How Sanford Moss’s Turbosupercharger Saved GE’s Fledging Aviation Business

The father of GE Aviation was a diminutive, nervous, and idiosyncratic inventor with round spectacles and a Van Dyke goatee. His colleagues at GE’s factory in Lynn, Massachusetts, thought he was brilliant. And a bit peculiar.

Dr. Sanford Moss carried pockets of quarters to engage coworkers in coin-matching contests to prove the laws of probability. He claimed that true mechanical engineers wanted to disassemble their pocket watches to understand the inner workings. In 1938, Mechanical Engineering magazine described Dr. Moss as possessing “that disarming characteristic of small boys with whom it’s impossible to be angry for long in spite of a somewhat exasperating behavior.”

More ironic, this early aviation pioneer hated to fly in airplanes. He took occasional commercial flights when necessary, but refused to be a passenger in experimental military aircraft, which even featured his own technology.

And yet, just over 100 years ago, Dr. Moss almost singlehandedly gave GE its critical toehold into the new, fast-evolving aviation industry when he led the design of the first practical “turbosupercharger,” which allowed piston-powered airplanes to soar at record heights.

 

Dr. Moss led the design of the first practical “turbosupercharger,” which allowed piston-powered airplanes to soar at record heights.

The turbosupercharger had a centrifugal compressor (impeller) attached by a shaft to a turbine wheel. The piston engine’s hot exhaust gas was directed into the device’s turbine, thereby turning the compressor. Its fast-rotating impeller squeezed the thin air fed into the compressor, thus creating a higher air density and oxygen level closer to sea-level pressure. The “turbosupercharged” air was fed into the piston engine’s carburetor, allowing the airplane to fly at high altitudes despite the thin air.

The GE design introduced several innovations, including passages for critical cooling air to the turbine wheel. Dr. Moss liked to say the device “kidded the piston engine to think it was at sea level.”

During 1919-1921, newspaper headlines across the world heralded the record-altitude flights – surpassing 40,000 feet – by U.S. military aircraft from Dayton, Ohio, using piston engines boosted by the “innovative and secretive” GE turbosupercharger.

The excitement climaxed in July 1921 when Army General Billy Mitchell dropped bombs at 15,000 feet from a military bomber boosted by the GE device, and sunk two target battleships. It foretold a future era in aerial warfare.

However, Dr. Moss did more than create GE’s fledging aviation business. He saved it. Without his stubborn vision, the company’s foray into aviation could have easily ended in the mid-1920s when interest in high-altitude flying waned. Despite all of the earlier publicity, no major production contracts for the GE turbosupercharger materialized. Dr. Moss held together a small engineering team at the Lynn operation by supplying components for internal superchargers for piston engines produced by Pratt & Whitney and Wright Aeronautical.

On more than one occasion, Dr. Moss experienced what he called the “glassy eye” from GE executives who questioned the validity of the GE turbosupercharger and its future potential.

When Everything Changed

Then, everything changed. As the world became unstable in the late 1930s, Boeing introduced its four-engine B-17 bomber, which used four GE turbosuperchargers. High-altitude bombing capability for the Allied nations became increasingly important as Nazi Germany invaded Europe. That year, the U.S. Army Air Corps called for GE to produce 230 turbosuperchargers to enable a 1,000-horsepower piston engine to maintain full power to 25,000 feet.

That contract took GE out of the realm of limited “experimental” work and gave rise to the creation of the GE Supercharger Department in Lynn. Even though Dr. Moss retired in 1938 at age 65, he was soon back and in the thick of it as technical advisor. Production soared. After the U.S. entered World War II in December 1941, GE began producing turbosuperchargers in four U.S. locations. By 1943, more than 100,000 GE turbosuperchargers powered U.S. and Allied aircraft.

 

GE engineer Sanford Moss (right) built the company's first turbosupercharger by tweaking a design for a gas turbine. Here he shows the device to James H. Doolittle, the Air Force commander who led the "Doolittle Raid" on Japan four months after the attack on Pearl Harbor. Image credit: Museum of Innovation and Science Schenectady.

The GE role in the war effort made the elderly Dr. Moss a media celebrity. In 1941, he received the prestigious Collier Trophy for technology that enabled Allied bombers to operate at high altitudes. Newspapers and magazines profiled the eccentric GE inventor, who, as a teenager in the late 19^th century, worked for $6 a week in a dusty machine shop in San Francisco, California, and became fascinated by motors and air compressors.

That modest job influenced his decision to earn degrees in mechanical engineering from the University of California. In 1903, he received a doctorate from Cornell University in Ithaca, New York, with a thesis on gas turbine technology. In the school laboratory, he was among the first Americans to power a turbine with combustor gas by burning fuel in a chamber under pressure to operate a turbine.

Upon graduation, Dr. Moss joined GE’s growing Steam Turbine Department in Lynn. He collaborated with legendary GE technologists Elihu Thompson and Charles P. Steinmetz. GE allowed Moss to experiment with his gas turbine concepts. However, without high-temperature metals and efficient compressors and turbines, his early gas turbine designs were not commercially viable. Nevertheless, his centrifugal compressors influenced future industrial applications.

After the U.S. entered World War I in 1917, the U.S. government engaged GE and Dr. Moss to pursue turbosuperchargers for Allied airplanes. Dr. Moss and his team successfully demonstrated the GE device in late 1918 atop Pikes Peak. It boosted a Liberty engine to reach 356 horsepower at high altitude, compared to 230 horsepower without it. The following year at McCook Field in Dayton, Army Major “Shorty” Schroeder climbed into the open cockpit of a French-designed, Packard-built Lepère biplane for the maiden flight of GE’s turbosupercharger. It was attached to the forward end of a U.S.-designed Liberty engine.  The impact was immediate.

 

Dr. Moss in 1903.

Fast forward 20 years, and Dr. Moss’s continued devotion to the turbosupercharger not only firmly established GE as a wartime aviation company, but also positioned the Lynn operation to be selected by the U.S. Army Air Corps in 1941 to develop America’s first jet engine using the design of British inventor and military pilot Frank Whittle.

GE was the logical selection because of its innovative impellers, turbines, turbosuperchargers, and compressors – technologies influenced by Dr. Moss’s 46 patents. The GE turbosupercharger and the Whittle turbojet had similarities, including advanced impellers and turbines that operated in harsh environments.

When Dr. Moss died in 1946 at age 74 of a heart ailment, GE was firmly established as a leading designer and producer of jet engines. At the very time the father of GE Aviation was eulogized, GE engineers in Lynn were busy designing the innovative J47 military turbojet — the most produced jet engine in history.

 

The past, present and future of flight in one photo. On the left, the 1919 turbosupercharger. On the right, the GE9X engine.