Information about Helicopter Rotor
A rotor is the rotating part of a helicopter which generates lift, either vertically in the case of a main rotor, or horizontally in the case of a tail rotor.
In the 1930s, Arthur Young improved stability of two bladed rotor systems with the introduction of a stabilizer bar. This system was used in several Bell and Hiller helicopter models. It is also used in many remote control model helicopters.
Most modern helicopters employ a rigid rotor design, in which flexible materials are used in place of hinges.
The simple rotor of a Robinson R22 showing (from the top):
The pitch of main rotor blades is varied throughout its rotation in order to control the magnitude and direction of the thrust vector. Collective pitch is used to increase or decrease rotor thrust perpendicular to the axis of rotation. Collective pitch controls the magnitude of the thrust vector. Blade pitch is varied during rotation to effectively tilt the rotor disk and control the direction of the thrust vector. These blade pitch variations are controlled by the swash plate.
The swash plate is two concentric disks or plates, one plate rotates with the blades while the other does not rotate. The rotating plate is connected to individual blades through pitch links and pitch horns. The non-rotating plate is connected to links which are manipulated by pilot controls, specifically, the collective and cyclic controls.
The swash plate can shift vertically and tilt to some degree. Through shifting and tilting, the non-rotating plate controls the rotating plate, which in turn controls the individual blade pitch.
Cierva realized that the advancing blade on one side created greater lift than on the retreating side due to increased airspeed on the advancing side which creates a rolling force. The scale model was constructed with flexible materials, specifically rattan, so the rolling force was absorbed as the blades flapped and compensated for dissymmetry of lift. Cierva concluded that the full size steel rotor hub was far too rigid and introduced flapping hinges at the rotor hub.
Flapping hinges solved the rolling problem, but introduced lateral hub stresses as the blade center of mass moved as the blades flapped. Due to conservation of angular momentum, the blades accelerate and decelerate as their center of mass moves inward and outward, like a twirling ice skater. Cierva added lag-lead, or delta hinges to reduce lateral stresses.
Arthur Young found that stability could be increased significantly with the addition of a stabilizer bar perpendicular to the two blades. The stabilizer bar has weighted ends which cause it to stay relatively stable in the plane of rotation. The stabilizer bar is linked with the swash plate in such a manner as to reduce the pitch rate. Other names are Hiller panels, Hiller-system, Bell-Hiller-system, and flybar. In fly by wire helicopters or RC-models a computer with gyroscopes and a venturi sensor can replace the stabilizer. This flybarless design has the advantage of easy reconfiguration.
The two blades can flap as a unit and therefore do not require lag-lead hinges (the whole rotor slows down an accelerates per turn). Two bladed systems require a single teetering hinge and two coning hinges to permit modest coning of the rotor disk as thrust is increased.
History and development
Before the development of powered helicopters in the mid 20th century, autogiro pioneer Juan de la Cierva researched and developed many of the fundamentals of the rotor. Cierva is credited with successful development of multi-bladed, fully articulated rotor systems. This type of system is widely used today in many multi-bladed helicopters.In the 1930s, Arthur Young improved stability of two bladed rotor systems with the introduction of a stabilizer bar. This system was used in several Bell and Hiller helicopter models. It is also used in many remote control model helicopters.
Most modern helicopters employ a rigid rotor design, in which flexible materials are used in place of hinges.
Rotor head design
The rotor head is a robust hub with attachment points for the blades and mechanical linkages designed to control the pitch of the blades.Parts and functions
)
The simple rotor of a Robinson R22.
The simple rotor of a Robinson R22 showing (from the top):
- The following are driven by the link rods from the rotating part of the swashplate.
- Pitch hinges, allowing the blades to 'twist', ie change pitch or roll.
- Teeter hinge, allowing one blade to rise while the other falls. Usually rise and fall is due to pitch or roll. There may be harmonics, it allows pitch and roll of the rotor to be independent of the fuselage, it disables negative G flights.
- Scissor link and counterweight, carries the main shaft rotation down to the upper swashplate
- Rubber covers protect moving and stationary shafts
- Swashplates, transmitting cyclic and collective pitch to the blades (the top one rotates)
- Three non-rotating control rods transmit pitch information to the lower swashplate
- Main mast leading down to main gearbox
)
An advanced rotor head for a Sikorsky S-92
Swash plate
''Main article: Swashplate (helicopter).The pitch of main rotor blades is varied throughout its rotation in order to control the magnitude and direction of the thrust vector. Collective pitch is used to increase or decrease rotor thrust perpendicular to the axis of rotation. Collective pitch controls the magnitude of the thrust vector. Blade pitch is varied during rotation to effectively tilt the rotor disk and control the direction of the thrust vector. These blade pitch variations are controlled by the swash plate.
