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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.
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 ...
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 ...
Even when hovering, the rotor tips may be travelling at a significant fraction of the speed of sound. As the helicopter accelerates, its overall speed is added to that of the tips, meaning that the blades on the forward-moving side of the rotor sees significantly higher airspeed than the rearward-moving side, causing a dissymmetry of lift.
Investigators are intensifying their search into what caused the collision between American Airlines Flight 5342 and an Army Black Hawk helicopter, with recovery crews still working to pull ...
The military helicopter that collided with the plane was an Army-piloted Black Hawk on a "routine training flight," said Joint Task Force-National Capitol Region media chief Heather Chairez.
Wednesday's deadly collision between an American Airlines flight and an Army Black Hawk helicopter at Reagan Washington National Airport (DCA) shares striking similarities to a crash that happened ...