Turbojet (Inventions)

The invention: A jet engine with a turbine-driven compressor that uses its hot-gas exhaust to develop thrust.

The people behind the invention:

Henry Harley Arnold (1886-1950), a chief of staff of the U.S.
Army Air Corps Gerry Sayer, a chief test pilot for Gloster Aircraft Limited Hans Pabst von Ohain (1911- ), a German engineer Sir Frank Whittle (1907-1996), an English Royal Air Force officer and engineer

Developments in Aircraft Design

On the morning of May 15, 1941, some eleven months after France had fallen to Adolf Hitler’s advancing German army, an experimental jet-propelled aircraft was successfully tested by pilot Gerry Sayer. The airplane had been developed in a little more than two years by the English company Gloster Aircraft under the supervision of Sir Frank Whittle, the inventor of England’s first jet engine.
Like the jet engine that powered it, the plane had a number of predecessors. In fact, the May, 1941, flight was not the first jet-powered test flight: That flight occurred on August 27,1939, when a Heinkel aircraft powered by a jet engine developed by Hans Pabst von Ohain completed a successful test flight in Germany. During this period, Italian airplane builders were also engaged in jet aircraft testing, with lesser degrees of success.
Without the knowledge that had been gained from Whittle’s experience in experimental aviation, the test flight at the Royal Air Force’s Cranwell airfield might never have been possible. Whittle’s repeated efforts to develop turbojet propulsion engines had begun in 1928, when, as a twenty-one-year-old Royal Air Force (RAF) flight cadet at Cranwell Academy, he wrote a thesis entitled “Future Developments in Aircraft Design.” One of the principles of Whittle’s earliest research was that if aircraft were eventually to achieve very high speeds over long distances, they would have to fly at veryhigh altitudes, benefiting from the reduced wind resistance encountered at such heights.
Whittle later stated that the speed he had in mind at that time was about 805 kilometers per hour—close to that of the first jet-powered aircraft. His earliest idea of the engines that would be necessary for such planes focused on rocket propulsion (that is, “jets” in which the fuel and oxygen required to produce the explosion needed to propel an air vehicle are entirely contained in the engine, or, alternatively, in gas turbines driving propellers at very high speeds). Later, it occurred to him that gas turbines could be used to provide forward thrust by what would become “ordinary” jet propulsion (that is, “thermal air” engines that take from the surrounding atmosphere the oxygen they need to ignite their fuel). Eventually, such ordinary jet engines would function according to one of four possible systems: the so-called athodyd, or continuous-firing duct; the pulsejet, or intermittent-firing duct; the turbojet, or gas-turbine jet; or the propjet, which uses a gas turbine jet to rotate a conventional propeller at very high speeds.

Passing the Test

The aircraft that was to be used to test the flight performance was completed by April, 1941. On April 7, tests were conducted on the ground at Gloster Aircraft’s landing strip at Brockworth by chief test pilot Sayer. At this point, all parties concerned tried to determine whether the jet engine’s capacity would be sufficient to push the aircraft forward with enough speed to make it airborne. Sayer dared to take the plane off the ground for a limited distance of between 183 meters and 273 meters, despite the technical staff’s warnings against trying to fly in the first test flights.
On May 15, the first real test was conducted at Cranwell. During that test, Sayer flew the plane, now called the Pioneer, for seventeen minutes at altitudes exceeding 300 meters and at a conservative test speed exceeding 595 kilometers per hour, which was equivalent to the top speed then possible in the RAF’s most versatile fighter plane, the Spitfire.
Once it was clear that the tests undertaken at Cranwell were not only successful but also highly promising in terms of even better performance, a second, more extensive test was set for May 21,1941. It was this later demonstration that caused the Ministry of Air Production (MAP) to initiate the first steps to produce the Meteor jet fighter aircraft on a full industrial scale barely more than a year after the Cranwell test flight.


Since July, 1936, the Junkers engine and aircraft companies in Hitler’s Germany had been a part of a new secret branch dedicated to the development of a turbojet-driven aircraft. In the same period, Junkers’ rival in the German aircraft industry, Heinkel, Inc., approached von Ohain, who was far enough along in his work on the turbojet principle to have patented a device very similar to Whittle’s in 1935. A later model of this jet engine would power a test aircraft in August, 1939.
In the meantime, the wider impact of the flight was the result of decisions made by General Henry Harley Arnold, chief of staff of the U.S. Army Air Corps. Even before learning of the successful flight in May, he made arrangements to have one of Whittle’s engines shipped to the United States to be used by General Electric Company as a model for U.S. production. The engine arrived in October, 1941, and within one year, a General Electric-built engine powered a Bell Aircraft plane, the XP-59 A Airacomet, in its maiden flight.
The jet airplane was not perfected in time to have any significant impact on the outcome of World War II, but all of the wartime experimental jet aircraft developments that were either sparked by the flight in 1941 or preceded it prepared the way for the research and development projects that would leave a permanent revolutionary mark on aviation history in the early 1950′s.
See also Airplane; Dirigible; Rocket; Rocket; Stealth aircraft; Supersonic passenger plane; V-2 rocket.

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