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Dissymmetry of lift [1]: 2–20 [2] (also known as asymmetry of lift [3]: 342 [4] or asymmetric lift [5] [6]) in rotorcraft aerodynamics refers to an unequal amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters and autogyros in forward flight.
Dissymmetry of lift is an aerodynamic phenomenon caused by the rotation of a helicopter's rotors in forward flight. Rotor blades provide lift proportional to the amount of air flowing over them. When viewed from above, the rotor blades move in the direction of flight for half of the rotation (advancing half), and then move in the opposite ...
Flapback [1]: 3:28 or blowback [2]: 2–14, 2–20, 2–21 [3] is the tilting of a helicopter rotor disc, usually aft (backwards), which occurs in several circumstances. In normal operating circumstances, forward flight results in flapback caused by dissymmetry of lift and the transverse flow effect.
Overhead view of helicopter rotors. The rotor tips travel much faster than the inner sections, so produce more lift. (For the purposes of this article, the demarcated circular regions are irrelevant and should be ignored.) A helicopter rotor blade is an airfoil, which is driven through the air to create lift. The lift generated is proportional ...
P-factor is extremely significant for helicopters in forward flight, because the propeller disc is almost horizontal. The forward-going blade has a higher airspeed than the backward-going blade, so it produces more lift, known as dissymmetry of lift. Helicopters can control each blade's angle of attack independently (decreasing the angle of ...
Witnesses have revealed what they saw take place at the moment of impact during the horrifying collision between an American Airlines jet and an Army helicopter over the Potomac River. On ...
To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration. A typical helicopter has three flight control inputs: the cyclic stick, the collective lever, and the anti-torque pedals. [2]
Of the 14 helicopter mishaps, 12 occurred during training flights. 2024 "will be a year that Army Aviation looks back on in hopes of never repeating," this month's issue of Flightfax, an Army ...