‘Overloaded’ Airbus promises A350XWB will hit its targets

 - July 2, 2008, 11:41 AM

Airbus insists the A350-800XWB will make it to market on time in 2013, despite the company’s failure to close on plant divestments that would have helped pay for $1.5 billion in needed upgrades to key manufacturing sites. Capital investment won’t present a problem, it contends, and lessons learned from the A380 and the Boeing 787 will only improve the chances that the airplane could roll out early, regardless of the pressures of various other projects that must accelerate in parallel.

“Some observers say that Airbus is overloaded,” commented CEO Thomas Enders during a mid-May Technical Press Briefing at the company’s headquarters in Toulouse. “And ladies and gentlemen, in some sense they’re right. Yes, we have a lot on our plate… But I believe we have no alternative; there are no options. We have to find a way, and I think we have found a way to manage most of these issues at the same time.”

Weight Adjustments
Fortunately for Airbus, it seems that options do exist in terms of the A350’s maximum takeoff weight. At press time listed at 245 metric tons (540,123 pounds), 265 metric tons (584,215 pounds) and 295 metric tons (650,352 pounds), respectively, all three variants appear likely to enter service carrying an average of three tons more mtow as engineers adjust their figures to meet range and payload targets. During a June 10 briefing in Toulouse, A350 chief engineer Gordon McConnell said that program engineers had recently updated preliminary loads performed in February, allowing them to build the program’s first global finite element model (FEM) and perform a “bottom-up” weight estimate from proper stress analysis.

Based on its calculations for the -900, Airbus had to raise its empty weight estimate by 2.2 metric tons (4,850 pounds) and McConnell said he expects the similar penalties for the -800 and -1000. The first sizing of the electrical structural network and modifications to the wing accounted for some unexpected weight increases, as did more accurate estimates of needed weight for certain systems after consultation with suppliers, he added.   

Even with the empty-weight increase, McConnell said he expects no change to payload-range capability. However, the weight increase will cause about a one- percent increase in fuel burn, a result McConnell characterized as “not an issue” in terms of performance guarantees to customers.

“Although it’s not result we want, we think it’s the prudent decision to take,” he said, adding that Airbus “constantly” runs studies to meet its target weight.
The OEM has already added composites to the airframe in an effort to cut weight.
The A350XWB now consists of 53 percent composites, rather than the 52 percent Airbus had quoted a year ago. Composites appear in the wings, the center wing box and keel beam, tail cone, skin panels, frames, stringers and doublers, and passenger and cargo doors. The rest of the airframe consists of 19 percent aluminum lithium, 14 percent titanium, 6 percent steel and 8 percent miscellaneous materials.

Apart from its weight issues, the A350XWB project has shown few outward signs that Airbus’ confidence in its timeline will prove misplaced. Not due for detailed design freeze until the end of the year, however, the program remains in its early stages.

Aero Lines Freeze Imminent
This month Airbus expects to freeze the A350’s so-called “aero lines,” or the design’s basic shape and aerodynamic properties. Meanwhile, systems development continues, including the integration of hydraulic circuits that operate at 5,000 psi–the same operating pressure Airbus plans for the A380. Increasing pressure from 3,000 to 5,000 psi allows designers to decrease the size of hydraulic pipes and actuators, which aids access for maintenance crew.

Other systems advances expected to cut maintenance burdens include a two hydraulic/two electric (2H/2E) flight control architecture borrowed from the A380; an electro-pneumatic bleed system; a simplified, three-tank fuel system with no trim tank; four variable-frequency electrical generation systems and an A380 interactive cockpit concept with modular server systems.

Although it has settled on its size of the wing–the wingspan will measure 64.75 meters (212 feet) and the area will cover 442 sq m (4,758 sq ft)–by mid-June Airbus continued to tweak the A350’s aerodynamics, and expected to freeze all wing lines by the end of the summer. Recent changes included a change from a six- to a seven-spoiler configuration and a so-called stream-wise outboard flap motion that maintains an in-line position even when fully extended. Airbus has also settled on the shape and configuration of the winglets.

