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Can helicopters descend vertically?
Vertical, or near-vertical, descent in a helicopter is dangerous. The rotors produce lift by accelerating air downwards – but if you descend vertically, then you’re in that column of downward-moving air, trying to fly in the downdraft of your own rotors. The technical term is “vortex ring state”.
What is autorotation in a helicopter?
Autorotation. In a helicopter, an autorotative descent is a power-off maneuver in which the engine is disengaged from the main rotor disk and the rotor blades are driven solely by the upward flow of air through the rotor. [Figure 11-1] In other words, the engine is no longer supplying power to the main rotor.
What happens if a helicopter engine stops?
If the helicopter engine stops, everything will go quiet in the cockpit, and the machine will yaw violently to one side. When this happens, the pilot needs to instantly lower the collective, taking the pitch off the rotor blades, and initiating a descent.
When does autorotation take place in a helicopter?
Autorotation can take place straight downwards in vertical flight, but the general recommendation is to maintain forward speed, like a fixed wing gliding: the rate of descent is much lower if there is forward speed. Image source. We associate helicopters with hovering, but this is a strenuous effort.
Which is better a parachute or vertical autorotation?
So in vertical descent, the auto-rotating rotor is almost as good as a parachute of the same area – it’s just that the parachute size is a bit small for the typical payload of a helicopter, resulting in vertical descent speeds of between 3,600 to 6,200 ft/min. By way of comparison:
Why is forward speed not used in autorotation?
During autorotation, forward speed is used to control rotor head speed. In auto, the engine is disconnected (in the case of tail rotor failure) or just plain dead, so it can’t be used to control rotor speed.