I'm sure that we had them in the Whirlwind, and that's going back even further
helimutt: Shhhh, don't let anyone else know
__________________
Yes, the Whirlwind had a rotor brake. A cable operated brake band worked on an external drum. very much like a washing machine brake.
The S-76 has a very good, powerful rotor brake. It can be used to stop the rotors with both engines running at idle or stopped (one stopped and the other at idle in the case of the B model only). Both engines can be started with the rotor brake applied. This makes for a very rapid rotor start, useful in the case of high winds. It's applied by one pump of the handle to prime the system then more pumps to apply increasing pressure; a relief valve acts a limiter.
The original electric rotor brake can only be described as
brutal!
The RFM states that the max operating rpm for rotor brake application, both engines stopped, in an emergency, is 107% Nr!