Airbus will have to retrofit 120 A380s to resolve a problem with wing component cracking before a permanent fix will be implemented on new-build aircraft.

The aircraft maker has already delivered 74 A380s, but the total number in need of retrofit will grow to 120 aircraft because of work already in the production system, says Tom Williams, Airbus’s executive VP-programs.

Airbus has developed two fixes it says will permanently deal with the cracking of some rib-feet, which has already resulted in an airworthiness directive requiring enhanced inspection intervals and fixes where component cracking is found. One solution addresses the retrofit fix while the other alters the production process so the problem never occurs. The fixes should restore the aircraft to 19,000 flight cycles and regular inspection intervals, Williams says.

Airbus expects the cost of resolving the situation to top €260 million ($327 million).

There are several causes for the problem. One was the use of a specific aluminum alloy and its heat treatment; the alloy delivered weight savings, but the component was more brittle, causing cracking. Another problem occurred in attaching the wing skin to the ribs, where excessive loads were placed on components during assembly.

The problem was compounded by a failure to properly account for the temperature-induced material expansion and contraction during operations.

The European Aviation Safety Agency still has to approve the repairs, which Airbus will need to validate inflight trials using an instrumented Airbus A380 test aircraft, which Williams expects to be flying in the fall.

To avoid future problems, Airbus has decided to make changes beyond those immediately needed. For instance, Rib 48 and Rib 49 at the outer end of the wing will be replaced even though they have not shown cracking because they are made of the same alloy that has caused problems. The ribs will be replaced with ones made of a more traditional alloy.

Airbus is now deliberating how it will implement the retrofit and is in discussions with its airline customers. Options include parking the aircraft several weeks to fully install the fix, or a phased enhancement during several C-checks. The repair comes with a relatively modest 90 kg weight penalty.

Some airlines also may defer taking delivery of the aircraft until the permanent solution is installed.

In the retrofit, all 23 hybrid ribs will be replaced with all-metallic ribs, and the rib feet will be strengthened. An inspection hole in the area where the cracking takes place also will be strengthened.

The permanent fix, which replaces all the composite ribs with metal ones, should be available in early 2013; the change should not affect the aircraft’s weight.

Airbus also has adapted its A380 design process to improve its finite element modeling techniques to catch such problems earlier, and is applying more stringent measures to the development program for its A350 widebody. In most cases, the materials are different, but where the aluminum alloy involved in the A380s has been used it has been replaced with aluminum lithium.

Meanwhile, Airbus is gradually seeing improvements in dispatch reliability of the A380 to 97.6%, and as high as 98.6% in March. “It is going in the right direction,” says Airbus Chief Operating Officer for Customers John Leahy, although he acknowledges this reliability rate still trails that of the company’s other aircraft products.

Leahy also hopes to book 30 A380 orders this year, but says that is “a stretch.”

The aircraft maker next year expects to deliver the first A380 to Emirates Airline with 575 metric tons maximum takeoff weight (MTOW), which boosts the aircraft’s range to 8,500 nm.

Also becoming available is a 490-metric-ton maximum takeoff weight version, which complies with more stringent noise requirements and should allow airlines like Emirates to operate early-hour flights at slot-constrained airports, such as London Heathrow.

Emirates already has signed up to take a 510-metric-ton MTOW A380, to be used in regional routes with about 650 seats.