How Airbus Is Debugging the A350
A few times a month, Airbus Flight Test Engineer Patrick du Ché stands up from his desk, takes off his jacket and tie, walks to the coat rack in the corner of his office, and slips into a set of fire-resistant underwear, a bright-orange flight suit, and sturdy black boots. Then he walks down two flights of stairs and out onto the tarmac of Toulouse-Blagnac Airport in southern France. There, rising above a fleet of newly painted A320 short-haul jets, is an Airbus A350-XWB long-range widebody airliner—the very first of its kind. Sleek and nearly all white except for the lettering along its flank and the swirling blue-on-blue Airbus logo on the tail, it carries the official designation MSN001. Last May, in a modest employees-only ceremony, the final assembly line workers formally handed the plane over to the Flight Test Department. Or, as du Ché sees it, “They handed it to me.”
As a flight engineer and head of the department, du Ché gets first pick of the test flights. Although he describes himself as risk-averse, he tends to choose those he calls the most “interesting,” which means at the edge of the plane’s capabilities, where if something goes wrong, it could destroy the plane. Since June, du Ché and his colleagues have flown at the A350’s maximum design speed; conducted aerodynamic stalls; and taken off so slowly that the tail dragged on the ground.
Each test flight is operated by a crew of two pilots and three flight engineers, who monitor the stream of data flowing from a multitude of sensors into a bank of computers installed in the middle of the cabin. Du Ché’s station is behind the co-pilot’s on the right side of the cockpit. On the seat is a parachute. If things should go terribly awry and the crew needs to evacuate, a bright-orange railing leads them from the cockpit door to a hatch in the floor above the forward baggage compartment. By pulling a lever, the crew can trigger a set of explosive charges that will blow a hole in the right side of the fuselage. They can then leap down a slide, through the hole, and into the air. That’s the idea, anyway. Says test pilot Frank Chapman: “If the plane is tumbling out of control, would you really be able to get out?” He shrugs.
Airbus must prove to itself, regulators, and its customers that the A350 works not only well but also within a hair’s breadth of perfection. What began eight years ago as a plan for Airbus’s first jet built mainly with lightweight composites is now a complex assemblage of millions of parts governed by millions of lines of computer code. The company allotted itself a year and a half to make sure it all works.
Beyond a catastrophic failure, the company desperately wants to avoid the kinds of problems that have plagued its perpetual rival, Boeing, and its 787 Dreamliner. After several production fiascoes, the 787 endured further problems after its entry into service, including lithium-ion battery packs that burst into flame. Earlier this year the Federal Aviation Administration and its counterparts around the world grounded the Dreamliner for three months, the first time the U.S. agency had done so in more than 30 years.
Airbus doesn’t have to look to Boeing for cautionary tales. A decade ago a simple design miscalculation of the A380 superjumbo airliner required that miles of wiring be pulled from half-built planes and reinstalled. Along with engine supply problems and other mishaps, the snafu set production back more than two years, leading to $6 billion in losses and a wholesale corporate reorganization. “We have tried to draw on the lessons of what didn’t go well on the 380,” says Airbus Chief Executive Officer Fabrice Brégier. “We have changed our whole organization.”
The company has put unprecedented resources into debugging the A350—“de-risking,” as it’s called. Success could help Airbus dominate the market. Over the last 15 years, Airbus and Boeing have evenly split the $100 billion world airliner market, with each now holding a 5,000-plane backlog of orders. If all goes well with the A350 program, says Brégier, the airliner “will be 40 percent of our revenue, probably for a minimum of 20 to 30 years.” The aircraft is already responsible for 12,000 jobs around the world, a figure that will rise to 16,000 during peak production. “It’s a big investment,” Brégier says.
The engineering risk with the A350 isn’t that it will have chronic, life-threatening safety problems; it’s cost. Aeronautical engineering has come a long way since the de Havilland Comet, which suffered three in-flight breakups after its introduction in 1952 and was withdrawn from service. Today’s commercial airliners are amazingly safe; neither the A380 nor the 787, for all their problems, has been involved in a fatal accident.
A modern airliner is a semi-autonomous system. Planes have an electronic nervous system that constantly monitors thousands of parameters internally and externally, communicates autonomously with navigation and maintenance networks around the globe, and assesses whether its pilots are flying it safely. A pilot who pulls back on the stick doesn’t directly pull up the elevator on the tail of the aircraft, but rather sends a request to the plane’s computer, which then decides how much to move the rudder and other control surfaces. If a pilot tries to fly in a way that’s clearly dangerous, such as going into an aerodynamic stall, the plane won’t let her. “A modern aircraft is an order of magnitude more idiot-proof than 30 years ago,” says Mark Cousin, head of system integration for the A350.
