UPDATE 5-Factory, design flaws caused A380 cracks

* Airbus says devised simple repair for wing cracks

* Singapore Airlines reports findings on four aircraft

* Airbus insists world's largest jetliner safe to fly

* Analysts reassured by engineering update

By Tim Hepher

DUBLIN, Jan 26 (Reuters) - Airbus blamed a combination of manufacturing and design flaws as more examples of wing cracks arose during checks on the A380, while analysts said its bare-all strategy of addressing the problems in public should limit any lasting damage.

A top executive at the European planemaker said it had established how to repair the cracks found on a small number of parts inside the superjumbo's wings, which prompted European safety authorities to order inspections last week.

Airbus and one of the leading operators, Singapore Airlines, confirmed a Reuters report that more examples of the cracks had been discovered during compulsory inspections.

Airbus moved to shore up confidence in the world's largest jetliner amid a drip-feed of disclosures about cracking on components used to fix the outside of the wing to its ribcage.

"The A380 is safe to fly," Tom Williams, executive vice president of programmes at Toulouse-based Airbus, said.

Williams flew to Dublin to give an unscheduled address at an industry conference to dampen any concerns about safety.

Crucially, he said engineers had ruled out metal fatigue on the youthful aircraft which first entered service in 2007.

Unusually detailed briefings marked a different response from the blowout of an engine on a Qantas A380 in Nov. 2010 when engine maker Rolls-Royce was criticized by the industry and investors for not giving enough information.

"This is a game-changer in getting out information that in the past we weren't told. You can't dismiss these things, but it is not a serious issue and they have a solution at hand," said Howard Wheeldon, senior strategist and aviation specialist at brokerage BGC Partners.

The cracks have tested morale at EADS subsidiary Airbus just as it recovers from years of production delays, having hit its A380 delivery target for the first time in 2011.

The mammoth double-decker was conceived as a European bid to outdo the Boeing 747, but became mired in development problems that caused a near-riot in the French parliament and a rift between France and Germany.

BGC's Wheeldon said engineering flaws rarely affected the contest between Airbus and Boeing in the $100 billion jet market, which is determined more by fuel economy, performance and delivery timescales.

TRIO OF MISTAKES

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 long-range aircraft, listed at $390 million each, and 68 A380s are currently in service.

It blamed the cracks on three errors -- designers' choice of aluminium alloy for some of the 4,000 brackets inside the wings, the use of a type of bolt that strained the metal and a way of closing tiny gaps that put more stress on a handful of parts.

European authorities have ordered inspections on almost a third of the superjumbo fleet, or 20 aircraft, after two types of cracks were discovered within weeks of each other.

Airbus officials said that having understood the problem, they expected most of the aircraft being tested would show similar evidence of cracks and that it had found a simple repair.

Singapore Airlines said it had found cracks on all four aircraft it has inspected so far. One has been repaired and is back in service, spokesman Nicholas Ionides said.

"It seems to me this is part of the growing pains which new aircraft types can experience," said Stephen Furlong, airline analyst at Davy Stockbrokers in Dublin.

"Obviously the negative publicity is not at all helpful. The real problems start when airlines have to ground planes because they are not comfortable with safety issues, which are clearly paramount to an airline's brand. But we're nowhere near that yet with the A380."

Some passengers at European airports earlier this week expressed concern about the cracks while others said they were happy to trust safety inspectors. Airlines have not so far reported any falls in bookings.

Airbus last week dismissed calls by an Australian engineering union for A380s to be grounded.

The cracks first came to light during repairs, lasting over a year, on the Qantas A380 involved in an engine blowout. Supersonic shrapnel tore through the wing and left it resembling what an Airbus official has described as anti-aircraft fire.

At first engineers were unsure what had caused the rib cracks but the initial microscopic flaws led to the discovery of a second and potentially more serious type of crack, some of them up to two inches long, in the central part of the wing.

Executives at a Dublin aviation event said the pace of revelations had provided a need for clarification.

"When they had the second round of cracks, that got more people's attention and a few airlines were asking questions," an executive said, asking not to be identified.

The findings caused concern at the European Aviation Safety Agency which turned down Airbus's request for limited extra time to examine the data and ordered mandatory inspections last week.

The wing is made of both aluminium, the metal used to build aircraft for decades, and carbon composites used in new jets.

Airbus is changing a manufacturing processes to ensure smooth operation until at least the next four-year check-up.

Longer term, it plans to switch to a different alloy, restoring the aircraft to its normal lifespan of 25 years-plus. The wings were designed and built in Britain, which prides itself on state-of-the-art wing assembly. Unions there recently complained about the outsourcing of some work to South Korea.