Airbus' casting commotion: as the largest commercial airplane ever built, the Airbus A380 is expected to take passengers longer distances with better fuel economies. Key ingredients in this aircraft's success are engineered cast components.

When the concept of the Concorde jet fascinated those in the aerospace industry in the 1960s, it was slated to be the future way to fly. Via the high-speed airplanes traveling at Mach 1, a passenger could travel around the world in one day, maybe twice. However, excessive operational costs, expensive ticket prices and limited fly space grounded such planes in 2003, leaving the torch to be passed on to another aircraft for innovative transport. Airbus decided to take control.

The France-based aircraft manufacturer had been producing commercial airplanes for more than 30 years, but its newest endeavor was to create the largest commercial airplane to date. On Jan. 18, Airbus unveiled the first completed A380 at its headquarters in Toulouse, France. Thousands were on hand to witness the spectacle, thus paralleling the first unveiling of the Concorde, Dec. 11, 1967, also in Toulouse.

The A380 will transport more than 500 passengers up to 8,000 nautical miles, and its cargo model, A380F, will carry up to 330,000 lbs. for 5,600 nautical miles. This is a step up from the firm's A340-600, which can carry 380 passengers for 7,900 nautical miles. The A380s include two full-passenger levels, and both models have four engines. Yet, they will be more fuel-efficient than any preceding trans-continental aircraft.

To maintain this weight and energy in the air for such a prolonged period of time requires stability from the components throughout the aircrafts' engines and structure. With the help of Alcoa Howmet Castings, Cleveland, the A380s will arrive as one of the most progressive vehicles in the commercial aerospace industry. Airbus expects to build multiple versions of the A380s, and most will fly with cast engine airfoil components and cast hydraulic vessels produced by Howmet.

Getting The Call

The idea of the A380 was not something that was spawned after the fall of the Concorde enterprise. In fact, Airbus had been considering such a vehicle for more than 10 years and officially began development within the last five. Upon aircraft design, two companies were commissioned to construct the engines: Rolls Royce, Derby, England, which produced previous Airbus engines; and the Engine Alliance, East Hartford, Conn., a joint venture between General Electric (GE) and Pratt & Whitney, with assistance from MTU Friedrichshafen GmbH, Friedrichshafen, Germany. But these companies needed assistance in creating internal components for the engines.

Howmet's Whitehall, Mich., investment casting facility specializes in engine airfoil castings, recently assisting GE and also helping break aircraft engine thrust records. The plant also has cast components for past Airbus programs and currently maintains a long-term agreement to cast airfoils for other Rolls Royce engines.

With this reputation, the Whitehall plant got the nod to produce 65% of the airfoils for the Engine Alliance GP7000-series engines and 35% of the airfoils for Rolls Royce's Trent 900-series. Even though another metalcasting firm cast the components for the A380 unveiled in January, Howmet will take part in the high-volume production. "It's a very competitive environment, and we do all we can to have the best combination of technology and service and be cost-competitive," said Howmet's Manager of Marketing Promotions and Communication, Tim Kinney. "That's the value package. The more success you have doing (the previous) programs, the better chances you have for the next go-around."

Howmet has a smaller share with Rolls Royce because the engine company employs a metalcasting facility of its own where airfoils are cast. However, Howmet actually may cast more airfoils for that firm than the Engine Alliance. "Even though there's a smaller market share on the Trent, Howmet actually might end up producing more airfoils for Trent just because they might have sold more engines," said Kinney. "It depends on the volume of purchases."

Howmet will cast its airfoils using single-crystal casting methods, which provide for a no-boundary, single-grain structure throughout the casting. Two kinds of airfoils will be cast: turbine blades (which rotate) and turbine vanes (which are stationary).

These nickel-based superalloy gravity-poured components require placement at the rear (turbine) sections of the engines where the air is compressed at 700 lbs./sq, in., thus causing temperatures to exceed the melting points of the airfoil alloys. In fact, temperatures in the engine core can reach up to half those on the surface of the sun, 5,000-6,000F (2,760-3,315C). The airfoils, therefore, are coated to prevent any corrosion during operation. Although Rolls Royce likely will apply its own coatings at its facility, Howmet is applying a platinum aluminide solution to the GP7000 airfoils.

Despite the heat, the airfoils maintain a cool enough temperature in the engine because of their excessive rotation and also the internal passageways, which are cast-in features on each component. These passageways allow air to pass through the part when in use, thus cooling it even more. The passageways also are coated with the same platinum aluminide material, and though they are not 100% solid internally, they maintain their structure thanks to the single-crystal properties.

Once the airfoils are complete, they will be sent to various plants of each engine company for additional machining, testing and assembly.

Under Pressure

More than 500 Howmet airfoils will be installed in the back of each engine. The airfoil blades vary from 2-12 in. (5.08-30.5 cm) in length depending on their engine stage. Generally, aerospace combustion engines have several pressure stages in their turbine areas.

