A propeller can be seen as a rotating fin in water or a wing in air. The horizontal axis of rotation produces a dynamic force as thrust. The force produced is from the difference in pressure from the forward and rear surfaces of the blades. A fin is a surface used to produce thrust or to steer while traveling in water, air, or other fluid media. ... For some other uses of the word wing please see Wing (disambiguation). ... In physics, a net force acting on a body causes that body to accelerate; that is, to change its velocity. ... For the land-speed record breaking car, see ThrustSSC and Thrust2 For the computer game, see Thrust (computer game) Thrust is a reaction force described quantitatively by Newtons Second Law when a system expels or accelerates mass in one direction to propel a vehicle in the opposite direction. ...

Rotating the propeller on a US Navy EP-3E Orion's number four engine as part of preflight checks. The Orion is an anti-submarine warfare aircraft

Download high resolution version (500x703, 84 KB)Aviation Electricians Mate 3rd Class David Pennington rotates the propeller on an EP-3E Orions (anti-submarine warfare) number four engine as part of preflight checks. ... Download high resolution version (500x703, 84 KB)Aviation Electricians Mate 3rd Class David Pennington rotates the propeller on an EP-3E Orions (anti-submarine warfare) number four engine as part of preflight checks. ... The United States Navy (USN) is the branch of the United States armed forces responsible for naval operations. ... The Lockheed P-3 Orion is a patrol aircraft of the United States military used primarily for anti-submarine warfare. ... An Anti-submarine weapon is any weapon system designed explicitly to attack and destroy enemy submarines and other underwater devices. ...

Aircraft propellers

A propeller's efficiency is determined by (thrust × axial speed)/(resistance torque × rotational speed). Changes to a propeller's efficiency are produced by a number of factors, notably adjustments to the helix angle, the angle between the resultant relative velocity and the blade rotation direction, and to blade pitch. Very small pitch and helix angles give a good performance against resistance but provide little thrust, while larger angles have the opposite effect. The best helix angle is as if the blade was a wing producing much more lift than drag, roughly 45° in practice. However due to the shape of the propeller only part of the blade can actually be operating at peak efficiency, the outer part of the blade produces the most thrust and so the blade is positioned at a pitch that gives optimum angle to that portion. Since a large portion of the blade is therefore at an inefficient angle the inboard ends of the blade are subsumed into a streamlined spinner to reduce the resistance torque that would otherwise be created. Efficiency is the capability of acting or producing effectively with a minimum of waste, expense, or unnecessary effort. ... Flight dynamics is the study of orientation of air and space vehicles and how to control the critical flight parameters, typically named pitch, roll and yaw. ...

Very high efficiency propellers are similar in aerofoil section to a low drag wing and as such are poor in operation when at other than their optimum angle of attack. It required advanced control systems and better section profiling to counter the need for accurate matching of pitch to flight speed and engine speed to power so as to make these type of propellers usable. For a solid object moving through a fluid or gas, drag is the sum of all the aerodynamic or hydrodynamic forces in the direction of the external fluid flow. ...

However with a propeller at a pitch angle of 45° at low flight speeds the angle of attack will be high, possibly high enough to stall the airfoil. Since this is an extremely inefficient regime in which to operate the propeller, it means that most propellers are fitted with mechanisms to allow variable pitch - Coarse pitch for high speed flight and fine pitch for climbing or accelerating at lower speeds. Early pitch control settings were pilot operated and so limited to only three or so settings, later systems were automatic. Variable pitch was replaced with the constant speed mechanism. A stall is a (usually undesired) condition in aerodynamics and aviation. ...

Constant-speed propellers automatically adjust the blade pitch angle to alter resistance torque in response to sensed changes in RPM. Initially in a rather crude fashion with the pilot altering the setting via control of the propeller governor, but in more advanced aircraft the mechanism is linked into the entire engine management system for very fine control. The system is termed constant-speed because aeroengines produce maximum power at high revolutions and changing engine speed increases fuel consumption. It is, therefore, beneficial to run an engine at an optimum constant independent of flight speed, setting separate requirements for high power situations and cruising and controlling speed within these bands without changing RPM. A governor is a device used to measure and regulate the speed of a machine, such as an engine. ... An electronic control unit (ECU) (also known as an engine management system) is an electronic device, basically a computer, in an internal combustion engine that reads several sensors in the engine and uses the information to control the fuel injection and ignition systems of the engine. ... For information on the band, see Fuel (band). ...

A further consideration is the number and the shape of the blades used. Increasing the aspect ratio of the blades reduces drag but the amount of thrust produced depends on blade area, so using high aspect blades can lead to the need for a propeller diameter which is unusable. A further balance is that a smaller number of blades reduces interference effects between the blades, but to have sufficient blade area to transmit the available power within a set diameter means a compromise is needed. Increasing the number of blades also decreases the amount of work each blade is required to perform, limiting the local Mach number - a significant performance limit on propellers. Mach number (Ma) is defined as a ratio of speed to the speed of sound in the medium in case. ...

