Meeting the production ramp-up challenge

Pratt & Whitney’s PurePower Geared Turbofan (GTF) engine will start making its entry into service on the wings of Airbus A320neo and Bombardier CS100 jetliners. The challenges of putting a new commercial aero engine into production can be daunting, especially with 7,000 orders and commitments. To speed the pace of delivery, the company developed overhead-automated horizontal moving assembly lines for the GTF jet engines for its facilities in Middletown, Connecticut; West Palm Beach, Florida; and Mirabel, Québec, Canada, as part of a $1 billion facilities investment.

The lines integrate manufacturing data and optimal ergonomics to allow technicians to assemble up to 500 engines per year. Meeting that production rate requires a well-choreographed supply chain coupled with a highly developed manufacturing process.

Produceability is key

P&W’s Vice President of Engineering Tom Prete, must ensure the GTF engine transitions smoothly from the development phase through the ramp-up to full production.

The GTF has been a successful seller on multiple platforms, requiring a far-sighted approach to be ready for the large number of engines that Pratt & Whitney will need to produce. Prete is confident the company is prepared for the ramp-up. 

“We’ve been working multiple strategies with the procurement and operations sides of the business to ensure a robust supply chain with multiple sources so there’s no single point of failure,” Prete says. The company now has more than $22 billion in long-term agreements with suppliers.

“Our engineering design people work with manufacturers to focus on produceability – the critical features and attributes of the parts from a design perspective – to ensure that the process control is in place during the ramp-up,” Prete says. “Having designers work in parallel before the ramp-up helps ensure process capability meets technical requirements. Then it’s working with suppliers so parts are produced well and to the requirements out of the gate.”

Automation is critical to making the ramp-up successful, and is used to remove variation from processes.

Prete notes, “Where blending or polishing is required – things traditionally done by human touch – we’ve been focused on advanced automation to do those operations. That’s been a benefit both in terms of touch-time labor reductions, but also repetitive motion injuries have been greatly reduced.”

Design for reliability

“There’s no doubt that the engines we design today are a lot more complex than previous engines,” Prete states. “Part of the design process has been to optimize for reliability.”

While the GTF design is optimized for performance, weight, and technical metrics, it’s also optimized for cost and manufacturability.

“We have integrated product development teams that get input from all the stakeholders in the engine. When we’re done with the design it not only meets all of its technical requirements, but it has to be reliable and be produceable,” Prete explains.

Modularity for maintainability

The GTF engine benefits from an integrated product design. According to Prete, both design and manufacturing engineers participate from the beginning in designing parts and modules. Input from the aftermarket stakeholders also ensures the designs are not only manufacturable, but also maintainable on the flight line.

Materials & machinability

Even though they are considered new processes, powder-metal additive manufacturing for compressor stators and synch ring brackets, single-crystal alloy turbine blades, aluminum-lithium alloys, and ceramic thermal barrier coatings were mature technologies when they were incorporated into the GTF’s design. Prete notes the availability of these new materials offers the opportunity to re-examine a design constraint or increase the capability of the engine.

One example of how materials can influence design is the GTF’s use of hybrid metallic fan blades. Since the engine’s planetary gear system permits the fan to run at lower speeds, the stresses are lower, allowing P&W engineers to consider innovative materials. A hybrid metallic fan blade based on aluminum-lithium alloys enabled engineers to put discrete aerodynamic features into the design for better efficiency.

“We did not have to make the trade-offs that we have to make with a composite resin solution where you can only get certain types of radius on trailing and leading edges,” Prete explains. “Going to a metallic fan blade allows us to put in features that are the most aerodynamically friendly. It’s one of the reasons we achieve 16% fuel efficiency gain with the GTF.”

As part of the development of new materials, P&W engineers do machinability trials and compare them to existing alloys. Prete says this process involves a number of Tier 1 CNC machine manufacturers that can bring new technologies to bear.

The engineers take the results of the tests and back-feed them into current methods of machining and processing the parts in current production engines.

Data from engines

Big Data will improve engine monitoring from the field and inform future design.

“We get data from the engines that gets fed back into engineering, and we can see how the parts that we designed, developed, and saw through certification are working,” Prete remarks.

It will close the feedback loop between design process and how engines perform in service, according to Prete.

“We’re excited about Big Data’s role in engineering next-generation engines, ensuring we can make upgrades to engines in the field now,” Prete concludes.

Pratt & Whitney

www.pw.utc.com

About the author: Eric Brothers is senior editor of Aerospace Manufacturing and Designand can be reached at ebrothers@gie.net or 216.393.0228.