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This question already has an answer here:

Imagine the rotor of a helicopter is not spinning anymore, can you control the aircraft to land safely?

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marked as duplicate by Him, Community Mar 5 '16 at 1:17

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  • $\begingroup$ To answer your question directly, if the rotor is not spinning, then no. You will crash. I suspect that's not what you meant though. If the engine stops, this does not mean that the rotor stops. As long as the rotor is spinning, in the correct range of RPM, then yes, you can fly safely. $\endgroup$ – Simon Mar 5 '16 at 9:49
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    $\begingroup$ Like the propellor on an airplane, the rotor is actually not there for lift or propulsion, it is for keeping the pilot cool. You should see him sweat when that thing stops turning...! $\endgroup$ – McGafter Mar 22 '16 at 10:40
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You're asking two different questions, actually.

  • If the engines fails in a helicopter, the rotor will usually rotate and the pilot can land the helicopter by autorotation. The record is from an altitude of more than 12km by Jean Boulet when he descended via autorotation as the engine flamed out and couldn't be restarted.

  • If the rotor seizes for some reason in a helicopter, there is no lift produced and it will fall down. For tilt rotors like V-22, if the conditions permit (if it is in aircraft mode), the aircraft can be glided like normal fixed wing aircraft.

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Helicopter can land via autorotation. enter image description here

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    $\begingroup$ This is a bad diagram. You do not dive to maintain speed and rotor RPM. $\endgroup$ – Simon Mar 5 '16 at 10:02
  • $\begingroup$ @Simon so what do you do to maintain speed on the rotor? $\endgroup$ – kepler22b Mar 5 '16 at 13:47
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    $\begingroup$ @kepler22b Initially, you lower the collective, to remove the pitch and therefore the drag, then flare to cause the blades to cone and increase the speed of the disc. After that, you fly normally, albeit with a high rate of descent, until the flare at the bottom. During the main part of the auto, you control speed with attitude, just as in normal flight, and control rate of descent with speed. If you dive, the rotor speed decays. If you dive at the point where the engine quits, you can get into big trouble quickly. Lever down, nose up. $\endgroup$ – Simon Mar 5 '16 at 16:19
  • $\begingroup$ to maintain the speed of the rotor, you maintain slightly aft cyclic so that he forward motion of the copter goes up through the driving part of the blade. $\endgroup$ – rbp Mar 17 '16 at 15:00

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