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From Wikipedia, the free encyclopedia

A jet aircraft is an aircraft propelled by jet engines. Jet aircraft generally fly much faster than propeller-powered aircraft and at higher altitudes — as high as 10,000 to 15,000 meters (about 33,000 to 49,000 ft). At these altitudes, jet engines achieve maximum efficiency over long distances. The engines in propeller powered aircraft achieve their maximum efficiency at much lower altitudes. Jet aircraft can move faster than sound.

Henri Coandă, a Romanian Engineer, was the first to build a jet plane in 1910 — the Coanda-1910. Later on, two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently during the late 1930s. The concept had already been discussed as early as August 1928 by Frank Whittle at Flying School, Wittering, but Hans von Ohain also wrote in February 1936 to Ernst Heinkel, telling him of the design and its possibilities. However, it can be argued that A. A. Griffith, who published a paper in July 1926 on compressors and turbines, which he had been studying at the RAE, also deserves priority credit.

Contents

History

Heinkel He 178, the world's first aircraft to fly purely on turbojet power
Frank Whittle's memorial showing a full-scale model of the Gloster E28/39

The first turbine-equipped jetplane was designed on paper in late 1929 when Frank Whittle of the British Royal Air Force sent his concept to the Air Ministry to see if it would be of any interest to them. The first manufactured turbine jetplane was the Heinkel He 178 turbojet prototype of the German Air Force (Luftwaffe), piloted by Erich Warsitz on August 27, 1939.[1]

The first flight of the Italian Caproni Campini N.1 motorjet prototype was on August 27, 1940. Test pilot Major Mario De Bernardi of the Regia Aeronautica was at the controls.

The British flew their Gloster E.28/39 prototype on May 15, 1941, powered by Sir Frank Whittle's turbojet, and piloted by Flt Lt PG Sayer. When the United States learned of the British work, it produced the Bell XP-59 with a version of the Whittle engine built by General Electric, which flew on September 12, 1942, piloted by Col L. Craigie.

The first operational jet fighter was the Messerschmitt Me 262, made by Germany during late World War II. It was the fastest conventional aircraft of World War II — although the rocket-powered Messerschmitt Me 163 Komet was faster. Mass production started in 1944, too late for a decisive effect on the outcome of the war. About the same time, the United Kingdom's Gloster Meteor was limited to defense of the UK against the V1 flying bomb and ground-attack operations over Europe in the last months of the war. The Imperial Japanese Navy also developed jet aircraft in 1945, including the Nakajima J9Y Kikka, a crude copy of the Me-262.

On November 8, 1950, during the Korean War, United States Air Force Lt. Russell J. Brown, flying in an F-80, intercepted two North Korean MiG-15s near the Yalu River and shot them down in the first jet-to-jet dogfight in history.

BOAC operated the first commercial jet service, from London to Johannesburg, in 1952 with the de Havilland Comet jetliner.

The fastest military jet plane was the SR-71 Blackbird at Mach 3.35 (2275 MPH). The fastest commercial jet plane was the Tupolev Tu-144 at Mach 2.35 (1555 MPH). A jet is also the fastest of the plane family.

Modern jet aircraft

Bahrain Royal Flight Boeing 747SP

Modern airliners cruise at speeds of 0.75 to 0.85 Mach, or 75% to 85% of the speed of sound (420 to 580 mph/ 680-900 km/h). The speed of sound predominantly depends on air temperature (hardly at all on pressure), so the Mach number for the speed of a jet also varies with atmospheric conditions. NASA and the US Federal Aviation Administration have been promoting Very Light Jets: small general aviation aircraft seating 4 to 8 passengers.

Other jets

Most people use the term 'jet aircraft' to denote gas turbine based airbreathing jet engines, but rockets and scramjets are both also propelled by them.

The fastest airbreathing jet aircraft is the unmanned X-43 scramjet at around Mach 9-10. The fastest manned (rocket) aircraft is the X-15 at Mach 6.85.

The Space Shuttle, while far faster than the X-43 or X-15, is not regarded as a jet aircraft during ascent, nor during reentry and landing (as it is unpowered during this phase of operation).

The shape of most airliners is usually designed to have nearly the same cross-sectional area at each point along its length as the Sears-Haack body

Aerodynamics

Many jet aircraft fly at high speeds, either supersonic or speeds just below the speed of sound ("transonic"). Aerodynamics is therefore an important consideration.

Jet aircraft are usually designed using the Whitcomb area rule, which says that the cross-section of the aircraft at any point must be approximately the same as the Sears-Haack body. This minimises the production of shockwaves which would waste energy.

Jet engines

Jet engines come in several main types:

The types are used for different aircraft. Turbojets are seldom used, but was used on Concorde; it has a high exhaust speed and low frontal cross-section, and so is best suited to high-speed flight. Low bypass turbofans have a lower exhaust speed than turbojets and are used for transonic and low supersonic speeds. High bypass turbofans are used for subsonic aircraft and are quite efficient and are widely used for airliners.

Rockets have extremely fast exhaust speeds and are mainly used when high speeds or extremely high altitudes are needed.

See also

Bibliography

  • Lutz Warsitz: THE FIRST JET PILOT - The Story of German Test Pilot Erich Warsitz, Pen and Sword Books Ltd., England, 2009, ISBN 9781844158188, English Edition

External Links

References

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Simple English

Jet aircraft are aircraft with jet engines. Unlike propeller-powered aircraft, jet aircraft normally fly at altitudes as high as 10,000 to 15,000 meters, about 33,000 to 49,000 feet (14,900 m). At these altitudes, jet engines can achieve maximum efficiency over long distances. The engines in propeller powered aircraft achieve their maximum efficiency at much lower altitudes.

Jets come in different sizes, the biggest are used by airlines to move people and things, while the smallest are called Fighters, and are used in war. An example of each is the Boeing 747 and the F-22 Raptor


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