Powered aircraft
Encyclopedia
A powered aircraft is an aircraft
that uses onboard propulsion
. This requires a power source
, and some method of coupling the power to the air in order to create a forward force or thrust. Some types also require power to provide lift.
A propeller or airscrew comprises a set of small, wing-like aerofoil blades set around a central hub which spins on an axis aligned in the direction of travel. The blades are set at a pitch
angle to the airflow, which may be fixed or variable, such that spinning the propeller creates aerodynamic lift, or thrust, in a forward direction.
A tractor
design mounts the propeller in front of the power source, while a pusher
design mounts it behind. Although the pusher design allows cleaner airflow over the wing, tractor configuration is more common because it allows cleaner airflow to the propeller and provides a better weight distribution
.
Contra-rotating propellers
have one propeller close behind another on the same axis, but rotating in the opposite direction.
A variation on the propeller is to use many broad blades to create a fan. Such fans are usually surrounded by a ring-shaped fairing or duct, as ducted fan
s.
Many kinds of power plant have been used to drive propellers.
The earliest designs used man power to give dirigible balloons some degree of control, and go back to Jean-Pierre Blanchard
in 1784. Attempts to achieve heavier-than-air man-powered flight did not succeed fully until Paul MacCready
's Gossamer Condor
in 1977.
The first powered flight was made in a steam-powered
dirigible by Henri Giffard
in 1852. Attempts to marry a practical lightweight steam engine
to a practical fixed-wing airframe did not succeed until much later, by which time the internal combustion engine was already dominant.
From the first controlled powered fixed-wing aircraft flight by the Wright brothers
until World War II
, propellers turned by the internal combustion piston engine
were virtually the only type of propulsion system in use. The piston engine is still used in the majority of smaller aircraft produced, since it is efficient at the lower altitudes and slower speeds suited to propellers.
Turbine engines need not be used as jets (see below), but may be geared to drive a propeller in the form of a turboprop
. Modern helicopters also typically use turbine engines to power the rotor. Turbines provide more power for less weight than piston engines, and are better suited to small-to-medium size aircraft or larger, slow-flying types. Some turboprop designs mount the propeller directly on an engine turbine shaft, and are called propfan
s.
Other less common power sources include:
s provide thrust by taking in air, burning it with fuel in a combustion chamber
, and accelerating the exhaust rearwards so that it ejects at high speed. The reaction against this acceleration provides the engine thrust.
Jet engines can provide much higher thrust than propellers, and are naturally efficient at higher altitudes, being able to operate above 40000 ft (12,192 m). They are also much more fuel-efficient at normal flight speeds than rocket
s. Consequently, nearly all high-speed and high-altitude aircraft use jet engines.
The early turbojet and modern turbofan
use a spinning turbine to create airflow for takeoff and to provide thrust. Many, mostly in military aviation, add an afterburner
which injects extra fuel into the hot exhaust.
Use of a turbine is not absolutely necessary: other designs include the crude pulse jet
, high-speed ramjet
and the still-experimental supersonic-combustion ramjet or scramjet
. These mechanically simple designs require an existing airflow to work and cannot work when stationary, so they must be launched by a catapult or rocket booster, or dropped from a mother ship.
The bypass turbofan engines of the Lockheed SR-71
were a hybrid design – the aircraft took off and landed in jet turbine configuration, and for high-speed flight the afterburner was lit and the turbine bypassed, to create a ramjet.
The motorjet
was a very early design which used a piston engine in place of the combustion chamber, similar to a turbocharged
piston engine except that the thrust is derived from the turbine instead of the crankshaft. It was soon superseded by the turbojet and remained a curiosity.
s) have spinning blades called a rotor which spins in the horizontal plane to provide lift. Forward thrust is obtained by angling the rotor disc slightly forward so that a proportion of its lift is directed forwards.
The rotor of a helicopter may, like a propeller, be powered by a variety of methods such as an internal-combustion engine or jet turbine. Tip jets, fed by gases passing along hollow rotor blades from a centrally mounted engine, have been experimented with. Attempts have even been made to mount engines directly on the rotor tips.
propulsion offers very hight thrust for light weight and has no height limit, but suffers from high fuel consumption and the need to carry oxidant as well as propellant.
Rocket-powered aircraft have been experimented with, and during the Second World War the Messerschmitt Komet
fighter was developed and used operationally.
Since then they have been restricted to specialised niches, such as the Bell X-1
which broke the sound barrier or the North American X-15
which was capable of flying at extremely high altitudes at the border with space as it was not dependent on atmospheric oxygen.
