A jet aircraft (or simply jet) is an aircraft (nearly always a
fixed-wing aircraft) propelled by jet engines (jet propulsion).
Whereas the engines in propeller-powered aircraft generally achieve
their maximum efficiency at much lower speeds and altitudes, jet
engines and aircraft achieve maximum efficiency (see specific impulse)
at speeds close to or even well above the speed of sound. Jet aircraft
generally cruise at faster than about Mach 0.8 (609 mph,
981 km/h or 273 m/s) at altitudes around 10,000–15,000
metres (33,000–49,000 ft) or more.
Frank Whittle, an English inventor and
RAF officer, developed the
concept of the jet engine in 1928, and
Hans von Ohain
Hans von Ohain in Germany
developed the concept independently in the early 1930s. He wrote in
February 1936 to Ernst Heinkel, who led the construction of the
world's first turbojet aircraft and jet plane Heinkel He 178. However,
it can be argued that the English engineer A. A. Griffith, who
published a paper in July 1926 on compressors and turbines, also
2 Other jets
4 Jet engines
5 Flying characteristics
6 Propulsive efficiency
8 See also
10 External links
Heinkel He 178, in August 1939 the world's first aircraft to fly
purely on turbojet power
Caproni Campini N1
Caproni Campini N1 in flight
After the first instance of powered flight, a large number of jet
powerplants were suggested. René Lorin, Morize, Harris proposed
systems for creating a jet efflux. In 1910 the Romanian inventor
Henri Coandă filed a patent on a jet propulsion system which used
piston-engine exhaust gases to add heat to an otherwise pure air
stream compressed by rotating fan blades in a duct. It was installed
Coandă-1910 but this craft probably never flew.
Rocket-powered jet aircraft were pioneered in Germany. The first
aircraft to fly under rocket power was the Lippisch Ente, in 1928.
The Ente had previously been flown as a glider. The next year, in
Opel RAK.1 became the first purpose-built rocket plane to
The "turbojet", was invented in the 1930s, independently by Frank
Whittle and later Hans von Ohain. The first turbojet aircraft to fly
Heinkel He 178
Heinkel He 178 V1 first prototype of the German Air Force, the
Luftwaffe, on August 27, 1939 in
The first flight of a jet engined aircraft to come to popular
attention was the Italian
Caproni Campini N.1
Caproni Campini N.1 motorjet prototype that
flew on August 27, 1940. It was the first jet aircraft recognised
Fédération Aéronautique Internationale
Fédération Aéronautique Internationale (at the time the
German He 178 program was still kept secret). Campini had proposed the
motorjet in 1932.
The British experimental
Gloster E.28/39 first took to the air on May
15, 1941, powered by Sir Frank Whittle's turbojet. The United
States produced the Bell XP-59A using two examples of a version of the
Whittle engine built by General Electric, which flew on October 1,
1942. The Meteor was the first production jet as it entered production
a few months before the Me 262 ,which itself had been
in development since before the start of the war as Projekt 1065.
A modern reproduction of the Me 262 in flight in 2006. The first two
operational turbojet aircraft, the
Messerschmitt Me 262
Messerschmitt Me 262 and then the
Gloster Meteor entered service in 1944.
The first operational jet fighter was the Messerschmitt Me 262,
made by Germany during World War II, and entered service on 19 April
1944 with Erprobungskommando 262 at Lechfeld just south of Augsburg.
It was the fastest conventional aircraft of World War II –
although there were faster aircraft propelled by unconventional means,
such as the rocket-powered Messerschmitt Me 163 Komet. The
Messerschmitt Me 262
Messerschmitt Me 262 had first flown on April 18, 1941, with initial
plans drawn up by Dr Waldemar Voigt's design team in April 1939, but
mass production did not start until early 1944 with the first
squadrons operational that year, too late for a decisive effect on the
outcome of the war.
Gloster Meteor F.3s. The
Gloster Meteor was the first British jet
fighter and the Allies' only jet aircraft to achieve combat operations
during World War II.
About the same time, mid 1944, the United Kingdom's
Gloster Meteor was
being committed to defence of the UK against the V-1 flying
bomb – itself a pulsejet-powered aircraft and direct
ancestor of the cruise missile– and then ground-attack operations
over Europe in the last months of the war. In 1944 Germany introduced
into service the
Arado Ar 234
Arado Ar 234 jet reconnaissance and bomber, though
chiefly used in the former role, with the
Heinkel He 162
Heinkel He 162 Spatz
single-jet light fighter premiering as 1944 ended. USSR tested its own
Bereznyak-Isayev BI-1 in 1942, but the project was scrapped by Joseph
Stalin in 1945. The
Imperial Japanese Navy
Imperial Japanese Navy also developed jet aircraft
in 1945, including the Nakajima J9Y Kikka, a modified, and slightly
smaller version of the Me 262 that had folding wings. By the end of
1945, the US had introduced their first jet fighter, the Lockheed P-80
Shooting Star into service and the UK its second fighter design, the
de Havilland Vampire.
