The latest high-lift technology for the A350 XWB's wing promises to reduce complexity and better deliver low-speed performance, while also offering significant fuel savings for airlines.
High-lift systems use devices such as flaps and spoilers to create more lift from a wing, most notably during take-off and landing. While Airbus has generally been a leader when it comes to designing these mechanisms, the A350 XWB's state-of-the-art system adds more intelligence to the wing, allowing for greater dynamic response and flexibility.
Airbus flaps have been supported on beams that are attached to the wing. These beams have titanium rails with carriages, which slide up and down to move the flap whilst rotating around a rear link. This had proved to be the best trade-off between weight and takeoff performance. However, the track/carriage mechanism is particularly complex, and it was important to save on weight, costs and maintenance for the newest member of Airbus' jetliner family.
The solution was found by integrating a wing's flap and spoiler movements using a "software coupling." Whichever way the flap may be deployed, the computer-controlled spoiler automatically moves into the most efficient position. Early wind tunnel tests on a modified A320 wing have proved the viability of a software-controlled spoiler-flap interlink, demonstrating an advantage in lift without any detriment in drag.
The new high-lift flap, which has been patented by Airbus, is a dropped hinge design and consists of a beam with a rotation point. Designated as the "advanced dropped hinge flap," it is simpler than a conventional flap and requires less moving parts, resulting in a half tonne weight reduction. It is also easier and less costly to maintain.
The advanced flap concept provides benefits during cruise as well. Rather than having a static wing profile, the new flap allows varying camber (wing profile) options as the aircraft burns fuel and loses weight during flight. Drag can be reduced by up to two per cent at high gross weights, resulting in considerable fuel economies. Moreover, weight savings on the order of half a tonne for the wing box are feasible by using differential flap settings to alleviate manoeuvre loads.
The A350 wing configuration with its new high-lift system has performed well in wind tunnel tests, and the programme is now entering its verification and validation phase. Wind tunnel tests continue, and the final flap shape will be frozen by July 2008 - with the structural test plan completion being reached by September 2008.