Tucked into the foothills of the Appalachian Mountains in a rural corner of southern Ohio, GE Aviation’s Peebles Test Operation, a 7,000-acre engine test complex has always been surrounded by thick woods, as well as an air of mystery.
The Peebles complex, named after the nearby village, operates 11 large jet engine test cells — including two massive indoor test facilities — as well as engine assembly and repair buildings spread over an area more than eight times the size of New York’s Central Park. More than 300 people work around the clock at Peebles, where they take new commercial and military development engines through a battery of ground tests to make sure they keep working when they fly into a hailstorm or encounter a dust cloud. The workers also run final acceptance tests on all production engines before they are delivered to customers, and perform final engine assembly for the record-breaking GE90 and GEnx commercial engines powering Boeing’s 777 and 787 Dreamliner jets, as well as the Passport business jet engine. Simply put, with GE Aviation’s record engine backlog, the Peebles operation is the backbone for the largest commercial jet engine production run in aviation history.
And yet, at the same time, the secured Peebles site has always been something of an enigma. Area farmers hear the engines roar from afar but can’t see them. Over the years, reporters have questioned whether GE hosted covert operations from its hilltops in the mountains. Even wilder, a national science fiction program on cable TV in the 1990s demanded confirmation from GE Aviation headquarters in Evendale some two hours away that UFOs had landed at the Peebles site at night.
What’s with that? Well, you have to go to the beginning.
Top: GE’s GE9X jet engine at an outdoor test stand in Peebles. The engine will power Boeing’s new 777X jets. Above: An engineer stands by a huge air inlet into a indoor test cell. Engines like the GE90-115B, the world’s second most powerful jet engine after the GE9X, can swallow as much as 8,000 pounds of air per second. Images credit: Chris New for GE Reports.
In 1948, at the height of the Cold War, GE Aviation established a military engine assembly operation in Evendale, a Cincinnati suburb. Six years later, the company began quietly purchasing thousands of acres 80 miles away in remote Adams County, Ohio. As rumors mounted, GE held a town meeting in Peebles to deliver the news: The company had purchased up to 5,000 acres in an isolated valley surrounded by 300-foot ridges to create an outdoor test facility for top-secret military engines.
Under a page-one headline from The Cincinnati Enquirer, “Pogo Tests in Adams Area!”, the facility was described as “one of the most carefully guarded industrial deals ever to take place in this area.” GE disclosed plans to test military engines for vertical takeoff aircraft (nicknamed “pogo stick planes” at the time) and military engines with thrust reversers. The tests required outdoor sites not confined by walls.
A giant orb called the turbulence control structure is really a high-tech wind shelter. It helps crews smooth out the flow of air into a jet engine during simulations of engine distress, including changes in fuel flow and “deterioration” of the engine compressor and turbine. Image credit: Chris New for GE Reports.
In 1955, GE formally opened “The Proving Ground,” as it was called for decades, and ran tests on an outdoor platform with performance data recorded nearby in a former farmhouse. GE tested jet engines, including GE’s first supersonic jet engine, the famous J79 fighter jet engine, as well as rocket engines.
The facility’s first manager, Robert D. Knies, described his duties as “soil conservationist, forester, tobacco farmer, instructor of voluntary fire departments, house wrecker, horse buyer, and game warden.” Acres of tobacco grown on the property helped GE to finance the site’s conservation projects. Area farmers removed abandoned houses on the property in exchange for the lumber. Paths were cut into the forestland to provide access for a GE-trained, volunteer fire department. Guards patrolled the 5,000 rolling acres on horseback.
Air inlets into indoor test cells. Image credit: Chris New for GE Reports.
All of this simply added to the mystique. In 1958, The Associated Press ran a national news item regarding “dense smoke sighted” near the test operation. What could it be? “Officials refuse to disclose,” the article concluded. Well, there you go.
By then, more test sites had been built, along with a 3,000-foot runway strip to handle landings by small aircraft from Cincinnati. Six ponds with a storage capacity of 10 million gallons of water were eventually established. That’s because during the water ingestion test, for example, Peebles employees blast 800 gallons of water per minute inside a GEnx engine running at full thrust. The U.S. Federal Aviation Administration and other regulators require engine makers to run jet engines through this one and dozens of other trials before they are certified to fly. The latest engine to face this grueling rigmarole was the GE9X, the world’s largest and most power jet engine.
But all this was still in the future. In the early 1960s, the site was nearly mothballed as GE’s military engine development activities slowed. The company had yet to become a leading engine producer for commercial jetliners. Wisely, it maintained ownership of the vast property.
A LEAP engine at an outdoor test stand in Peebles. Image credit: CFM International.
In 1966, the Peebles operation began testing GE’s all-important TF39 high-bypass turbofan engine for the U.S. Air Force’s C-5 Galaxy. From the TF39 technology, GE would establish the wildly successful CF6 family of commercial engines. By the early 1980s, the fast-selling CFM56 engines from CFM International, a 50-50 joint venture between GE and Safran Aircraft Engines of France, were being tested in the Ohio hills along with several new military engine programs, including the F110 for the F-16 fighter jet.
As GE Aviation has grown, the Peebles operation has grown right along with it. By 2008, GE’s rising production and development work required a $90 million expansion at Peebles. Before long, GEnx and GE90 fan cases and composite fan blades were shipped to Peebles to be attached to engine propulsors — compressor, combustor, and turbine modules assembled together — from GE Aviation’s factory in Durham, North Carolina. Six years later, GE completed another $70 million expansion at Peebles, bringing the number of indoor and outdoor test cells to 11.
Jet engine test cells have 20-foot-thick walls built from a special high-density concrete. The construction team vibrated the wet concrete down to squeeze out air and eliminate weak spots. Image credit: Chris New for GE Reports.
Over the years, the Peebles operation has hosted Ohio governors, U.S. Congressional leaders, as well as military and airline industry leaders. TV news programs around the world have profiled the operation. GE executives will privately tell you they love to visit Peebles simply “to get their aviation batteries recharged.” Also, the Peebles site has long been a critical part of the Adams County economy.
The Peebles operation has come a long way from the days when security officers patrolled the grounds by horseback. But given its size and secluded location, not to mention the advanced military engines quietly transported there, the operation still maintains a distinctive aura.
Over the years, reporters have questioned whether GE hosted covert operations from its hilltops in the mountains. Even wilder, a national science fiction program on cable TV in the 1990s demanded confirmation from GE Aviation headquarters in Evendale some two hours away that UFOs had landed at the Peebles site at night. Image credit: GE Aviation.
A version of this story originally appeared on GE Aviation’s blog.