# What is the main and tail rotor speed (RPM) for a Sikorsky S52?

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.

• It's variable depending on engine speed... Do you want the range? Should be easy to figure out if you have the gearbox ratios. Sep 2, 2020 at 0:33
• 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. Sep 5, 2020 at 0:13

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.