Does anyone know if RHP (assumed to be rotor horse power) is equivalent to SHP (shaft HP)?
This answer is somewhat speculative, but I have strong grounds for the speculations, pls read through:
I've only ever seen bhp used as hp measured directly at engine output shaft, although by definition bhp can be measured at any location of the driveline:
Wikipedia: brake horsepower
In the particular case in question, I strongly believe the reason for the use of the obscure &quot;Rhp&quot; is the unusual way the powertransfer is arranged in this contraption: there is/seems to be no mechanical connection between the actual engine and the rotor. The rotor is actuated pneumatically by jets at the tips of the rotor blades.
There would be no point in measuring the brake horsepower or shaft horsepower of the actual engine due to &quot;weird&quot; power delivery.
It is therefore most likely the hp is measured at rotor hub, but since the rotor in this case sort of &quot;is the engine itself&quot;, to avoid confusion, Rhp is used to declare power. The declared Rhp probably is shaft horsepower. Kinda confusing though :)
Note: several sources list rhp (with some variation in caps) to mean &quot;rated horsepower, which according to Merriam Webster means &quot;the maximum power an airplane engine can develop without failure when operated continuously or for a specified long period under specified conditions&quot;. Even with this definition, I think in this case it refers to hp measured at rotor shaft, produced by the tip jets.