The commercial GP7270 and cargo GP7277 are designed with two stages of high-pressure airfoils and six low-pressure airfoils. The commercial Trent 970 and freight Trent 977 incorporate three stages of airfoils--one high-pressure, one intermediate-pressure and five low-pressure. For each stage of rotating blades, there is a stage of vanes bolted together forming a circle adjacent to the blades.

Most people are familiar with just the fan that is exposed at the front of aerospace engines. But after the air passes through the large fan, it is exposed to a series of blades that compress the air and push it into the combustor, where it is mixed with fuel and explodes, thus increasing its temperature.

From there the air is forced into the turbine area at a very high pressure and hits the first stage of vanes. The vanes then turn the air so it efficiently makes contact with the blades, which will then rotate like a household fan but with much more intensity. For instance, the high-pressure blades in the Trent 900 engines can produce more horsepower than a Formula One race car.

After the high-pressure stages, the air passes through the immediate-pressure stage (for the Trent), the low-pressure stages and out the engine. The rotation of these pressure stages, in turn, assists in the rotation of the engines' compressor and fan sections. When in full operation, the A380 passenger engines will produce 70,000 lbs. of thrust, and the freight A380F will use engines operating in the 76,000-77,000 lbs. of thrust range.

Much to Endure

To achieve such energy, Howmet's A380 airfoils undergo a series of tests to ensure they meet the standards for the groundbreaking aircraft.

Howmet took part in several concurrent engineering processes with the engine companies to accelerate the project. The facility rapid prototyped an initial set of parts and sent them to the engine makers in 2004, where they were assembled on a test engine. According to Don Larsen, account manager for Pratt & Whitney, the engine was examined to see if it met its fuel efficiency, noise standards and other advertised benefits. "There's a whole myriad of tests that they go through before they ever make it on a wing," he said. "(After these tests), the engines go through endurance testing, where they run it for an extended period of time to determine if components are lasting as long as they could or should."

Howmet's airfoils sustained the trial tests, and once the design was approved, the firm began to cast the airfoils on a high-production basis. Kinney noted how rapid prototyping saved the customers in expenses. "The benefit was we didn't have to invest all that money into hard tooling that you would have to reinvest for a slight design change," he said. "Once you have the design set, and you shift hard tooling for production, you don't want to change your tooling."

Wing Zone

In addition to the blades and vanes, Howmet is casting hydraulic vessels and their lids for the A380s. These components, being produced at the company's Laval, Quebec, Canada, casting facility, are subcontracted through CESA, Getafe, Spain, and will be embedded in the outer engine pylons of each A380 wing to contain the hydraulic oil. The design of these vessels is slightly different than the previous welded designs on other Airbus planes.

Because the A380 required a more spherical shape to fit into a contoured space in the wing, the company knew it needed a solid casting to obtain the proper form and fit. The casting required both thick- and thin-walled sections and demanded a high strength level while retaining a light weight.

Howmet was the only metalcasting firm that proposed the idea of a one-piece vessel casting that could meet the requirements, as opposed to other companies that examined two-part designs. The Laval facility incorporated rapid prototyping conversion methods to achieve the single-piece shape, created tooling capabilities for the components and even made some production-level castings.

However, CESA soon changed the vessel design from 31 in. (78.7 cm) to 28 in. (71.1 cm) in diameter when it was determined that not as much hydraulic oil was needed. This forced Howmet to develop a new set of die tooling for high production, which led to additional expenses. Nevertheless, the tooling now is complete, and Howmet Laval is investment casting the A356 aluminum alloy vessels and shipping them to CESA's plant in Getafe. From there, the parts will be incorporated in each A380 wing and sent to France for the final assembly of the aircraft.

Ready to Taxi

With this new project to tackle, significant employment increases are expected for all firms involved. According to Kinney, the Whitehall facility will increase employment by 80 full-time jobs when production is at full-scale. Further, Allan C. McArtor, chairman of Airbus North America, noted that 50% of the components and subsystems for the A380s will be produced in the U.S., thus increasing job production for other domestic firms. The A380 program may generate a 30-year increase in job creation, with numbers nearing 23,000 in 50 years. "While out-sourcing is an issue for so many today, Airbus is delighted to be among those companies who are 'insourcing' high-technology jobs," McArtor said. "In the aerospace business, the supplier delivers a solution. The predictability and lifecycle performance are the most significant aspects. We can't have cheap parts that fail."

At the moment, the supplier companies and Airbus are progressing in completing the A380s to fill testing and contract requirements. The aircraft will use Trent 900 engines on its maiden voyage in the spring of 2006 with Singapore Airlines. More than 10 commercial/freight companies worldwide have submitted orders for at least 130 planes, and more are in close prospect. Four test A380s now are complete and the first A380 to fly has finished many of its ground and systems tests.

It cannot be stated that the torch has officially been passed, but Airbus Communications Manager Mary Anne Greczyn attributed the outlook on the A380 to the dedication of all firms involved. "We could not have developed the A380 to be the aircraft of the future without the cooperation and technological research and development of our supplier companies, including American suppliers like Howmet," she said. "This is a team plane from the get-go."