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In order to calculate the tip speed ($V_{tip} = ω×R$) of Sikorsky CH-53E Super Stallion, I need to find the rotation speed of the main rotor for the forward flight case. Can someone provide an answer with a reliable source? Also can someone provide the tail rotor RPM too?

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  • $\begingroup$ The blade's tip can't move any faster than the speed of sound, at maximum forward speed. Its airspeed will be tip speed + forward speed. Have you tried calculating it back from that? $\endgroup$
    – Therac
    Mar 30, 2023 at 19:47
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    $\begingroup$ Typically a main rotor's tip speed is around 210m/s. With a radius of 12m this gives an $\omega$ of 17.5 rad/s i.e. 167rpm $\endgroup$
    – sophit
    Mar 30, 2023 at 20:59
  • $\begingroup$ @sophit That's seems rather slow. Most helicopters are in the range of 200-400 RPM. A Bell Huey is 320ish. A 206 is around 400. IIRC a Blackhawk is in the 250 range. $\endgroup$
    – John K
    Mar 30, 2023 at 21:13
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    $\begingroup$ @JohnK: do you have something similar for the CH-53? Anyway if you scale 258rpm from 8 to 12m you get the (estimated) 170rpm of the CH-53. $\endgroup$
    – sophit
    Mar 30, 2023 at 22:58
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    $\begingroup$ Oh crap. When I skimmed over the title originally, "Blackhawk" went into my head, not Stallion. Ooops. Your figure of 167 wasn't that far off. Says here 185 thisdayinaviation.com/tag/sikorsky-ych-53a-sea-stallion $\endgroup$
    – John K
    Mar 31, 2023 at 0:16

2 Answers 2

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It says here 185 RPM and 792 RPM for the A model. For the E model with blades are 1.33 meters longer, you need to drop the rotor RPM to about 170 to keep the same blade tip speed. Note that those are nominal speeds; there will be a green arc RPM +/- range that brackets that value with a minimum and maximum RPM limit.

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    $\begingroup$ That's the value for the CH-53A (aka stallion) which has a different rotor than the E (aka super stallion) version: 11m radius and 6 blades vs. 12m radius and 7 blades. If we scale the rpm value according to the different radius, we get 170rpm that should be the correct value for the E version. @JohnK can you please update the answer? 🖖 $\endgroup$
    – sophit
    Mar 31, 2023 at 7:51
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Sikorsky CH-53E

Main rotor tip speed = 732 ft/sec Main rotor radius = 39.5’ Main rotor rpm = 177

Tail rotor tip speed = 733 ft/sec Tail rotor radius = 10’ Tail rotor rpm = 700

Vtip = (R x RPM) / 9.5493

RPM = (Vtip x 9.5493)/R

Vtip = ft/sec R = Rotor Radius feet RPM = Rotor turns per/min

Ref: Helicopter Performance, Stability, and Control Appendix B and pg.11 by Raymond W. Prouty (Author) ISBN-10 ‏ : ‎ 1575242095 ISBN-13 ‏ : ‎ 978-1575242095 https://vertipedia.vtol.org/biographies/getBiography/biographyID/88

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