Rockets have more often been used as a supplement to the main powerplant, typically in the case of rocket-assisted take off to give more power for a heavily loaded aircraft or reduce the takeoff run. In a number of designs such as the prototype "mixed-power" Saunders-Roe SR.53
interceptor
a rocket was used to provide high-speed climb and speed to reach the target while a smaller turbojet provided a slower and more economical return to base.
component.
Working devices have been created for fight research and as prototypes, but the vertical oscillation of the fuselage, which tends to accompany the wing flapping, limits their usefulness. The only practical application is a flying model hawk used to freeze prey animals into stillness so that they can be captured.
Toys in the form of a flying model bird are also popular.
obtains lift from airflow over the wing resulting from motion due to forward thrust. A few other types, such as the rotary-winged autogyro
, obtain lift through similar methods.
Some types use a separate power system to create lift. These include the rotary-winged helicopter
and craft that use lift jet
s (e.g. the flying bedstead
).
A hot air balloon
requires a power source (normally a gas burner) for lift, but is not normally considered a "powered aircraft".
Information
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
that uses onboard propulsion
Air propulsion
Air propulsion is the generation of thrust during flight by an aircraft or a creature such as a bird, bat or insect.-Aircraft:An aircraft propulsion system must serve two purposes. First, the thrust from the propulsion system must balance the drag of the airplane when the airplane is cruising...
. This requires a power source
Aircraft engine
An aircraft engine is the component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines...
, and some method of coupling the power to the air in order to create a forward force or thrust. Some types also require power to provide lift.
Propeller aircraft
Blade pitch
Blade pitch or simply pitch refers to turning the angle of attack of the blades of a propeller or helicopter rotor into or out of the wind to control the production or absorption of power. Wind turbines use this to adjust the rotation speed and the generated power...
angle to the airflow, which may be fixed or variable, such that spinning the propeller creates aerodynamic lift, or thrust, in a forward direction.
A tractor
Tractor configuration
thumb|right|[[Evektor-Aerotechnik|Aerotechnik EV97A Eurostar]], a tractor configuration aircraft, being pulled into position by its pilot for refuelling....
design mounts the propeller in front of the power source, while a pusher
Pusher configuration
In a craft with a pusher configuration the propeller are mounted behind their respective engine. According to Bill Gunston, a "pusher propeller" is one mounted behind engine so that drive shaft is in compression...
design mounts it behind. Although the pusher design allows cleaner airflow over the wing, tractor configuration is more common because it allows cleaner airflow to the propeller and provides a better weight distribution
Weight distribution
Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes, and trains.In a vehicle which relies on gravity in some way, weight distribution directly affects a variety of vehicle characteristics, including handling, acceleration, traction, and component life...
.
Contra-rotating propellers
Contra-rotating propellers
Aircraft equipped with contra-rotating propellers, also referred to as coaxial contra-rotating propellers, apply the maximum power of usually a single piston or turboprop engine to drive two propellers in contra-rotation...
have one propeller close behind another on the same axis, but rotating in the opposite direction.
A variation on the propeller is to use many broad blades to create a fan. Such fans are usually surrounded by a ring-shaped fairing or duct, as ducted fan
Ducted fan
A ducted fan is a propulsion arrangement whereby a fan, which is a type of propeller, is mounted within a cylindrical shroud or duct. The duct reduces losses in thrust from the tip vortices of the fan, and varying the cross-section of the duct allows the designer to advantageously affect the...
s.
Many kinds of power plant have been used to drive propellers.
The earliest designs used man power to give dirigible balloons some degree of control, and go back to Jean-Pierre Blanchard
Jean-Pierre Blanchard
Jean-Pierre Blanchard , aka Jean Pierre François Blanchard, was a French inventor, most remembered as a pioneer in aviation and ballooning....
in 1784. Attempts to achieve heavier-than-air man-powered flight did not succeed fully until Paul MacCready
Paul MacCready
Paul B. MacCready, Jr. was an American aeronautical engineer. He was the founder of AeroVironment and the designer of the human-powered aircraft that won the Kremer prize...
's Gossamer Condor
Gossamer Condor
-See also:-Further reading:*Morton Grosser. Gossamer Odyssey: The Triumph of Human-Powered Flight. MBI Press, 2004; Dover Publications, Inc., 1991; Houghton Mifflin Co., 1981*Morton Grosser. On Gossamer Wings. York Custom Graphics, 1982...
in 1977.
