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I was wondering whether there is a "rule of thumb" or some kind of estimate (ideally with a source) that states how heavy a rotor system (blades, swash disk, actuators) typically is as a percentage of the total vehicle mass.

"A typical rotor system weighs between X% and Y% of the total helicopter mass."

Something like that would help me a lot! Is there any estimate like that?

Thanks for your help!

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    $\begingroup$ With the gearbox it's some 25 to 30% of the empty weight. Unfortunately I don't have a reference though. $\endgroup$
    – sophit
    Commented Sep 7, 2023 at 12:01
  • $\begingroup$ Thanks for your comment :) What if the Gearbox is not there? I am thinking of a system that can only do autorotation. Thus, only needs: Rotors, swash-disk, and actuators would suffice, no gearbox is needed. $\endgroup$
    – Clex
    Commented Sep 7, 2023 at 13:14
  • $\begingroup$ I'd say 50:50 more or less. Do you have an autogyro in mind? $\endgroup$
    – sophit
    Commented Sep 7, 2023 at 13:40
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    $\begingroup$ Let's say that a typical EMS helicopter might have a gearbox of some 250kg and blades+rotorhead+pitch links+swashplate of other 250kg. Do not forget that another planet means another Mach and Reynolds number (due to different atmosphere properties) and obviously different weight (due to different gravity) so those estimations might be wrong $\endgroup$
    – sophit
    Commented Sep 7, 2023 at 16:56
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    $\begingroup$ Just out of curiosity: would you use the rotor only for landing? $\endgroup$
    – sophit
    Commented Sep 8, 2023 at 7:24

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Here is a link to the NDARC theory manual. NDARC is a rotorcraft design tool developed by NASA. The final two or three chapters are a bunch of detailed weight models for rotorcraft. It should have everything you could possibly want.

Note that if the atmosphere of this other planet has substantially different density, then these equations won't be appropriate. Higher density means the aero loads are much higher -- this means you can get the same lift from a smaller disk turning more slowly, but it also means the drag (and other) loads are also higher. In an extreme, think about propellers for air vs. propellers for water.

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