War in the stratosphere, something new and memorable in the long history of battle, became a reality on July 25, 1941. Boeing Flying Fortresses on that date rained bombs on the German battleships Scharnhorst and Gneisenau in French ports from 35,000 feet. Though it was a summer day, the bombers were so high that they were covered with frost and the British Air Ministry announced that the attack took place at such a "fantastic" height that the scream of the bombs was probably the first warning.
This news came as no surprise, however, to the United States Army Air Corps nor to Dr Sanford A Moss, a bearded little General Electric Co engineer of Lynn, MA, and recipient of the 1940 Collier Trophy for his outstanding contribution to aviation. They saw nothing fantastic in the big Wright-engined planes carrying full bomb loads so high they were scarcely visible from the ground. In fact, they had been planning for this sort of thing with a great deal of patience and ingenuity for 23 years.
The Air Corps, especially the engineers at Wright Field, and Dr Moss pioneered the airplane supercharger, the device which permits aviation engines to "breathe" normally when aloft by forcing great power-producing quantities of air into their carburetors. To a very large degree, superchargers determine the height, speed and range of aircraft. These are vital factors in war and matters which the Air Corps and Dr Moss, who does not fly, have long pondered.
Three are two kinds of airplane superchargers. One type is gear-driven by the shaft of the engine itself. In the other, exhaust gases of the engine turn a turbine which operates a compressor sending air into the engine without appreciable drain on its power. The latter is know as the turbosupercharger. The Boeing Flying Fortresses which bombed the German battleships in July are equipped with this type. It was the first officially revealed use of the device in combat.
With the exception of a few small pleasure craft, every American airplane is equipped with at least a gear-driven supercharger. Turbosuperchargers, besides being part of the equipment of the latest Boeing bombers, are used in Republic's Lancer and Thunderbolt fighters and Lockheed's great interceptor pursuit ship, the P-38. The last named climbs a mile in the first minute and is designed to battle bombers above 35,000 feet. It is going to England as the Lightning.
Boyhood service as a mechanic trained Dr Moss for work on problems dealing with air pressure. He was born in San Francisco on Aug 23, 1872, and at age 16 was apprenticed as a mechanic in a San Francisco machine shop which made air compressors for mine work. In this period, he first became interested in doing things with air, and at the same time learned mechanical tricks which in later years gave him advantages in competition with scientists of only theoretical knowledge of the handling of air and gases moving with the power of a tornado.
After completing his four-year apprenticeship, he studied mechanical engineering at the University of California. To earn his expenses, he swept out the university machine shops, read to a blind student, drove a delivery wagon and corrected examination papers. He received a BS degree in 1896 and an MS degree in 1900. A thesis on the gas turbine earned him a Doctor of Philosophy degree and a job with General Electric in 1903.
He continued to work on this project at the West Lynn, MA, works of the company, but materials then available were not strong enough to withstand the strains in the proposed gas turbine. It had to be postponed, but, in the course of his work on it, he developed a number of devices, notably a centrifugal compressor which found wide use in blast furnaces and iron foundries. Because of the success of his compressors, Dr Moss was on of the men to whom the National Advisory Committee for Aeronautics turned when the United States entered the World War for a solution of the problem of giving war planes greater power. Dr William F Durand, NACA chairman, had been a member of the Cornell faculty during Moss's years there. The scientists of England, France and Germany were also at work on the problem. Dr Moss's answer was a wooden model of the turbosupercharger, which was essentially just a combination of his compressor and the gas turbine which had been shelved. Something similar had been tried in France but had not worked.
Col Howard C Marmon, a member of the famous Indianapolis motor car family, was then commander of McCook Field (now Wright Field). As soon as he saw the plane, he authorized a working model and one was rushed to completion. In their own words, the engineers said they had a device "to kid an airplane engine into thinking that it was at sea level." This was fitted to a Liberty motor and given a roaring ground test by Air Corps engineers at Dayton.