Steam aircraft
Steam aircraft are aircraft that are propelled by steam engines. They were unusual devices because of the difficulty in producing a powerplant with a high enough power-to-weight ratio to be practical...
dirigible by Henri Giffard
Henri Giffard
Henri Giffard was a French engineer. In 1852 he invented the steam injector and the powered airship.-Career:Baptiste Henri Jacques Giffard was born in Paris in 1825...
in 1852. Attempts to marry a practical lightweight steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
to a practical fixed-wing airframe did not succeed until much later, by which time the internal combustion engine was already dominant.
From the first controlled powered fixed-wing aircraft flight by the Wright brothers
Wright brothers
The Wright brothers, Orville and Wilbur , were two Americans credited with inventing and building the world's first successful airplane and making the first controlled, powered and sustained heavier-than-air human flight, on December 17, 1903...
until World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
, propellers turned by the internal combustion piston engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
were virtually the only type of propulsion system in use. The piston engine is still used in the majority of smaller aircraft produced, since it is efficient at the lower altitudes and slower speeds suited to propellers.
Turbine engines need not be used as jets (see below), but may be geared to drive a propeller in the form of a turboprop
Turboprop
A turboprop engine is a type of turbine engine which drives an aircraft propeller using a reduction gear.The gas turbine is designed specifically for this application, with almost all of its output being used to drive the propeller...
. Modern helicopters also typically use turbine engines to power the rotor. Turbines provide more power for less weight than piston engines, and are better suited to small-to-medium size aircraft or larger, slow-flying types. Some turboprop designs mount the propeller directly on an engine turbine shaft, and are called propfan
Propfan
A propfan was first defined as a small diameter, highly loaded multiple bladed variable pitch propulsor having swept blades with thin advanced airfoil sections, integrated with a nacelle contoured to retard the airflow through the blades thereby reducing compressibility losses and designed to...
s.
Other less common power sources include:
- Electric motors, often linked to solar panels to create a solar-powered aircraft.
- Rubber bands, wound many times to store energy, are mostly used for flying models.
Jet aircraft
Airbreathing jet engineAirbreathing jet engine
An airbreathing jet engine is a jet engine propelled by a jet of hot exhaust gases formed from air that is drawn into the engine via an inlet duct....
s provide thrust by taking in air, burning it with fuel in a combustion chamber
Combustion chamber
A combustion chamber is the part of an engine in which fuel is burned.-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber...
, and accelerating the exhaust rearwards so that it ejects at high speed. The reaction against this acceleration provides the engine thrust.
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s. Consequently, nearly all high-speed and high-altitude aircraft use jet engines.
The early turbojet and modern turbofan
Turbofan
The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...
use a spinning turbine to create airflow for takeoff and to provide thrust. Many, mostly in military aviation, add an afterburner
AfterBurner
The AfterBurner is a lighting solution for the Game Boy Advance system that was created by Triton-Labs.Originally, portablemonopoly.net was a website created to petition Nintendo to put some kind of light in their Game Boy Advance system...
which injects extra fuel into the hot exhaust.
Use of a turbine is not absolutely necessary: other designs include the crude pulse jet
Pulse jet engine
A pulse jet engine is a type of jet engine in which combustion occurs in pulses. Pulsejet engines can be made with few or no moving parts, and are capable of running statically....
, high-speed ramjet
Ramjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
and the still-experimental supersonic-combustion ramjet or scramjet
Scramjet
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow...
. These mechanically simple designs require an existing airflow to work and cannot work when stationary, so they must be launched by a catapult or rocket booster, or dropped from a mother ship.
The bypass turbofan engines of the Lockheed SR-71
SR-71 Blackbird
The Lockheed SR-71 "Blackbird" was an advanced, long-range, Mach 3+ strategic reconnaissance aircraft. It was developed as a black project from the Lockheed A-12 reconnaissance aircraft in the 1960s by the Lockheed Skunk Works. Clarence "Kelly" Johnson was responsible for many of the...
were a hybrid design – the aircraft took off and landed in jet turbine configuration, and for high-speed flight the afterburner was lit and the turbine bypassed, to create a ramjet.
The motorjet
Motorjet
A motorjet is a rudimentary type of jet engine which is sometimes referred to as thermojet, a term now commonly used to describe a particular and completely unrelated pulsejet design.- Design :...
was a very early design which used a piston engine in place of the combustion chamber, similar to a turbocharged
Turbocharger
A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...
piston engine except that the thrust is derived from the turbine instead of the crankshaft. It was soon superseded by the turbojet and remained a curiosity.
