Qantas Airways and Airbus engineers faced both technical and logistical challenges in restoring its first A380 back to virtually brand-new condition after the aircraft's uncontained engine failure in November 2010.
The aircraft, which has the registration VH-OQA, suffered the mid-air failure after take-off from Singapore. Repairs were completed almost 18 months after the incident, and the aircraft returned to Sydney on 22 April.
"The repair-rebuild was unique in terms of the quantity and the size, but not the philosophies. Overall the repair principles used throughout are based on standard practices as performed regularly by the experienced Airbus teams, with the main differences here being related to the larger scale," says Airbus.
"The challenges and achievements were not just technical but logistical, especially in having to move such large parts around the world, out of normal sequence. These had to be packed, shipped out and reassembled in Singapore in somebody else's hangar."
Airbus says that it undertook a damage assessment as soon as it was granted access by the authorities. This first stage took six weeks, during which a decision was made that the aircraft would be repaired instead of being written off, says Qantas integrated operations centre head Alan Milne.
It was then determined that the aircraft could not be temporarily repaired and returned to a home base or maintenance centre due to the complexity of the project, and because the repair and testing required would have taken just as long as the complete rebuilding work.
Airbus provided a repair proposal in February 2011, and it signed a contract with Qantas in May 2011 that led to the second phase of the project when the A380 had to be stress-jacked. A separate contract was signed with SIA Engineering for hangar access - initially for the bespoke 'Number 6' A380 hangar at Changi airport for the stress-jacking phase, and subsequently the Number 1 Boeing 747 hangar for third phase of the project for completion activities, which did not require the aircraft to be stress-jacked.
"We had to get the aircraft back in factory condition," says Airbus director of customer support and services Derek Blackham. "The key area of Phase 2 was when the aircraft was stress-jacked, it had to be at a zero-g state so that there is no undue stress during the repairs."
Airbus loaded the dedicated stress-jacking equipment into 19 lorries and began to ship them to Singapore before the agreement. The aircraft was rolled into hangar 6 on 6 July 2011 and was rolled out on 22 October - a day before the scheduled roll-out date and six months after the agreement was signed. Work then continued either outside on the apron or in the Number 1 hangar. Around 70,000 production man-hours were used for the repair, says Airbus.
The repairs entailed replacing the A380's damaged inboard left-hand Rolls-Royce Trent 900 engine and pylon. All damaged internal stringers and equipment were repaired or replaced, and all damaged flaps and fairings were replaced.
The fuselage's glare material and metal panels were repaired by blending where impact had occurred, and the electrical wiring system for the port wing was completely replaced. A section of the top skin was removed and a specific repair plate machined and installed.
"For this, Airbus performed [three-dimensional] laser-scanning so that the upper wing geometry was maintained throughout the repair, and in accordance with the A380's 3D digital design database. The result is a totally flush surface for the wing airflow," says the airfamer.
A specific section of the front spar was newly manufactured, customised and machined to fit the top skin repair, replacing the damaged section. Airbus says that the A380's spar design allowed the entire section of damaged spar to be removed by simply unfastening it at the natural production joints and then re-fastening the new replacement section into position.
For the lower skin panel repairs, Airbus says that external butt-straps on the lower skin of rib 6 and rib 13 are the only visible evidence of the repair. The butt straps are the joint external "doubler", a reinforcement where the two plates join. The profile is blended for a smooth aerodynamic surface to the airflow, says Airbus.
The total weight added by the repairs was 94kg, far less than the 250kg allowed for in the original agreement between Qantas and Airbus.
"This was achieved due to 'as-new' replacement parts being used wherever possible. This very small additional weight impact was a considerable achievement," says Airbus. "The aircraft's overall performance - range and efficiency - is expected to be unaffected."
After the repairs, Airbus and Qantas crew conducted a comprehensive ground and flight test of the aircraft. The standards would not be less than specified in the Airbus production aircraft test manual, they said. The tests included static checks, engine runs, taxi check and rejected take-off, and a technical flight. Qantas also performed a performance measurement flight in Sydney with the support of Airbus flight test engineers.
The entire tab of A$139 million ($144 million) was picked up by insurance companies. Another A$95 million came from Rolls-Royce, which supplied the Trent 900 engines, as compensation.
The repair was audited by Airbus, Qantas, Australia's Civil Aviation Safety Authority, and Organisme pour la Sécurité de l'Aviation Civile throughout the process. There were about eight audits in total, with no significant findings.
After a handover ceremony, the aircraft took off from Singapore's Changi airport on 21 April as flight QF32 - the same number it used when the incident happened. It landed in landed in Sydney on 22 April, and will return to active service on 28 April on the Sydney-Hong Kong route.
"She's running a little late, by about 18 months," Qantas chief executive Alan Joyce said before the flight to Sydney. "But looking at the repairs, it has been worth it. She is almost brand new."