Score one for the humans. After four years of trial and error, Boeing Co. is dumping the robots that build two main fuselage sections for its 777 jetliners and the upgraded model known as 777X.

Instead, the Chicago-based planemaker will rely on skilled mechanics to manually insert fasteners into holes drilled along the circumference of the airplane by an automated system known as “flex tracks,” which it developed and honed on the 787 Dreamliner.

The shift to the new human-plus-machine system began during the second quarter and should be complete by year’s end, Boeing spokesman Paul Bergman said in a statement. Boeing doesn’t plan any change in total staffing for its 777 jetliners, which are manufactured in Everett, Washington, about an hour north of Seattle.

“The flex track solution has proven more reliable, requiring less work by hand and less rework, than what the robots were capable of,” he said.

As tempting as automation can be — with its promise of a mechanized workforce that never gets sick, tired or hungry — manufacturers are finding many cases where the technology hasn’t yet caught up to the dexterity and precision of human hands and eyes. Tesla Inc. famously tried to build a fully automated car factory in Fremont, California, before adding a tent outside of the facility to allow more work to be done by hand.

Boeing’s fully automated initiative — known as FAUB, for fuselage automated upright build — relied on robots working in tandem to drill holes precisely and fasten together metal panels held upright to create the outer frame of the hulking twin-engine jets. It was showcased as part of the advanced manufacturing that Boeing is pioneering on the 777X, and that it plans to expand to future jetliner programs next decade.

Out of Sync

But the planemaker struggled to keep the robots moving in sync on the outside and inside of the fuselage panels, creating production snarls when it first introduced the FAUB technology to the legacy 777 line. A Seattle Times report from 2016 described a swell of worker overtime and incomplete jobs that were finished after jets rolled out of the factory.

“It was hard. It took years off my life,” Jason Clark, a Boeing vice president overseeing 777X production, said during an interview earlier this year.

The robot flub isn’t a complete loss. Boeing learned some valuable lessons from its “first very deep dive into that type of technology,” Clark said. “It’s taught us how to design for automation.”

The new flex-track method creates less wear-and-tear on workers since machines handle one of the the most physically demanding tasks of the fuselage assembly: drilling holes through metal.

Also, “We redesigned portions of the build to replace rivets with less difficult forms of fasteners, further improving the ergonomics,” Bergman said. The combination should bring improvements in safety, quality and factory flow, he said.

The 777X will be Boeing’s largest-ever jetliner, but the plane isn’t expected to take its first flight until next year after General Electric Co. unearthed a durability issue with its GE9X engines. The company relies heavily on robots to manufacture the plane, from wings spun from resin-infused tape to self-guided vehicles used to transport large components within the factory.