The challenge, Cousin says, is that “in a complex system there are many, many more failure modes.” A warning light in the cockpit could alert a pilot to trouble in the engine, for instance, but the warning system could also suffer a malfunction itself and give a false alarm that could prompt an expensive diversion or delay. Any downtime for unscheduled maintenance cuts into whatever savings a plane might offer in terms of fuel efficiency or extra seating capacity. For the A350 to be economically viable, says Brégier, “the airlines need an operational reliability above 99 percent.” That means that no more than one flight out of every 100 is delayed by more than 15 minutes because of technical reasons.
To ferret out the flaws in an airplane, Airbus technicians have come to depend on sophisticated computer systems. These, too, can introduce problems. Like the A350, the A380 superjumbo was designed entirely on computers, but engineers working in the company’s German and French operations hadn’t used the same versions of the design software. When assembly line workers started installing bundles of wires, they discovered that the German software had miscalculated the amount of wiring needed for the fuselage, which had been designed on French software. Miles of wiring turned out to be too short and had to be torn out from half-completed airframes and replaced.
The A380 experience left Airbus with little appetite to develop another airplane from scratch. But after Boeing announced plans for the Dreamliner in 2004, the company was forced to respond. Carrying from 230 to 330 passengers, the Dreamliner would be a direct threat to Airbus’s highly successful A330 twin-aisle, which first flew in 1992. The company’s initial concept was to repurpose the A330 with more aerodynamic wings and more efficient engines. “Airbus was only just starting to see light at the end of the tunnel in the A380 saga, so naturally we were very risk-averse,” says Mike Bausor, marketing director for the A350.
The reconfigured A330 (which, confusingly, was also named the A350) was unveiled in 2004 and failed to attract many customers, who were unimpressed with the modest performance gains. “The market told us, ‘This is not what we want, we want a clean-sheet-of-paper design,’ ” says Bausor.
Instead of a cautious, incremental upgrade, Airbus went for an entire family of superefficient aircraft ranging from 276 to 369 seats, with a projected development cost of more than $10 billion. The goal was what Airbus internally calls “early maturity”—getting the program as quickly as possible to the kind of bugs-worked-out status that passenger jets typically achieve after years of service.
Airbus adopted standardized design software throughout the company to avoid errors such as the A380’s wiring miscalculation. It went further by creating a single electronic rendering of the airplane, called the digital mock-up, or DMU, that every engineer working on the airplane can use at any time. If anyone makes a change, everyone can see it.
As with any new plane, the early design phases were riddled with uncertainty. Would the materials be light enough and strong enough? Would the components perform as Airbus desired? Would parts fit together? Would it fly the way simulations predicted? To produce a working aircraft, Airbus had to systematically eliminate those risks using a process it calls a “testing pyramid.” The fat end of the pyramid represents the beginning, when everything is unknown. By testing materials, then components, then systems, then the aircraft as a whole, ever-greater levels of complexity can be tamed. “The idea is to answer the big questions early and the little questions later,” says Stefan Schaffrath, Airbus’s vice president for media relations.
In practical terms, this meant running all sorts of fabrication tests and creating demonstration units of major structures: afuselage barrel section in Toulouse; a wing-box demonstrator in Broughton, Wales; a landing-gear test rig in Filton, England; a cabin mock-up in Hamburg. Much of the early work was done not by Airbus but by its suppliers. While the company might look to the outside world like an aircraft manufacturer, it’s more of an integrator: It creates the overall plan of the plane, then outsources the design and manufacture of the parts, which are then fitted together. “We have 7,000 engineers working on the A350,” says Brégier, “and at least half of them are not Airbus employees.”
Throughout the development process, teams of engineers were brought in from suppliers to collaborate with Airbus counterparts in Toulouse in joint working groups called “plateaux.” “You need to have as much transparency with your suppliers as possible,” says Brégier. “With such a program you have plenty of problems every day, so it’s bloody difficult.”
A prime example of supplier collaboration can be found in Mexicali, Mexico, where Honeywell International has built a test facility called Air System Integration Bench (AirSIB). Here, Honeywell can study the interaction between the various subsystems it’s building for the A350, including the auxiliary power unit, the cabin pressurization system, and air conditioning. “Bringing it all together in Mexicali is a pure maturity play,” says Justin Ryan, head of Honeywell Aerospace’s Airbus business. “It makes for a cleaner test flight program.” During one flight, for example, engineers on the aircraft noticed a small glitch in the cabin pressurization system. “Instead of having to do more flight tests, we went to AirSIB and modeled it, saw that it behaved in just the way it had in flight, and figured out how to fix it,” says Ryan.
Near the tip of the system-testing pyramid is the “iron bird,” a full-scale skeletal airplane mock-up that Airbus has been operating in Toulouse since 2010. Pinned beneath an armature of scaffolding, the iron bird includes all the internal components of the actual airplane, including electrical and hydraulic systems, and is hooked up to flight simulators in the next room. It can model exactly what happens inside the pipes, tubes, and wires of the plane in flight. The idea is not just to put the systems through every combination of settings, but to see how the whole aircraft responds when individual parts are broken, overexerted, or misused. That, after all, is how the real world works. “Every plane in the air has something wrong with it,” Cousin says.