Rotorcraft
Rotorcraft (e.g. helicopterHelicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
s) have spinning blades called a rotor which spins in the horizontal plane to provide lift. Forward thrust is obtained by angling the rotor disc slightly forward so that a proportion of its lift is directed forwards.
The rotor of a helicopter may, like a propeller, be powered by a variety of methods such as an internal-combustion engine or jet turbine. Tip jets, fed by gases passing along hollow rotor blades from a centrally mounted engine, have been experimented with. Attempts have even been made to mount engines directly on the rotor tips.
Rocket-powered aircraft
RocketRocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
propulsion offers very hight thrust for light weight and has no height limit, but suffers from high fuel consumption and the need to carry oxidant as well as propellant.
Rocket-powered aircraft have been experimented with, and during the Second World War the Messerschmitt Komet
Messerschmitt Me 163
The Messerschmitt Me 163 Komet, designed by Alexander Lippisch, was a German rocket-powered fighter aircraft. It is the only rocket-powered fighter aircraft ever to have been operational. Its design was revolutionary, and the Me 163 was capable of performance unrivaled at the time. Messerschmitt...
fighter was developed and used operationally.
Since then they have been restricted to specialised niches, such as the Bell X-1
Bell X-1
The Bell X-1, originally designated XS-1, was a joint NACA-U.S. Army/US Air Force supersonic research project built by Bell Aircraft. Conceived in 1944 and designed and built over 1945, it eventually reached nearly 1,000 mph in 1948...
which broke the sound barrier or the North American X-15
North American X-15
The North American X-15 rocket-powered aircraft/spaceplane was part of the X-series of experimental aircraft, initiated with the Bell X-1, that were made for the USAAF/USAF, NACA/NASA, and the USN. The X-15 set speed and altitude records in the early 1960s, reaching the edge of outer space and...
which was capable of flying at extremely high altitudes at the border with space as it was not dependent on atmospheric oxygen.
Rockets have more often been used as a supplement to the main powerplant, typically in the case of rocket-assisted take off to give more power for a heavily loaded aircraft or reduce the takeoff run. In a number of designs such as the prototype "mixed-power" Saunders-Roe SR.53
Saunders-Roe SR.53
|- See also :-References:NotesBibliography* Jones, Barry. "Saro's Mixed Power Saga". Aeroplane Monthly, November 1994, Vol 22 No 11 Issue 259. pp. 32–39. London:IPC. ISSN 0143-7240....
interceptor
Interceptor aircraft
An interceptor aircraft is a type of fighter aircraft designed specifically to prevent missions of enemy aircraft, particularly bombers and reconnaissance aircraft. Interceptors generally rely on high speed and powerful armament in order to complete their mission as quickly as possible and set up...
a rocket was used to provide high-speed climb and speed to reach the target while a smaller turbojet provided a slower and more economical return to base.
Ornithopter
The ornithopter obtains thrust by flapping its wings. When the wing flaps, as opposed to gliding, it continues to develop lift as before, but the lift is rotated forward to provide a thrustThrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
component.
Working devices have been created for fight research and as prototypes, but the vertical oscillation of the fuselage, which tends to accompany the wing flapping, limits their usefulness. The only practical application is a flying model hawk used to freeze prey animals into stillness so that they can be captured.
Toys in the form of a flying model bird are also popular.
Methods of powering lift
A fixed-wing aircraftFixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...
obtains lift from airflow over the wing resulting from motion due to forward thrust. A few other types, such as the rotary-winged autogyro
Autogyro
An autogyro , also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust...
, obtain lift through similar methods.
Some types use a separate power system to create lift. These include the rotary-winged helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
and craft that use lift jet
Lift jet
A lift jet is a jet engine angled to provide an aircraft with aerostatic lift instead of thrust...
s (e.g. the flying bedstead
Flying bedstead
The Flying Bedstead was a nickname given to two completely different experimental vertical take-off and landing aircraft, both receiving the nickname because each comprised a skeletal platform raised on four legs that resembled a bedstead....
).
A hot air balloon
Hot air balloon
The hot air balloon is the oldest successful human-carrying flight technology. It is in a class of aircraft known as balloon aircraft. On November 21, 1783, in Paris, France, the first untethered manned flight was made by Jean-François Pilâtre de Rozier and François Laurent d'Arlandes in a hot air...
requires a power source (normally a gas burner) for lift, but is not normally considered a "powered aircraft".
External links
History- Prehistory of Powered Flight (U.S. Centennial of Flight Commission)
Information