Contra-rotating propellers involve a second propeller rotating in the opposite direction immediately 'downstream' of the main propeller so as to recover energy lost in the swirling motion of the air in the propeller slipstream. Contra-rotation also increases power without increasing propeller diameter and provides a counter to the torque of high-power piston engines and the gyroscopic precession effects of the slipstream swirl. However on small aircraft the added cost, complexity, weight and noise of the system rarely make it worthwhile. Categories: Aircraft stubs ... A gyroscope is a device which demonstrates the principle of conservation of angular momentum, in physics. ...

The propeller is usually attached to the crankshaft of the engine, either directly or through a gearbox. Light aircraft sometimes forego the weight, complexity and cost of gearing but on larger aircraft and with turboprop engines it is essential. Crankshaft The crankshaft is that part of an engine which translates linear piston motion into rotation. ... A gearbox is an assembly of gears allowing the rotational speed of an input shaft to be changed to a different speed. ... A Turboprop or turboshaft engine is a type of gas turbine. ...

As mentioned, a propeller's performance suffers as the blade speed exceeds the speed of sound. As the relative air speed at the blade is rotation speed plus axial speed, a propeller blade will reach sonic speed sometime before the rest of the aircraft (with a theoretical blade the maximum aircraft speed is about 845 km/h (Mach 0.7) at sea-level, in reality it is rather lower). When a blade tip becomes supersonic, drag and torque resistance increase suddenly and shock waves form creating a sharp increase in noise. Aircraft with conventional propellers therefore do not usually fly faster than Mach 0.6 although there are certain craft, usually military, which do operate at Mach 0.8 or higher although there is considerable fall off in efficiency. Any speed over the speed of sound, which is approximately 343 m/s or 761 mph or 1,225 km/h at sea level, is said to be supersonic. ... For the vector animation platform, see Macromedia Shockwave. ...

Naturally there have been efforts to develop propellers for aircraft at high subsonic speeds. The 'fix' is similar to that of transonic wing design. The maximum relative velocity is kept as low as possible by careful control of pitch to allow the blades to have large helix angles; thin blade sections are used and the blades are swept back in a scimitar shape; a large number of blades are used to reduce work per blade and so circulation strength; contra-rotation is used. The propellers designed are more efficient than turbo-fans and in terms of cruising speed (Mach 0.7-0.85) suitable for airliners except that the noise is tremendous. The term scimitar refers to a sword with a curved blade from western Asia. ...

Aircraft Fans

A fan is a propeller with a large number of blades. A fan therefore produces a lot of thrust for a given diameter but the closeness of the blades means that each strongly affects the flow around the others. If the flow is supersonic this interference can be beneficial if the flow can be compressed through a series of shock waves rather than one. By placing the fan within a shaped duct -a ducted fan- specific flow patterns can be created depending on flight speed and engine performance. As air enters the duct its speed is reduced and pressure and temperature increased, if the aircraft is at a high subsonic speed this creates two advantages - the air enters the fan at a lower Mach speed and the higher temperature increases the local speed of sound. While there is a loss in efficiency as the fan is drawing on a smaller area of the free stream and so using less air, this is balanced by the ducted fan retaining efficiency at higher speeds where conventional propeller efficiency would be poor. A ducted fan or propeller also has certain benefits at lower speeds but the duct needs to be shaped in a different manner to one for higher speed flight. More air is taken in and the fan therefore operates at an efficiency equivalent to a larger unducted propeller, noise is also reduced by the ducting and should a blade become detached the duct would contain the damage. However the duct adds weight, cost, complexity and (to a certain degree) drag. A ducted fan is an arrangement of a propeller-driven aircraft where the propeller is mounted inside the fuselage, within a duct. ...

See also Propeller wind generator. A tall tower holds a wind turbine aloft where winds are consistently stronger. ...

Ship/Submarine propellers

Mechanical ship propulsion properly began with the steam ship. The first successful ship of this type is an issue of some debate; candidate inventors of the 18th century include William Symington, the Marquis de Jouffroy, John Fitch and many others. The American Robert Fulton is the most widely credited. Fulton's choice of paddle-wheels as the main motive source became standard on many of the following vessels (see Paddle steamer). Robert Fulton had tested, and rejected, the screw-propeller. A ship is a large, usually decked watercraft. ... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ... A steam engine is a heat engine that makes use of the potential energy that exists as pressure in steam, converting it to mechanical work. ... The first practieal steamboat was built by the engineer William Symington,1764 - 1831, born in the lead mining village of Leadhills, Lanarkshire, Scotland. ... John Fitch was born on January 21, 1743 in Hartford County, Connecticut. ... Robert Fulton (November 14, 1765 - February 24, 1815) was an American engineer and inventor widely credited with developing the first steam-powered ship. ... This article is about the boat propulsion implement, etc. ... A paddle steamer, paddleboat, or paddlewheeler is a ship driven by one or more paddle wheels driven by a steam engine. ...