The Boeing 737-300, part of the
Boeing 737 family is the most produced
jet aircraft that is still operating.
The US introduced the North American B-45 Tornado, their first jet
bomber, into service in 1948. Although capable of carrying nuclear
weapons it was used for reconnaissance over Korea. 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
Yalu River and shot them down in the first jet-to-jet dogfight in
history. The UK put the
English Electric Canberra
English Electric Canberra into service in 1951
as a light bomber. It was designed to fly higher and faster than any
BOAC Comet 1 was the first passenger jet airliner
BOAC operated the first commercial jet service, from
Johannesburg, in 1952 with the de Havilland Comet jetliner. This
highly innovative aircraft travelled far faster and higher than the
propeller aircraft, was much quieter, smoother, and had stylish
blended wings containing hidden jet engines. However, due to a design
defect, and use of aluminum alloys, the aircraft suffered catastrophic
metal fatigue which led to several crashes.
The series of crashes gave time for the
Boeing 707 to enter service in
1958 and this came to dominate the market for civilian airliners. The
underslung engines were found to be advantageous in the event of a
propellant leak, and so the 707 looked rather different from the
Comet: the 707 has a shape that is effectively the same as that of
contemporary aircraft, with marked commonality still evident today for
example with the 737 (fuselage) and A340 (single deck, swept wing,
four below-wing engines).
Turbofan aircraft began entering service in the 1950s and 1960s,
bringing far greater fuel efficiency, and this is the type of jet in
widespread use today.
Tu-144, the world's first commercial supersonic transport aircraft
Tu-144 supersonic transport was the fastest commercial jet plane
at Mach 2.35 (1,555 mph, 2,503 km/h). It went into service
in 1975, but soon stopped flying. The Mach 2
Concorde aircraft entered
service in 1976 and flew for 27 years.
The fastest military jet plane was the
SR-71 Blackbird at Mach 3.35
(2,275 mph, 3,661 km/h).
Most people use the term 'jet aircraft' to denote gas turbine based
airbreathing jet engines, but rockets and scramjets are both also
propelled by jet propulsion.
Cruise missiles are single-use unmanned jet aircraft, powered
predominately by ramjets or turbojets or sometimes turbofans, but they
will often have a rocket propulsion system for initial propulsion.
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, was not
regarded as an aircraft during ascent as it was carried ballistically
by rocket thrust, rather than the air. During re-entry it was classed
(like a glider) as an unpowered aircraft. The first flight was in
Bell 533 (1964),
Lockheed XH-51 (1965), and Sikorsky S-69
(1977-1981) are examples of compound helicopter designs where jet
exhaust added to forward thrust. The
Hiller YH-32 Hornet
Hiller YH-32 Hornet and Fairey
Ultra-light Helicopter were among the many helicopters where the
rotors were driven by tip jets.
Jet-powered wingsuits exist - powered by model aircraft jet engines -
but of short duration and needing to be launched at height.
A McDonnell-Douglas DC-10, an example of a
Because of the way they work, the typical exhaust speed of jet engines
is transonic or faster, therefore most jet aircraft need to fly at
high speeds, either supersonic or speeds just below the speed of sound
("transonic") so as to achieve efficient flight. Aerodynamics is
therefore an important consideration.
Jet aircraft are usually designed using the Whitcomb area rule, which
says that the total area of cross-section of the aircraft at any point
along the aircraft from the nose must be approximately the same as
that of a Sears-Haack body. A shape with that property minimises the
production of shockwaves which would waste energy.
Main article: Jet engine
Jet engines come in several main types:
turbofan (which come in two main forms low bypass turbofan and high
The different types are used for different purposes.
Rockets are the oldest type and are mainly used when extremely high
speeds or extremely high altitudes are needed. Due to the extreme,
typically hypersonic, exhaust velocity and the necessity of oxidiser
being carried on board, they consume propellant extremely quickly. For
this reason, they are not practical for routine transportation.
Turbojets are the second oldest type; it has a high, usually
supersonic, exhaust speed and low frontal cross-section, and so is
best suited to high-speed, usually supersonic, flight. Although once
widely used, they are relatively inefficient compared to turboprop and
turbofans for subsonic flight. The last major aircraft to use
Tu-144 supersonic transports.
