With the A380 very-large airliner firmly established in production and airline operation, Airbus is now hard at work on its next project: the three-model A350XWB twin-aisle twinjet family. It is about to begin production detailed design for
the mainly carbon-fiber aircraft, which is competing against the Boeing 787 and which Airbus claims also could replace the larger Boeing 777.
Manufacturing of production tooling is already under way, as is development of aircraft systems and the passenger cabin, according to A350 program head Didier Evrard. Unveiled at the 2006 Farnborough airshow three years ago, the new design is a wider-cabin reworking of an earlier two-model A350 proposal, based on the A330 that makes extensive use of composite materials.
As Boeing 777 sales benefited from a fuselage broader than the 222-inch “magic-dimension” width of Airbus A300, A310, A330 and A340 models, so Airbus now seeks a competitive leap-frog advantage with an A350XWB “extra widebody” cross section “effectively about five inches wider [than the 787] at all measurement heights.” Airbus believes the A350XWB will accommodate 10-abreast seating–like the 777–which was not possible on its earlier models.
The A350-900 fuselage, wings and empennage aerodynamic lines, systems architecture and cabin design (except rear galley) were frozen late last year. Final refinement of pylon and nacelle lines is on track for design freeze, according to Evrard. He said similar freeze points will be reached for the shorter body A350-800 in about six months and for the stretched -1000 variant in the second quarter of 2011.
Tooling, jigs and long-lead items have been launched, and the design performance and weights given a year ago remain unchanged, he said. Airbus plans to begin parts manufacture, cut the first metal (for the tailplane cruciform) and lay up the initial composite fuselage panel later this year. Assembly of the center wingbox (CWB) is scheduled to follow in early 2010, Evrard said. Before then, validation of the A350’s electrical structure network is planned in a test fuselage section.
The European airframer expects to begin final assembly of the first A350 in about two years. Testing of static and fatigue specimens should be initiated around the end of 2011, ahead of first flight in early 2012 and service entry in mid-2013, according to a schedule Airbus released last month.
Before the A350 maiden flight, the company will use a digital mockup, as well as synthetic and real testing of system functions in an effort to ensure reliability, since many airframes, assemblies and subassemblies will be in production and Airbus wants to minimize modifications arising during flight test. “Maturity at first flight is a challenge,” said Evrard.
The company will use five aircraft in the planned 3,000-hour, 15-month flight-test and certification program and plans to get them “into the air very quickly” after the first flight. Two test A350s will have complete interiors: No. 2 will be used to check aircraft-definition freeze processes and to demonstrate cabin customization, while No. 5 will be used for evacuation trials and long-haul performance. The sixth aircraft will be the first to enter service. Other cabin-related testing will cover interior sound levels and sound insulation and damping.
The A350 airframe, including undercarriage, will comprise mainly carbon-fiber reinforced plastic (CFRP) composite material (53 percent), aluminum/aluminum-lithium alloys (19 percent), titanium (14 percent) and steel (6 percent). CFRP is being used for its fatigue strength and noncorrosive properties in the A350 wings, CWB, tailcone, fuselage skin panels, frames, stringers and doublers, as well as passenger and cargo doors. Titanium is employed for high-load fuselage frames, door surrounds, engine pylons and undercarriage, all areas where corrosion resistance is important.
Airbus has made extensive use of computational fluid dynamics modeling to develop an advanced wing, which will use differential flap settings and variable camber for optimal performance. Outer and inner flap sections will automatically deflect differentially in both takeoff and cruise configurations, or in unison in cruise, to alleviate flight loads on the wing and to reduce weight.
Systems for the A350 are being designed for simplicity and efficiency: flight controls will have electrical backup for better dispatch reliability; there will be just three fuel tanks to reduce the number of pumps and valves; and the hydraulic system will have two circuits operating at 5,000 pounds per square inch pressure. On the flight-deck, the six 15-inch display screens will be identical and interchangeable, which Airbus claims will provide an 80-percent saving in spares and direct maintenance costs compared with those of the A340.
An innovation in flight operations, according to Evrard, will be the use of advanced continuous-descent approach techniques providing full management from cruise level to the runway. Evrard said this offers the prospect of 3 to 6 dB reductions in noise below the flight path at between 30 and 7.5 nm from touchdown.
The Rolls-Royce Trent XWB, the exclusive powerplant for the A350, will provide thrust levels of 75,000 pounds, 84,000 pounds and 93,000 pounds for the A350-800, -900 and -1000 variants, respectively. Offsetting higher aircraft weights, these latest ratings represent a marginal increase from the levels confirmed last year and follow reductions in power quoted in 2007.
Current thrust is about 1,000 pounds greater than the power requirements given before Airbus raised empty and maximum takeoff weights in 2008 by between 4,850 pounds and 6,615 pounds. Two years ago, ratings had been cut by 1,000 to 4,000 pounds, depending on the variant.
Airbus has established a demonstrator program involving two A350 airframe barrel sections to support development of analysis methods and tools, as well as manufacturing processes and certification of the CFRP structure. Evrard said CFRP fuselages behave differently from those of traditional light alloy materials. Airbus needs to check the electrical structure network introduced to carry electrical current through the composites airframe.
One area that remains to be finalized is the A350 rear galley. Evrard said the manufacturer was challenged by customers about a lack of workspace, so it has been reworked to provide the required space and to accommodate an appropriate number of food trolleys.
According to Airbus, the A350 program will build on the A380 experience and customers will enjoy reduced maintenance requirements. The schedule is expected to call for no line-maintenance intervals less than 10 days, only technical-service line-visits below 1,200 flight hours, base checks every 36 months and structures checks every 12 years. This would equal a 10-percent reduction in A350-900 airframe maintenance costs compared with those of the Boeing 787-9.