 million euros of provisions for the cost of retrofitting planes already built, while getting ready for a permanent fix in 2014.

Added to money paid out of an existing provision for warranty repairs, the cost so far booked by EADS is 263 million euros, but figures supplied in technical media briefings this week suggested the cost could rise by another two-thirds.

Provisions cover the 71 A380s in service by the end of the first quarter, equivalent to 3.7 million euros per plane.

Executive vice-president Tom Williams said the total of A380s in the pipeline that would likely need repairs before the new solution made retrofitting unnecessary, was 120.

That implies a further 181 million euros of costs to be accounted for, on 49 aircraft at the same rate per plane.

Developed at an estimated cost of 12 billion euros in Britain, France, Germany and Spain, the A380 has room on its wingspan of 79.8m (261ft 10in) to park 70 cars.

Airbus has sold 253 of the double-decker aircraft, listed at $390 million each, and 74 A380s are in service.

Airbus officials said they were confident the A380 would overcome the problems, and sales chief John Leahy reiterated plans to sell 30 superjumbos in 2012.

(Editing by David Hulmes)

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