One-third of GE’s Catalyst engine, a turboprop set to fly in the Cessna Denali, is 3D printed. It has the most 3D-printed parts of any plane engine in the world. (Credit: GE Aviation)

In 2014, eight engineers started a secret project behind the walls of GE Aviation’s headquarters. Their challenge? Build an aircraft engine with 3D printing instead of traditional manufacturing.

The engineers wanted to make an engine with fewer parts than normal – way fewer parts. The normal CT7 turboprop –