Moss and his team developed what they called a turbosupercharger. Back then, any forced induction device was called a supercharger, so this turbosupercharger was a supercharger that used exhaust gases to spin a turbine, which then powered the air compressor to increase the explosive charge. Today, of course, people typically just drop the “super” and call this a turbocharger, and only refer to it as a supercharger if the compressor’s mechanically driven, such as by belt, chain or gear.
In May 1918, this top-secret innovation arrived at a U.S. Army Air Service facility in Dayton, Ohio. The military’s recently founded air wing had set up shop in the same place where the Wright brothers grew up and designed their first aircraft, and this new test was meant to quite literally push the envelope yet again.
(Quick side story. The turbocharger was being tested on a Liberty engine, which honestly deserves its own article, but here’s the short version. A month after the U.S. declared war on Germany, the military called on two leading engine designers from Packard Motor Car Company and Hall-Scott Motor Co. to whip together a new American aircraft engine. The government then contracted out the manufacturing to several automotive manufacturers. When General Motors founder and pacifist William Durant initially refused to produce the engines, Henry Leland, who originally founded Cadillac, left GM to form another company, which at first strictly produced thousands of Liberty engines thanks to a hefty contract. Leland called the new firm Lincoln Motor Company, after Abraham Lincoln, the first president he voted for. It was only after the war that they converted their manufacturing facilities to produce luxury cars.)
Anyway, the brand new engine and its brand new turbo performed reasonably well in initial testing, albeit the additional heat generated from the additional pressure kept melting spark plugs and other components. This was one of the reasons earlier forced induction tests failed, because the materials available couldn’t stand up to the extreme temperatures. Fortunately, they now had the resources available to solve for those challenges.
However, the real test was going to be how it performed at altitude. Dayton’s only a few hundred feet above sea level. The military had previously tested the Liberty atop Pikes Peak – the highest mountain that’s closest to Dayton, which also happens to have a road all the way to the top – so they now arranged another trip to test the blower-equipped version.
In Ohio, the unassisted Liberty produced 350 horsepower. On the 14,000-foot summit, it produced 230 horsepower, or a third less. With the turbo attached at altitude, it produced 356 horsepower – more power than the turbo-less engine did near sea level.
The test was a success, but very shortly afterward, the Allies won and WWI ended. The work had no impact on the war, but it showed tremendous promise. Turbos soon ushered in the era of high-altitude flight, raising planes’ ceiling so they could fly above bad weather at high speeds. With this distinguished legacy, Moss retired in 1938 as the founding father of GE Aviation, and some say the turbo itself.