The swash plate is two concentric disks or plates, one plate rotates with the blades while the other does not rotate. The rotating plate is connected to individual blades through pitch links and pitch horns. The non-rotating plate is connected to links which are manipulated by pilot controls, specifically, the collective and cyclic controls.
The swash plate can shift vertically and tilt to some degree. Through shifting and tilting, the non-rotating plate controls the rotating plate, which in turn controls the individual blade pitch.
Fully articulated rotors
During the development of the autogyro, Juan de la Cierva built scale models to test his designs. After promising results, he built full size models. Just prior to takeoff, his autogyro rolled unexpectedly and was destroyed. Believing this to have been caused by sudden wind gusts, Cierva rebuilt it only to suffer an almost identical accident. These setbacks caused Cierva to consider why his models flew successfully, while the full-sized aircraft did not.Cierva realized that the advancing blade on one side created greater lift than on the retreating side due to increased airspeed on the advancing side which creates a rolling force. The scale model was constructed with flexible materials, specifically rattan, so the rolling force was absorbed as the blades flapped and compensated for dissymmetry of lift. Cierva concluded that the full size steel rotor hub was far too rigid and introduced flapping hinges at the rotor hub.
Flapping hinges solved the rolling problem, but introduced lateral hub stresses as the blade center of mass moved as the blades flapped. Due to conservation of angular momentum, the blades accelerate and decelerate as their center of mass moves inward and outward, like a twirling ice skater. Cierva added lag-lead, or delta hinges to reduce lateral stresses.
Two bladed rotors
Rotors with more than two blades have two dedicated connections, which make the inner swash plate turn. In two bladed rotor systems the blades take over this task.Arthur Young found that stability could be increased significantly with the addition of a stabilizer bar perpendicular to the two blades. The stabilizer bar has weighted ends which cause it to stay relatively stable in the plane of rotation. The stabilizer bar is linked with the swash plate in such a manner as to reduce the pitch rate. Other names are Hiller panels, Hiller-system, Bell-Hiller-system, and flybar. In fly by wire helicopters or RC-models a computer with gyroscopes and a venturi sensor can replace the stabilizer. This flybarless design has the advantage of easy reconfiguration.
The two blades can flap as a unit and therefore do not require lag-lead hinges (the whole rotor slows down an accelerates per turn). Two bladed systems require a single teetering hinge and two coning hinges to permit modest coning of the rotor disk as thrust is increased.
Tail Rotors
Tail rotors are generally simpler than main rotors since they require only thrust control. A simplified swash plate is used to control collective pitch. Two bladed tail rotors include a teetering hinge to compensate for asymmetry of lift.Blade design
The blades of a helicopter are long, narrow airfoil cross-sections with a high aspect ratio, a shape which minimises drag from tip vortices (see the wings of a glider for comparison). They generally contain a degree of washout to reduce the lift generated at the tips, where the airflow is fastest and vortex generation would be a significant problem. Rotor blades are made out of various materials, including aluminium, composite structure and steel / Titanium erosion shields along the leading edge.Limitations and hazards
Helicopters with semi-rigid rotors, for example the two-bladed design seen on Robinson and some other light helicopters, must not be subjected to a low-g condition. Otherwise their rotors may move beyond the normal limits in a condition known as mast bumping which can cause the rotor droop stops to shear the mast and hence detach the whole system from the aircraft.External Links
helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades. Helicopters are classified as rotorcraft or rotary-wing aircraft to distinguish them from fixed-wing aircraft because the helicopter derives
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The lift force, lifting force or simply lift is a mechanical force generated by solid objects as they move through a fluid.[1]
While many types of objects can generate lift, the most common and familiar object in this category is the airfoil, a
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While many types of objects can generate lift, the most common and familiar object in this category is the airfoil, a
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autogyro is a type of rotorcraft invented by Juan de la Cierva in 1919, making its first successful flight on January 9, 1923 at Cuatro Vientos Airfield in Madrid, Spain.[1] The lift for an autogyro is provided by a rotor, similar to that of a helicopter.
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Juan de la Cierva (21 September 1895 – 9 December 1936) was a Spanish civil engineer and pilot. His most famous accomplishment was the invention in 1919 of the Autogiro, a type of aircraft that later came to be called an autogyro.
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Integral Theory
Integral theorists:
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Integral theorists:
- Clare Graves, Don Beck
- Ken Wilber
- AQAL
- Integral ecology
- Integral politics
- Integral psychology
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Bell Helicopter Textron
Aerospace
Founded 1935
Headquarters Fort Worth, Texas, USA
Products Helicopters, Tiltrotors
Parent Textron
Website bellhelicopter.
