A380 Wing Repairs To Take 60 Days
Aviation Week.com 06/10/2012
Author: Jens Flottau
Airlines may have to ground their Airbus A380s for 60 days to repair the aircraft’s wings, two A380 operators told Aviation Week on the sidelines of the International Air Transport Association’s annual general meeting in Beijing. Tim Clark, president of Emirates Airline, says around 30,000 maintenance man-hours are required to make the fix developed by Airbus. Airbus is performing the work because Emirates does not have the manpower to handle the task, Clark says.
Airbus says it is also developing a repair schedule that would allow the airlines to perform the work during regular C checks. But that would mean the repairs would be spread out over several years and would make the aircraft subject to a more rigorous check regime.
Lufthansa’s executive board member Carsten Spohr says that with its current fleet of six aircraft, the airline will technically have one of its A380s grounded for one year until all of them are repaired.
Type 2 cracks have been discovered in wing rib feet, the connecting parts between the rib and the wing skin, in most in-service aircraft. Because a permanent fix will not be available until next year, a total of 120 aircraft will have to be repaired. Airbus says about one-third of the 76 in service-aircraft already have incorporated the repairs.
The retrofit entails replacing all of the 23 hybrid ribs (made of a mix of 7449 aluminum and composite) with all-metallic ribs made of 7010 alloy. The rib feet also will be redesigned to strengthen them, and an inspection manhole in the area where the cracking occurs will be strengthened.
There are several causes for the wing-component cracking problem. One is the use of a specific aluminum alloy (7449) and its heat treatment. The alloy saves weight, but it rendered the component more brittle, which caused cracking. Another is in attaching the wing skin to the ribs, where excessive loads were placed on components during assembly. The situation was compounded by a failure to properly account for the temperature-induced material expansion and contraction during operations.
EASA still has to sign off on the fix. That will require validating the proposed repair during flight trials using an instrumented Airbus A380 test aircraft.
To avoid future problems, Airbus will make changes beyond those immediately needed. For instance, ribs 48 and 49, at the outer end of the wing, will be replaced even though no cracks have been found in them because they are made with 7449 aluminum alloy.