What causes a helicopter to lift?
In the case of a helicopter, the object is the rotor blade (airfoil) and the fluid is the air. Lift is produced when a mass of air is deflected, and it always acts perpendicular to the resultant relative wind. A symmetric airfoil must have a positive AOA to generate positive lift. At a zero AOA, no lift is generated.
What is meant by dissymmetry of lift?
Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters and autogyros in forward flight.
What design features help compensate for dissymmetry of lift in helicopter tail rotors?
The horizontal hinge, called the flapping hinge, allows the blade to move up and down. This movement is called flapping and is designed to compensate for dissymmetry of lift. The flapping hinge may be located at varying distances from the rotor hub, and there may be more than one hinge.
What are Dissymmetric molecules?
Dissymmetric molecules: Molecule will be a dissymmetric molecule if it has no plane of symmetry, no centre of symmetry and no alternating axis of symmetry. Asymmetric molecules: Dissymmetric molecule having at least one asymmetric carbon is known as asymmetric molecule.
What is the purpose of tail rotor in helicopter?
A helicopter tail rotor serves two essential functions. It provides a counteracting force to the helicopter’s main rotor; without the sideways thrust produced by the tail rotor, the torque generated by the main rotor would spin the helicopter’s body in the opposite direction.
What are the four principles of aerodynamics?
The four forces of flight are lift, weight, thrust and drag. These forces make an object move up and down, and faster or slower.
What is dissymmetry of lift?
Dissymmetry of lift is the unequal rotor thrust, or lift, produced by the rotor disc due to forward flight or wind. With forward flight, one blade is advancing into the wind while the other blade is retreating, or going with the wind.
Why does the tail rotor experience dissymmetry of lift?
The tail rotor experiences dissymmetry of lift during forward flight, because it also has advancing and retreating blades. Dissymmetry is corrected for by a flapping hinge action. Two basic types of flapping hinges, the delta and the offset hinge, are used on most contemporary helicopters.
What is the lift differential on a helicopter?
Since lift increases as the square of the airspeed, a potential lift variation exists between the advancing and retreating sides of the rotor disk. This lift differential must be compensated for, or the helicopter would not be controllable.