Jet aircraft
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 person who attempted to build rotor-less plane in 1910 — the Coanda-1910, but because of various faults in the design his plane only flew once. 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.
History
The concept of the jet engine was developed during the 1920s and '30s independently by Frank Whittle and Hans von Ohain. 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. It was the first jet aircraft recognised by the Fédération Aéronautique Internationale (at the time the german He 178 program wasn't yet revealed to public).
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. USSR tested its own Bereznyak-Isayev BI-1 in 1942, but the project was scrapped by Stalin in 1945. 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).
Modern jet aircraft
Modern airliners cruise at speeds of 0.75 to 0.85 Mach, or 75% to 85% of the speed of sound.
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 an aircraft during ascent, nor during reentry and landing (as it is unpowered during this phase of operation).
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:
- turbojet
- turbofan (which come in two main forms low bypass turbofan and high bypass turbofan)
- rocket
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
- Aircraft broker
- Jumbo jet
- Jet airliner
- Commercial aviation
- Contrail
- Range (aircraft) the range can be calculated using the Breguet range equation.
- Very light jet
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