Inspired by this question.

My knowledge concerning helicopters is quite limited:

  • what is auto-rotation?
  • are there other "rotations" possible?
  • in what do they differ?
  • $\begingroup$ en.wikipedia.org/wiki/Autorotation $\endgroup$ – Simon Apr 11 '14 at 22:10
  • $\begingroup$ the "duplicate" question, while ultimately ending at the same answer, is nowhere near the same question. $\endgroup$ – Erich Mar 23 '15 at 13:00

When a helicopter engine fails, the pilot lets the rotor blade rotate freely pushed by the wind as the helicopter is falling out of the sky. This is called auto-rotation.

Normal rotation is with the engine powering the rotor.

The most important goal of auto-rotation is to get enough lift right before touch down by flaring so the landing is not a crash.

You would also enter into autorotation when the tail rotor becomes ineffective and you can't recover it otherwise. Once the tail rotor is back into action you can drive the rotor again.

  • $\begingroup$ so the crash isn't as bad - what leads you to believe that autorotation leads to a crash? I've done many autorotations and have not crashed yet! $\endgroup$ – Simon Apr 11 '14 at 22:08
  • 1
    $\begingroup$ I'll be more direct. A properly execute auto results in a perfectly controlled, safe touch down. isn't as bad means nothing ;) $\endgroup$ – Simon Apr 11 '14 at 22:23
  • $\begingroup$ @Simon if you know so much why not make your own answer :) $\endgroup$ – ratchet freak Apr 11 '14 at 22:25
  • $\begingroup$ @Simon how many autos have you done to a full touchdown? I'd guess not many as in training they're usually only executed to the flare and then power is rolled back in. That extra couple feet is a big deal... PPL training goals are to survive the landing, not to grease the touchdown. $\endgroup$ – TypeIA Apr 11 '14 at 22:30
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    $\begingroup$ @ratchetfreak why not make your own answer because you've pretty much summed it up. I just took exception to the "crash" assertion. The point I was trying to make, and encouraging you to edit your answer, is that in many types, autos are almost no-events. A bit frisky in low interia types but quite relaxed affairs in something like a 206. $\endgroup$ – Simon Apr 11 '14 at 22:34

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