Scimitar propeller

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Swept propeller Swept-propeller7.svg
Swept propeller
Scimitar propeller on a 1926 Alexander Eaglerock 1926 Alexander Eaglerock NC2568.jpg
Scimitar propeller on a 1926 Alexander Eaglerock
Eight-blade scimitar propellers on the Airbus A400M Atlas Airbus A400M Rollout.JPG
Eight-blade scimitar propellers on the Airbus A400M Atlas

A scimitar propeller is a type of propeller that has curved blades with increasing sweep along the leading edge. Their name is derived from their visual similarity to the curved blades of scimitars. In the early 1900s, as established by the French aeronautical inventor Lucien Chauvière and his commercial success with his scimitar-shaped Integrale propeller design, [1] they were made of laminated wood. The combination of light weight and efficient aerodynamics results in more power and reduced noise.[ citation needed ]

All propellers lose efficiency at high rotational speeds due to an effect known as wave drag, which occurs as an airfoil approaches supersonic speeds. This powerful form of drag reduces propeller efficiency at high rotational speed which, in turn, reduces power transmission from the aircraft's engine. [2] In the case of a propeller, this effect can happen when the propeller turns fast enough that the tips of the blades approach the speed of sound, even if the plane itself is not moving forward. Wave drag also occurs at high linear aircraft speeds. [2] According to the same principles that govern swept wings in high-speed aircraft, propeller blades can be swept back in order to mitigate wave drag, thus allowing them to remain efficient at higher rotational speeds. Since the inboard part of a propeller has a slower rotational velocity relative to the tip, the blade becomes progressively more swept from the propeller hub to the tip, giving rise to its characteristic shape.

In the 1940s, NACA started researching swept propellers for use in high-speed propeller-driven aircraft. [3] Modern usage of scimitar propellers centers around turboprop and propfan engines. Since these forms of propulsion are capable of driving a propeller at transsonic or supersonic rotational speeds, as well as propelling aircraft to similarly high speeds, mitigation of wave drag is an important consideration in achieving high aerodynamic efficiency. Like modern straight-bladed propellers, scimitar propellers often make use of lightweight materials to further increase efficiency.

Propfan engines were intended to deliver significant improvements in fuel economy compared to contemporary turbofan engines, and in this they succeeded. In static and air tests on a modified DC-9, propfans reached a 30% improvement.[ citation needed ] This efficiency comes at a price, as one of the major problems with the propfan is noise, particularly in an era where aircraft are required to comply with increasingly strict EASA and FAA noise requirements for certification. Propfans often feature scimitar blades as they typically operate at high rotational speeds.

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Flying wing Tailless fixed-wing aircraft that has no definite fuselage

A flying wing is a tailless fixed-wing aircraft that has no definite fuselage, with its crew, payload, fuel, and equipment housed inside the main wing structure. A flying wing may have various small protuberances such as pods, nacelles, blisters, booms, or vertical stabilizers.

Supersonic transport Type of commercial airliner (SST)

A supersonic transport (SST) or a supersonic airliner is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. To date, the only SSTs to see regular service have been Concorde and the Tupolev Tu-144. The last passenger flight of the Tu-144 was in June 1978 and it was last flown in 1999 by NASA. Concorde's last commercial flight was in October 2003, with a November 26, 2003 ferry flight being its last airborne operation. Following the permanent cessation of flying by Concorde, there are no remaining SSTs in commercial service. Several companies have each proposed a supersonic business jet, which may bring supersonic transport back again.

Swept wing Plane wing that angles backwards or forwards

A swept wing is a wing that angles either backward or occasionally forward from its root rather than in a straight sideways direction.

In aeronautics, wave drag is a component of the aerodynamic drag on aircraft wings and fuselage, propeller blade tips and projectiles moving at transonic and supersonic speeds, due to the presence of shock waves. Wave drag is independent of viscous effects, and tends to present itself as a sudden and dramatic increase in drag as the vehicle increases speed to the critical Mach number. It is the sudden and dramatic rise of wave drag that leads to the concept of a sound barrier.

Wingtip device Aircraft component fixed to the end of the wings to improve performance

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Ducted fan Air moving arrangement

In aeronautics, a ducted fan is a thrust-generating mechanical fan or propeller mounted within a cylindrical duct or shroud. Other terms include ducted propeller or shrouded propeller. When used in vertical takeoff and landing (VTOL) applications it is also known as a shrouded rotor.

Propfan Type of aircraft engine

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Airplane Powered, flying vehicle with wings

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Wing tip Part of an aircraft

A wing tip is the part of the wing that is most distant from the fuselage of a fixed-wing aircraft.

Oblique wing

An oblique wing is a variable geometry wing concept. On an aircraft so equipped, the wing is designed to rotate on center pivot, so that one tip is swept forward while the opposite tip is swept aft. By changing its sweep angle in this way, drag can be reduced at high speed without sacrificing low speed performance. This is a variation on the classic swing-wing design, intended to simplify construction and retain the center of gravity as the sweep angle is changed.

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Geared turbofan Turbofan engine with a gearbox used to drive its fan

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An airbreathing jet engine is a jet engine that ejects a propelling (reaction) jet of hot exhaust gases after first taking in atmospheric air, followed by compression, heating and expansion back to atmospheric pressure through a nozzle. Alternatively the reaction jet may include a cold jet of ducted bypass air which has been compressed by a fan before returning to atmospheric pressure through an additional nozzle. These engines are gas turbine engines. Engines using only ram for the compression process, and no turbomachinery, are the ramjet and pulsejet.

Fuel economy in aircraft Aircraft fuel efficiency

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Cyclorotor Perpendicular axis marine propulsion system

A cyclorotor, cycloidal rotor, cycloidal propeller or cyclogiro, is a fluid propulsion device that converts shaft power into the acceleration of a fluid using a rotating axis perpendicular to the direction of fluid motion. It uses several blades with a spanwise axis parallel to the axis of rotation and perpendicular to the direction of fluid motion. These blades are cyclically pitched twice per revolution to produce force in any direction normal to the axis of rotation. Cyclorotors are used for propulsion, lift, and control on air and water vehicles. An aircraft using cyclorotors as the primary source of lift, propulsion, and control is known as a cyclogyro or cyclocopter. A unique aspect is that it can change the magnitude and direction of thrust without the need of tilting any aircraft structures. The patented application, used on ships with particular actuation mechanisms both mechanical or hydraulic, is named after German company Voith Turbo.

Thickness-to-chord ratio Ratio in aeronautics

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  1. Gibbs-Smith, C.H. (2003). Aviation. London: NMSO. p. 150. ISBN   1-9007-4752-9.
  2. 1 2 Gudmundsson, Snorri (2022). General Aviation Aircraft Design (Second Edition). Butterworth-Heinemann. p. 597-656. ISBN   978-0-12-818465-3.
  3. Whitcombe, Richard (May 4, 1950). A description of the design of highly swept propeller blades. Langley Aeronautical Laboratory.