It performed so well that Col J G Vincent, who had succeeded to the McCook Field command, authorized a mountain top test for the turbosupercharger in the thin atmosphere which it was designed to conquer by forcing great quantities of power-producing air into the engine. Pike's Peak, 14.1009 feet high, was chosen as a site. Dr Moss, his assistant Waverly Reeves, an Army sergeant and four privates were designated for the test. This was performed in six weeks beginning in September, 1918, with snow often covering the equipment.
Without the supercharger, the Liberty engine which had given 350 hp at Dayton produced only 230 hp on the mountain top. With the supercharger, however, the engine actually produced 356 hp!
Maj R W Schroeder, then head of the Air Corps flight test section and now a United Air Lines vice president, states:
"The Armistice halted most World War research, including superchargers. However, the flight test section of the Air Corps headed by myself kept the supercharger project open with the result that Dr Moss was able to continue his work to more definite conclusion.
"Dr Moss and myself worked continuously together to keep this project from being shelved. We made the first flight of a supercharged engine before any other country had progressed beyond their ground experiments.
"The first flight ended at about 20,000 feet due to over-supercharging the engine, which in turn caused a connecting rod to break out through the crank case. On every flight thereafter something would fail at high altitudes during supercharging. Each time something was learned, corrective measures taken and tests resumed. On these flights test projects were set up each 5,000 feet starting at 20,000 feet, which was the normal ceiling of the Le Pere biplane with an unsupercharged Liberty engine.
"We were able to complete tests at 25,000-30,000 and 35,000 feet. It was during the test at 40,000 feet that I failed instead of the engine or the supercharger."
It was on Feb 27, 1920. Major Schroeder soared alone to 38,100 feet for probably the most dramatic record of all. At that level his oxygen supply was exhausted and he plunged unconscious for five miles but miraculously regained control of the plane near the ground and landed safely. The 67° below zero temperature which he encountered had frozen his eyeballs and he spent some time in a hospital.
On Sept 29,1921, Lieut J A Macready took the same plane up to 40,800 feet and Major Schroeder, out of the Army by then, telegraphed congratulations on "winning the crown of icicles." Nobody had ever flown so high. Later, Capts St Clair Streett and Albert W Stevens of Wright Field set a two-man record in a turbosupercharged plane by flying to 37,854 feet to make aerial photographs.
The altitude records, however, were incidental to the turbosupercharger development which aimed not only to send a plane to high altitudes but to give it speed and power over a wide range of altitudes. To this end, E T Jones, Adolph Berger, Opie Chenoweth and a succession of engineering and flying officers labored for years at Wright Field. Dr Moss, Samuel R Puffer, Edward B Clarke, W H Allen, C H Auger and other General Electric men also worked on the technical problems involved.
Something of what had been achieved was revealed in 1939 when Capt CS ("Bill") Irvine and Capt Pearl Robey flew a Boeing B-17 Flying Fortress coast-to-coast in 9 hrs 14½ min, never dropping below 20,000 feet and flying for a time at 33,000 feet for an average of 267 mph for the 2,460 mile flight. Capt Leonard F Herman was co-pilot, Mark Koogler, mechanic, and Louis Sibilsky, aeronautical engineer, both of Wright Field, completed the crew.
The superchargers, however, were not recognized as promptly as their Air Corps backers and Dr Moss would have liked. In an effort to increase their popularity, he fitted some automobiles with them, and cars, so equipped, one driven by Pete de Palo, took honors at the Indianapolis Speedway.
Enthusiasts for the device, however, did not despair. Dr Moss piled up a total of 45 patents, mostly in this field and argued for the supercharger, particularly the turbosuperchargers, with Government officials and business executives, and in the pages of technical magazines. Of Dr Moss, the editor of Mechanical Engineering once wrote:
"Painstaking, nervous, his eyes sparkling with fun or fury, Dr Moss raises his pointed beard in his companion's face and looks at him through the lower lenses of his glasses. His tongue, trying to keep up with an agile mind, is ready for a persistent barrage of embarrassing questions or a volley of explanations. He possesses that disarming characteristic of small boys with whom it is impossible to be angry for long in spite of sometimes exasperating behavior. Once you have met him you never forget him, but think of him in terms of warm affection."