Sketch of hand-cranked vertical and horizontal screws used in Bushnell's Turtle, 1775

The screw-propeller (as opposed to paddle-wheels) was introduced in the latter half of the 18th century. David Bushnell's invention of the submarine (the Turtle) in 1775 utilized hand-powered screws for vertical and horizontal propulsion. Josef Ressel designed and patented a screw propeller in 1827. Francis Petit Smith tested a screw propeller similar to Ressel's in 1836. In 1839, John Ericsson introduced the screw-propeller design onto a ship which then sailed over the Atlantic Ocean in 40 days. Mixed paddle and propeller designs were still being used at this time (vide the 1858 SS Great Eastern). David Bushnell (1742 - 1824) was a United States inventor during the American Revolutionary War. ... A cross-section sketch of Bushnells Turtle. ... Events February 9 - American Revolutionary War: British Parliament declares Massachusetts in rebellion March 23 - American Revolutionary War: Patrick Henry delivers his speech - give me liberty or give me death in Williamsburg, Virginia. ... Joseph Ludwig Franz Ressel (June 29, 1793- October 9, 1857) was an Austrian forest warden and the inventor of the ships propeller. ... Events February 20 - Battle of Huzaingo February 28 - The Baltimore & Ohio Railroad is incorporated, becoming the first railroad offering commercial transportation of both people and freight. ... Events January - Book by Maria Monk claims that she was sexually exploited in a Canadian convent February 3 - United States Whig Party holds its first convention in Albany, New York. ... 1839 was a common year starting on Tuesday (see link for calendar). ... Illustration of John Ericsson John Ericsson (July 31, 1803 – March 8, 1889) was a Swedish inventor and mechanical engineer, as was his brother, Nils Ericson. ... This article describes the ship the Great Eastern. ...

In 1848 the British Admiralty held a tug of war contest between a propeller driven ship the Rattler and a paddle wheel ship the Alecto. The propeller won, towing the Alecto stern first at a speed of 2.8 knots, but it was not until the early 20th century that paddle propelled vessels were entirely superseded. The propeller replaced the paddles due to efficiency, compactness, less complex mechanicals and reduced probability of damage. For the international law of the sea, see Admiralty law. ... This article is about the boat propulsion implement, etc. ...

Initial designs owed much to the ordinary screw from which their name derived - early propellers consisted of only two blades and matched in profile the length of a single screw rotation. This design was common, but inventors endlessly experimented with different profiles and greater numbers of blades. The propeller screw design stabilized by the 1880s. This article refers to the threaded fastener. ... Events and Trends Technology Development and commercial production of electric lighting Development and commercial production of gasoline-powered automobile by Karl Benz, Gottlieb Daimler and Maybach First commercial production and sales of phonographs and phonograph recordings. ...

In the early days of steam power for ships, when both paddle wheels and screws were in use, ships were often characterized by their type of propellers, leading to terms like screw steamer or screw sloop. Submariners call the propellers on submarines "screws". A steam engine is a heat engine that makes use of the potential energy that exists as pressure in steam, converting it to mechanical work. ... A paddle steamer, paddleboat, or paddlewheeler is a ship driven by one or more paddle wheels driven by a steam engine. ... A screw sloop is a propeller-driven sloop-of-war. ...

Propellers are referred to as "lift" devices, while paddles are "drag" devices.

Cavitation can happen if a propeller turns too fast in the water, with a resultant waste of energy and excessive noise production. (See also fluid dynamics) Cavitation is the phenomenon where small cavities of partial vacuum form in fluid, then rapidly collapse, producing a sharp sound. ... This article or section should be merged with Fluid mechanics Fluid dynamics is the study of fluids (liquids and gases) in motion, and the effect of the fluid motion on fluid boundaries, such as solid containers or other fluids. ...

History

The first screw propellor to be added to an engine was done so by James Watt in Birmingham, England. It was applied to his Steam engine although the screw propellor in itself can be traced to the time of the Egyptians. This article is about the Scottish engineer and inventor. ... The city from above Centenary Square. ... Royal motto: Dieu et mon droit (French: God and my right) Official language None; English is de facto Capital London Capitals coordinates 51° 30 N, 0° 10 W Largest city London Area  - Total Ranked 1st UK 130,395 km² Population  - Total (2001)  - Density Ranked 1st UK 49,138,831... A steam engine is a heat engine that makes use of the potential energy that exists as pressure in steam, converting it to mechanical work. ... The Arab Republic of Egypt, commonly known as Egypt, (in Arabic: مصر, romanized Mişr or Maşr, in Egyptian dialect) is a republic mostly located in northeastern Africa. ...

The first petrol engine propellor to be fitted to a small boat was done so by Frederick William Lanchester also from Birmingham, England. This was tested in Oxford. Gasoline (or petrol) engine is a type of internal combustion engine which is often used for automobiles, aircraft, small mobile vehicles such as lawnmowers or motorcycles, and outboard motors for boats. ... Frederick William Lanchester (October 23, 1868 - March 8, 1946) was an English polymath and engineer who made important contributions to automotive engineering, aerodynamics and co-invented the field of operations research. ... This article is about the city of Oxford in England. ...

See also

• Impeller

External link

• Aircraft-Info.net - Propeller Aircraft (http://www.aircraft-info.net/aircraft/propellor_aircraft/)