Low bypass turbofans have a lower exhaust speed than turbojets and are
mostly used for high sonic and transonic and low supersonic speeds.
High bypass turbofans are used for subsonic aircraft and are quite
efficient and are widely used for airliners.
Jet aircraft fly considerably differently to propeller aircraft.
One difference is that jet engines respond relatively slowly. This
complicates takeoff and landing maneuvers. In particular, during
takeoff, propeller aircraft engines blow air over their wings and that
gives more lift and a shorter takeoff. These differences caught out
BOAC Comet pilots.
Main article: Propulsive efficiency
In aircraft overall propulsive efficiency
is the efficiency, in percent, with which the energy contained in a
vehicle's propellant is converted into useful energy, to replace
losses due to air drag, gravity, and acceleration. It can also be
stated as the proportion of the mechanical energy actually used to
propel the aircraft. It is always less than 100% because of kinetic
energy loss to the exhaust, and less-than-ideal efficiency of the
propulsive mechanism, whether a propeller, a jet exhaust, or a fan. In
addition, propulsive efficiency is greatly dependent on air density
Mathematically, it is represented as
displaystyle eta =eta _ c eta _ p
displaystyle eta _ c
is the cycle efficiency and
displaystyle eta _ p
is the propulsive efficiency. The cycle efficiency, in percent, is
the proportion of energy that can be derived from the energy source
that is converted to mechanical energy by the engine.
Dependence of the propulsive efficiency (
displaystyle eta _ p
) upon the vehicle speed/exhaust speed ratio (v/c) for rocket and jet
For jet aircraft the propulsive efficiency (essentially energy
efficiency) is highest when the engine emits an exhaust jet at a speed
that is the same as, or nearly the same as, the vehicle velocity. The
exact formula for air-breathing engines as given in the
displaystyle eta _ p = frac 2 1+ frac c v
where c is the exhaust speed, and v is the speed of the aircraft.
Main article: Range (aircraft)
For a long range jet operating in the stratosphere, the speed of sound
is constant, hence flying at fixed angle of attack and constant Mach
number causes the aircraft to climb, without changing the value of the
local speed of sound. In this case:
is the cruise
Mach number and
the local speed of sound. The range equation can be shown to be:
displaystyle R= frac aM c_ T frac C_ L C_ D ln frac W_
1 W_ 2
which is known as the Breguet range equation after the French aviation
pioneer Louis Charles Breguet.
Very light jet
List of jet aircraft of World War II
^ Jet Propulsion of
Aircraft Part III G Geoffrey Smith Flight
September 25th 1941
^ "Lippisch Ente."[permanent dead link] The Internet Encyclopedia of
Science: Experimental Aircraft. Retrieved: 26 September 2011.
^ Warsitz, Lutz: The First Jet Pilot – The Story of German Test
Pilot Erich Warsitz (p. 125), Pen and Sword Books Ltd., England, 2009
^ Flight 28 August 1941
^ "No Airscrew Necessary..." Flight(flightglobal.com), 27 October 1949
^ Hecht, Heinrich. The World's First
Turbojet Fighter –
Messerschmitt Me 262. Atglen, Pennsylvania: Schiffer Publishing, 1990.
ISBN 0-88740-234-8.[page needed]
^ a b Jet! When Britain Ruled the Skies - BBC
^ Thomas Lawrence and David Jenney (31 Aug 2010). "The Fastest
Helicopter on Earth". IEEE Spectrum. Archived from the original on 30
January 2017. Retrieved 1 August 2017. CS1 maint: Uses authors
^ "'Jetman' Yves Rossy Shows Us How to Fly His Carbon Fiber Jet Wing".
Wired. 31 July 2013. Archived from the original on 2 January 2017.
Retrieved 1 August 2017.
^ K.Honicke, R.Lindner, P.Anders, M.Krahl, H.Hadrich, K.Rohricht.
Beschreibung der Konstruktion der Triebwerksanlagen. Interflug,
^ Spittle, Peter. "Gas turbine technology" p507, Rolls-Royce plc,
2003. Retrieved: 21 July 2012.
Lutz Warsitz: The First Jet Pilot – The Story of German Test Pilot
Erich Warsitz, Pen and Sword Books Ltd., England, 2009,
ISBN 978-1-84415-818-8, English Edition
Wikimedia Commons has media related to Jet-powered aircraft.
The official Erich Warsitz website (the world's first jet pilot),
inclusive rare videos (Heinkel He 178) and audio commentaries