Also in Toulouse, a full-scale airframe is having one wing slowly bent upward by cables. In weeks to come, a hydraulic ram will rack the tail to one side. The goal of torturing the airframe is to make the structure just as strong as it needs to be and no more. “You don’t want to be carrying useless weight around with you on every flight,” explains Peter Boesch, head of A350’s static test program.
At testing facilities in Hamburg and Erding, Germany, sections of airframe are put through repeated deformations to create structural fatigue, the same way a paperclip bent back and forth will eventually break. This kind of damage caused the three doomed de Havilland Comets to come apart in flight; it’s been plaguing the A380, too. In 2011 and 2012, cracks were found within the superjumbo’s wings, prompting European authorities to order the entire fleet to undergo detailed inspection in case the condition led to “a reduction of the structural integrity of the aeroplane.” To minimize the chances of that occurring in the A350, the Erding facility is putting the airframe sections through more than 80,000 simulated takeoff and landing cycles.
In a sense, the real testing will begin only after the A350 wins certification. The first couple of years of service are when the biggest problems with an aircraft tend to emerge. It’s simple mathematics. Once the planes start flying in the dozens, the fleet as a whole will rack up flight hours at a rate hundreds of times faster than even the most aggressive test program. “They will accumulate a lot of experience and discover things that an aircraft manufacturer cannot,” says Brégier. This early period can be essential in establishing a new plane’s reputation. Conversely, a plane that’s proven reliable may not make the customers come running. Once the A380’s production problems were solved, it went on to enjoy an unusually trouble-free operational existence. But it’s found fewer buyers than Airbus anticipated and has yet to turn a profit for the company.
Company executives say the A350 is a safer bet. The A380 made its debut in a market that had never existed; the A350 will slide into a niche with a long history of robust demand. Airbus expects that over the next 20 years airlines will place almost 7,000 orders for planes with a capacity of 250 to 350 seats. At current prices, that’s about $2 trillion.
The A350 won’t have the market to itself. At the larger end, it will compete with Boeing’s recently announced 777X; at the smaller end, with the Dreamliner. So far, the A350 is doing well. By the end of 2013, Airbus had received 817 orders from 37 customers—more, in dollar value, than the Dreamliner had at an equivalent point in its development. Fueling optimism is the advent of Boeing’s rival 777X, which isn’t a clean-sheet design, but a ’90s-era aircraft outfitted with new wings and engines, the same kind of approach Airbus once tried to take with the A350.
In an L-shaped hangar across the ramp from du Ché’s office, a single airframe sits with its tail to the door in the 100-foot-high space. The last of the test airplanes, MSN005, has just received its wings and awaits its engines. Workers stride across the floor or climb within the yellow boxlike scaffolding that flanks the plane’s midsection.
Airbus will build aircraft here when the testing is done. As the process gets closer to the point of the pyramid, materials are formed into devices, devices are linked into subsystems, and subsystems are packaged into systems. Things that might work perfectly fine on their own may create problems when called on to function together. The goal during the entire process is to get rid of these bugs as early as possible, so at the end all that remain are problems of the highest level of emergence. At the pointy end of the pyramid lies “the final integrator,” as du Ché puts it: the aircraft.There will always be surprises when real wings and fuselage are sent up into real air. Early in Airbus’s test flight program, for instance, engineers riding in the midsection of the A350 noticed a buzzing sound during certain phases of flight. Repeated attempts to discern the cause came up empty. Finally an engineer suggested that a flexible seal in the wing be replaced with sturdier material. Sure enough, the noise went away.
MSN001 and its newer sister aircraft, MSN003, have logged about 1,000 hours of a planned 2,500-hour test program. Over the next four months, three more planes will join the test fleet, and the regimen will expand to include cabin entertainment systems, avionics, and the airplane’s performance in extreme temperatures. The A350 test flight program so far has uncovered half as many problems as the A380’s did—evidence, du Ché says, that Airbus’s debugging strategy is working.
Although the highest-risk parts of the test flight program were largely ticked off during the first few months of flying, one crucial test has had to wait because of the vagaries of the weather. And so one unseasonably mild day in early winter, du Ché finds himself looking out his office window at the blue sky with a touch of exasperation. A large high-pressure system hangs over Europe, preventing the kind of thunderstorm du Ché requires to conduct the so-called natural icing test. The idea is to fly into the edge of a storm, allow ice to build up on the wings and other surfaces, and see how the plane reacts to the added weight and loss of aerodynamic efficiency. The test fits du Ché’s personal definition of interesting.
“It’s uncomfortable,” he says. “And you are very likely to damage the aircraft, because you can have many, many lightning strikes.” Naturally, he’s impatient to get up there.
— With assistance by Carol Matlack
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