The concept of printing metallic parts for aerospace applications in place of traditional forging and casting may be in its infancy, but General Electric says the coming revolution in additive manufacturing for aircraft engines is approaching quickly and on an unprecedented scale.

“It is the breakthrough we have been waiting for,” says GE Additive vice president Mohammed Ehiteshami. “In engineering we always do a trade between weight, cost and efficiency, but additive manufacturing gives you all three at the same time.” Describing his first exposure to the new technology, he adds “the first time I saw it I couldn’t go home. I said ‘oh my god, all these 30 years of anxiety over whether I want to make it heavier or stronger, it all can go away!’”

Revealing the extent of GE’s additive manufacturing plan, GE Aviation Business vice president Brad Mottier says “we have spent about $1 billion to develop this.” Although printed parts are already in service on the CFM Leap engine, the first large scale application will be the company’s clean-sheet-design Advanced Turboprop (ATP), which will power the all-new Cessna Denali single-engine turboprop aircraft. Additive parts will cut the ATP’s weight by 5% while contributing a 1% improvement in specific fuel consumption.

To validate the parts GE has also revealed that in a secretive ‘Skunk Works’ style project, it is testing a 35%-additive manufactured demonstrator engine.  Dubbed the ‘a-CT7’, a reverse engineered CT7-2E1 technology demonstrator was designed, built and tested in 18 months. The process reduced more than 900 conventionally made parts to just 16 additive manufactured parts.

The demonstrator was based on the venerable turboprop because the ATP engine architecture is derived from the CT7.  “It includes three frames, eliminating 100s of parts in each, and a simplified bill of materials. As we played with this we realized we could reduce the weight and cost by 30-35% and that we can also open the design space,” says Ehiteshami.

As a result the ATP, which will run for the first time by the end of 2017, will utilize more additive parts than any production engine in aviation history says GE. Some 855 normally made parts will be reduced to just 12 additive parts including sumps, bearing housings, frames, exhaust case, combustor liner, heat exchangers and stationary flowpath components. Although production ATPs will be built in Prague, Czech Republic, GE has yet to decide where the parts will printed.