THE EMERGENCY AUTO-ROTATION
ROBINSON 22 - KRAL (RIVERSIDE) - RUNWAY 27
HOW TO LAND A HELICOPTER - WITH NO ENGINE POWER
Autorotation is a condition of helicopter flight during which the main rotor of a helicopter is driven only by aerodynamic forces with no power from the engine. It is a manoeuvre where the engine is disengaged from the main rotor system and the rotor blades are driven solely by the upward flow of air through the rotor. In other words, the engine is no longer supplying power to the main rotor. A vector of the rotor thrust in a helicopter is used to give forward thrust in powered flight; thus, where there is no other source of thrust in a helicopter, it must descend when in autorotation.
Or more simply put - If you're flying in a helicopter and the engine stops, the main rotor blades will continue to spin; by descending rapidly, it forces the rushing air up into the rotor blades and causes them to continue to spin and generate the needed lift (think of a blowing on a pin wheel) - as you near the ground, the pilot pulls back on the cyclic (stick) and gently flares the aircraft to slow the approach speed (like a quickstop, but with no collective) and use last bit of lift from the free-spinning rotor blades to land safely.
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