Airbus admits the slow pace of automated wing-drilling on the A350-900 forced the latest schedule slip to service entry, but the airframer believes it is overcoming the problem and aims to minimise the impact on the maiden flight.
A350 programme chief Didier Evrard tells Flightglobal that, in addition to the airframer's having to resort to manual drilling at its Broughton plant, the locking of jigs while the automation issue was addressed has had a knock-on effect on subsequent wing sets.
"The robot was not working properly, the software was not optimised," he says, and the drilling "took much more time".
The domino effect on production of the prototype fleet left "not enough margin to catch up", he adds, and led Airbus to push back entry into service to the second half of 2014.
Airbus has adopted a concept in which it builds the wings horizontally and the Broughton facility is able to assemble three sets of wings in parallel.
The plant is currently handling the wings for the static airframe, MSN5000, as well as those for the first flying aircraft, MSN1, plus a test wing designated 'EW' being built to accelerate testing through a separate damage-tolerance exercise.
Broughton will probably ship these to their various stations - the MSN1 wing to Bremen for high-lift system work, and the MSN5000 wings to the final assembly line in Toulouse - around the same time, August-September.
Drilling on the EW test wing, bound for a rig in Germany, shows that the automation issue is becoming manageable, says Evrard. "For the next sets of wings we won't have the same problem," he says. "We've already tested the new [drilling] software on one wing and it's much more efficient."
The next wings in the sequence will be those for MSN3.
While the wing production has proven difficult, Evrard says the airframer is making "good progress" on the other sections of MSN1.
Airbus started power-on work on 23 July. MSN1 is already equipped with electrical distribution and avionics systems and power-on tests will continue through August, ahead of the next main sections which will arrive in September and Evrard says the MSN1 fuselage will be assembled in October.
"We have a good grip on the first flying aircraft," he says. Evrard believes that, despite the wing-drilling problem, the airframer will be able to claw back some of the time in order to reduce delays to first flight - still intended for mid-2013.
"Today, I think that we can catch up," he says. But he reiterates that Airbus's strategy with the A350 is to ensure maturity of components at each crucial stage, to avoid out-of-sequence work on the final assembly line.
The engine flight-test programme entered a second phase on 26 July using an upgraded Rolls-Royce Trent XWB powerplant. Evrard says that the first phase, involving over 70h of tests using the A380 testbed, generated "very good results".
"On the positive side there's good progress on the first sections of the aircraft," he says, including the complex section 15 centre fuselage, produced by Spirit AeroSystems, which had previously been a source of concern. While Evrard "can't say everything is fully bridged" regarding the production process, he is confident that the section for MSN1 will be ready by the end of September.
Airbus's attention is focused on the first flight - preparing MSN1 and the static airframe in Toulouse, and performing virtual flights using simulation - as well as demonstrating the integrity of the manufacturing process and the readiness for the initial low rate of production.
After MSN1 and MSN3 the prototype assembly effort will turn to MSN2, the first cabin-equipped test aircraft. Another non-cabin aircraft, MSN4, will follow before the cabin-fitted MSN5 is assembled.