The boot camp for some of the world’s most advanced jet engines is hiding deep in the foothills of the Appalachian Mountains in rural southern Ohio. The Peebles Test Operation, named after the largest small town nearby, Peebles, population 1,728, is where GE subjects its engines to groaning trials that involve hail and ice blasts, hurricane-force winds, bird strikes and other extreme hardships that exceed anything they are likely to encounter in service. The tests reflect the stringent requirements the U.S. Federal Aviation Administration and other regulatory agencies impose on jet engines before they are certified for commercial service.
One of the strangest structures at the 7,000-acre facility is a grey honeycombed orb spanning 32 feet in diameter. Walk closer and the mysterious sphere appears like a translucent alien beehive stuck the front of a jet engine. It is made from an array of 300 flat aluminum honeycombs and perforated stainless steel plate panels of varying sizes, and weighs 30,000 pounds.
This is the “turbulence control structure,” TCS for short, and GE owns three of them. The orb is really a high-tech wind shelter. Its purpose is to smooth out the flow of air into a jet engine that is being tested. This is helpful during simulations of engine distress including variations in fuel flow and “deterioration” of the engine compressor and turbine. Engineers also use it to reduce variation in thrust and fuel consumption data. “You take wind-induced inlet airflow variation out of the picture,” says aerospace engineer Jose Gonsalez from GE Aviation. “You don’t want that as a variable when you collect performance data across many days under different conditions.”
Gonsalez, who came to GE from NASA, has been testing jet engines at Peebles for seven years. He says that the TCS dome makes the test site more efficient. The dome was first introduced in the 1990s, when GE started testing its largest engine, the GE90. “Before the TCS, you would have to wait for calm conditions to be within your wind envelope, typically from dusk through early morning,” Gonsalez says. “Now when there is a lot of sunshine and convective heating from the sun, you can better deal with the variable wind conditions caused by them and expand your allowable wind envelope. We can run more tests more often.”