I need the RPMs for the main and tail rotor of a Sikorsky S52 for the research I am doing for my degree. I tried checking flight manuals and other websites, but I don't find concrete numbers, only percentage values.

  • $\begingroup$ It's variable depending on engine speed... Do you want the range? Should be easy to figure out if you have the gearbox ratios. $\endgroup$
    – Ron Beyer
    Sep 2, 2020 at 0:33
  • 1
    $\begingroup$ I can't find anything after a quick google, but if you reached out to a museum with your question you may be able get a good answer, old guys like to talk about stuff like this, just a matter of getting the right person. $\endgroup$ Sep 5, 2020 at 0:13

1 Answer 1


Given the $5m$ main rotor radius and the typical blade's tip speed due to the rotation around the hub of some $200m/s$, this gives:

$ \omega = v_{tip} / r = 200/5 = 40 [rad/s] = 380rpm $

For the tail rotor this is proportionally bigger and equals $1900rpm$.

It could be that due to the technological limitations of those times, the $\omega$ was actually a bit lower but in absence of concrete numbers, these should be reasonable values to start with.

  • $\begingroup$ Wikipedia states the max speed as 180 km/h, which should be included in the tip speed calculation. $\endgroup$
    – Koyovis
    Aug 7 at 22:16
  • $\begingroup$ The OP asks for a definit source, not an assumption $\endgroup$
    – U_flow
    Aug 8 at 5:56
  • $\begingroup$ I updated the answer with the previous comments $\endgroup$
    – sophit
    Aug 8 at 6:25

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