Meanwhile, the company continues to analyze wind tunnel results related to the tail, but at last report the vertical tailplane had increased in size from 49 sq m (527 sq ft) to 52 sq m (560 sq ft), and the horizontal tailplane has shrunk from 92 sq m (990 sq ft) to 85 sq m (915 sq ft).

Inside the fuselage, Airbus has positioned all water and waste to the rear of the aircraft, and adopted a seven-track cargo loading system supplied by Telair International. Changes to the rear cargo arrangement will allow the addition of two LD3 containers in the -800, and changes in the galley arrangement at Door 4 in the rear of the airplane will allow for four more trolleys than originally specified.

In the cockpit, the integrated modular avionics (IMA) suite will control more systems than in the A380’s IMA, including door and slide controls and the oxygen system. The approach centralizes computing power, reduces wiring and saves weight.
Engineers working on the powerplant design recently released the aero lines for the nacelle. Elsewhere in the powerplant integration effort, Airbus has chosen an electric thrust reverser system by Goodrich. Although an electric system costs more than a hydraulic one, it will save weight and result in more systems segregation and, therefore, safety, explained McConnell.

Meanwhile, Airbus continues to talk with General Electric about the possibility of a second engine choice for the airplane. Now offered with only the new Rolls-Royce Trent XWB, the A350 in its earlier incarnation would have featured General Electric GEnx engines as an option, but once the XWB-1000 emerged as a direct competitor to the 777-200LR and -300ER, GE pulled its offering for fear of cannibalizing sales of those GE90-115B-powered airplanes. Although Airbus still holds out hope that it can find a solution, company vice president of marketing Colin Stuart holds firm to his belief that it can compete without a second engine choice.

“We do think from a commercial viewpoint that a choice of engine is important, but it would not be the end of the world [if there isn’t],” said Stuart. “There are many aircraft that are sold with just a single engine choice. We would like to see a second engine, but that engine would come to this aircraft only if it’s the right engine for the marketplace; if it’s the right engine in terms of fuel consumption, fuel efficiency; if it covers the thrust range that we’re looking at, which covers the seventy-odd thousand up to the ninety-, ninety-thousand pound thrust range.”

That would seem to rule out any proposed option by GE to power only the -800 and -900 and leave the -1000 to Rolls-Royce. Airbus apparently has shown no interest in a partial solution, and has said that the 53,000- to 75,000-pound-thrust General Electric GEnx would not work for the A350, meaning it would require a clean-sheet design that GE, as of last report, has resisted. Airbus’ thrust requirements now stand at 74,000 pounds for the -800, 83,000 pounds for the -900 and 92,000 pounds for the -1000. 

While Stuart conceded that a single engine offering is not ideal, he stressed that the benefit of the third, fully offerable aircraft variant far outweighs the disadvantage of no engine choice. “All of the aircraft types–the 800, 900 and 1000–have orders placed against them,” said Stuart. “That is very different from the Boeing 787 program, where there are, in fact, only two aircraft–the 787-8 and 787-9. We have a very substantial advantage here in that there are three aircraft in this family covering the range from the 767 up into the 777-200s and even 300ER.” [The high-density, short range 787-3, officially the third variant of the 787, would use the same fuselage as the 787-8, but carry 80 more passengers and fly optimum routes of between just 2,500 to 3,050 nm. Boeing also continues its studies on the 787-10, a still not launched “double stretch” of the baseline -8.–Ed.]

Although several customers for the original A350 canceled their orders because of the lack of a GE engine, Airbus did a respectable job of regaining lost sales momentum since it re-introduced the airplane as the XWB at the last Farnborough airshow. Through mid-June, it had drawn firm orders for 374 airplanes from 23 customers, including a firm order announced on June 4 for 12 A350-800s together with an order for the same number of A330-200s from Italy’s Air One.

“We have had the great advantage that the A330–both -200 and -300–has been complementary to the A350XWBs,” noted Stuart. “We’ve been able to place A330s to support the earlier requirements for these 250- to 300-seat airplanes out into the marketplace before the A350 is able to be delivered.”

According to Airbus’ published timelines, final assembly will begin during the first half of 2011, first flight will occur early in 2012, and the 315-passenger -900 would enter service in mid-2013. The 276-seat A350-800 would go into service about a year later and, finally, the 369-seat -1000 would gain certification in the second half of 2015.