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I have read that if helicopter's engine fails, you set the pitch to minimum but not reverse pitch. The rotor would have to be tilted back to provide an angle of attack on the blades so it glides like a fixed wing aircraft but with the rotor spinning to keep the blades from buckling under the weight of the craft. I think it would have to go into a slight reverse pitch to spin the same way. That would also provide more angle of attack on the receding blades where it is needed because of the lower air speed over those blades. How does it keep rotating in the same direction with the air going up through it if it can't go into a slight reverse pitch?

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  • $\begingroup$ "If helicopter's rotor blades can't go into a slight reverse pitch..." en.wikipedia.org/wiki/Autorotation Does not mention "negative" pitch or "reverse" pitch, but refers in several places to "lowering the pitch angle." $\endgroup$ Nov 13, 2023 at 12:41
  • $\begingroup$ @Solomon Slow I had a look at that wikipedia site. It doesn't mention anything about pitch in the section about autorotation. I am very sceptical of what they call minimum pitch. I think it would have to be a slight reverse pitch. That would drive the rotor in the same direction, and provide the extra angle of attack on the receding side, and less on the advancing side where the blades are going into the oncoming air. Unless there is some really wierd aerodynamic effect on the blades, I cannot see how it could work without reverse pitch until you are pulling up to land. $\endgroup$ Nov 15, 2023 at 13:41
  • $\begingroup$ OK, The essense of your question is, "How can a helicopter autorotate without putting at least some portion of the blades during some portion of the cycle into reverse pitch?" But, what reason do you have to think that the pilot is not able to do exactly that? $\endgroup$ Nov 15, 2023 at 13:54
  • $\begingroup$ P.S., Maybe you would have better luck getting somebody to answer to your question (I don't know how to answer it) if you moved it to the Aviation StackExchange site. $\endgroup$ Nov 15, 2023 at 14:12
  • $\begingroup$ @Solomon On this site, but I can't remember where, I came across somebody who thought axactly the same as me, and asked if the pitch is reversed during autorotation. The answer he got said no, and illustrated it with a diagram that looked more like powered flight. I think he might have got it wrong. The pitch is probably slightly negative. Thanks for your help. $\endgroup$ Nov 15, 2023 at 23:42

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