It was difficult to appreciate the extraordinary engineering involved in the turbosupercharger. The turbine revolved at 20,000 or more rpm from the pressure of exhaust fumes at 1,500° Fahrenheit. Manifolds and turbine buckets were red hot while on the same drive shaft, only a few inches away, the compressor handled atmosphere as low as 76° below zero. At 22,000 rpm in a circle less than a foot in diameter, and weighing less than one hundredth of a pound, one of the tiny buckets was subjected to a centrifugal pull of around 1,750 pounds.
There was a much prompter welcome for Dr Moss's geared superchargers which first began to attract attention around 1926. Advances in metals and manufacturing processes by that time had produced materials capable of withstanding the great stresses involved in this type of mechanical arrangement. A geared supercharger is a small centrifugal compressor, usually weighing four pounds or less, which is built into an airplane engine and which obtains its power by gears from the engine crankshaft. Gears range in ration as high as 14 to 1 and with an engine speed of 2,000 rpm, the impeller turns at 28,000 rpm.
While the geared supercharger did not hold the high altitude possibilities of the turbo type, it could take a plane up to 15,000 feet or so and was particularly efficient at the precise level for which it was geared. It was soon evident that it was a great advance over everything earlier in the commercial field and manufacturer to manufacturer redesigned his engines in accordance with Dr Moss's ideas and his company, a pioneer in the making of turbines of all kinds, supplied the high impellers to all.
Some three-fourths of the engines made in 1929 had geared superchargers, and their use increased steadily until they became virtually standard equipment. Until 1938 all were of the Moss designs and possibly 95 percent of those made today are his types. The Air Corps, operating under depression budgets, found some money for turbosuperchargers, but Dr Moss on January 1, 1938, went into what he thought would be retirement without having all his dreams for these realized.
In retirement, Dr Moss began to devote himself to his numerous hobbies. One of these was searching for fragments of the wall that Romans built around London about 120 AD. He had listed 30 of these, including several not in guidebooks, and was in London working on the project the day the Munich pact was signed. The sequence of events unleashed by this took Dr Moss out of retirement and back to his superchargers.
At the age of 69, as a consulting engineer, he is now helping a galaxy of production experts to turn out the equipment, secret as to the latest models, on a mass basis. Orders and production have increased astronomically. The General Electric River Works at Lynn, MA, where Dr Moss and four other men once turned out the country's entire supercharger production have been greatly enlarged. Production has already started on a new $5,000,000 plant for this purpose at Everett, MA, and General Electric is now starting work on a third $20,000,000 supercharger plant at Fort Wayne, IN.
All of which is a matter of quiet pride to bright-eyed Dr Moss.
"First they told me it couldn't be done," he explains. "Then they said, 'What's the good of it?' and now what do they say? They say, 'we were going to do it all the time'."
No account of Dr Moss would be complete without something about his hobbies. Among the things presented to him at a dinner on his "retirement" were a score of new 25-cent pieces as material for his "matching" hobby. In the interest of proving the law of probabilities, he has been matching quarters with his friends for many years. He insists that this is not gambling as, in the long run, he will come out even.
Genealogical research is on of his interests. He has prepared family trees of many of his own and his family's ancestral lines by ferreting out scores of distant relatives.
Dr Moss is also well known in New England for his encounters with traffic officers in the suburbs of Boston. He once attempted to show by mathematical calculations that a policeman could not have overtaken him in such a short distance if he had been going as fast as charged. The judge listened and said, "Have you any more to say? It has cost you $5 so far."
Dr Moss said no more. At another time, he gave his driver's license to an officer in the middle of the highway as required and then refused to pull over to the side as directed on the grounds that Massachusetts law forbids operation of a car without an operator's license and the officer had his license!
This article was originally published in the March, 1942, issue of Flying and Popular Aviation magazine, vol 30, no 3, pp 36-38, 114, 121.
The PDF of this article includes photos of P-38, B-17C, and some early turbocharger setups, and a diagram of a turbosupercharger.
Photos are not credited.