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Aerospace
Founded 1935
Headquarters Fort Worth, Texas, USA
Products Helicopters, Tiltrotors
Parent Textron
Website bellhelicopter.
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Type Light utility and trainer helicopter
Manufacturer Robinson Helicopter Company
Designed by Frank Robinson
Maiden flight 1975
Introduced 1979
Number built over 3,600
Unit cost $185,000
Variants Robinson R44
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Manufacturer Robinson Helicopter Company
Designed by Frank Robinson
Maiden flight 1975
Introduced 1979
Number built over 3,600
Unit cost $185,000
Variants Robinson R44
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swashplate is a device that translates the pilot's (or autopilot's) commands via the helicopter flight controls into motion of the main rotor blades. Because the main rotor blades are spinning, the swashplate is used to transmit three of the pilot's commands from the non-rotating
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range of input/output ratios in addition to its infinite number of possible ratios; this qualification for the IVT implies that its range of ratios includes a zero output/input ratio that can be continuously approached from a defined 'higher' ratio.
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swashplate is a device that translates the pilot's (or autopilot's) commands via the helicopter flight controls into motion of the main rotor blades. Because the main rotor blades are spinning, the swashplate is used to transmit three of the pilot's commands from the non-rotating
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spatial vector, or simply vector, is a concept characterized by a magnitude and a direction. A vector can be thought of as an arrow in Euclidean space, drawn from an initial point A pointing to a terminal point B.
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Calameae
Genera
Calamus
Calospatha
Ceratolobus
Daemonorops
Eremospatha
Eugeissonia
Korthalsia
Laccosperma
Metroxylon
Myrialepis
Oncocalamus
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Genera
Calamus
Calospatha
Ceratolobus
Daemonorops
Eremospatha
Eugeissonia
Korthalsia
Laccosperma
Metroxylon
Myrialepis
Oncocalamus
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Dissymmetry of lift in helicopter aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters in lateral flight, whether the direction of flight be forwards, sideways or in reverse.
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angular momentum of an object rotating about some reference point is the measure of the extent to which the object will continue to rotate about that point unless acted upon by an external torque.
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A gyroscope is a device for measuring or maintaining orientation, based on the principle of conservation of angular momentum. The device is a spinning wheel whose axle is free to take any orientation.
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Venturi effect is an example of Bernoulli's principle, in the case of incompressible fluid flow through a tube or pipe with a constriction in it. The fluid velocity must increase through the constriction to satisfy the equation of continuity, while its pressure must decrease due to
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The tail rotor of a helicopter is mounted on the tail of a traditional single-rotor helicopter, close to perpendicular to the main rotor. It is primarily used in order to counteract the yaw motion and the torque that a rapidly turning disk naturally produces.
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airfoil (in American English, or aerofoil in British English) is the shape of a wing or blade (of a propeller, rotor or turbine) or sail as seen in cross-section.
An airfoil shaped body moved through a fluid produces a force perpendicular to the motion called lift.
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An airfoil shaped body moved through a fluid produces a force perpendicular to the motion called lift.
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aspect ratio is an airplane's wing's span divided by its standard mean chord (SMC). It can be calculated more easily as span squared divided by wing area:
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Wingtip vortices are regions of high vorticity which develop at the tip of a wing as it flies through the air (or potentially another fluid). Wingtip vortices are a form of induced drag, an essentially unavoidable side-effect of the wing generating lift.
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Gliders or Sailplanes are heavier-than-air aircraft primarily intended for unpowered flight. See also gliding and motor gliders for more details.[1]
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Terminology
A "glider" is an unpowered aircraft...... Click the link for more information.
Wingtip vortices are regions of high vorticity which develop at the tip of a wing as it flies through the air (or potentially another fluid). Wingtip vortices are a form of induced drag, an essentially unavoidable side-effect of the wing generating lift.
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helicopter is an aircraft which is lifted and propelled by one or more horizontal rotors, each rotor consisting of two or more rotor blades. Helicopters are classified as rotorcraft or rotary-wing aircraft to distinguish them from fixed-wing aircraft because the helicopter derives
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The Robinson Helicopter Company of Torrance, California is the largest manufacturer of civil helicopters in the world.
The company was founded in 1973 by Frank Robinson, an ex-employee of Bell Helicopter and The Hughes Helicopter Company.
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The company was founded in 1973 by Frank Robinson, an ex-employee of Bell Helicopter and The Hughes Helicopter Company.
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Low-g condition is a phase of aerodynamic flight where the airframe is temporarily unloaded. The pilot—and the airframe—feel temporarily "weightless" because the aircraft is in free-fall or decelerating vertically at the top of a climb.
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