[QUOTEnever a case that the rotor speed is increased to generate more thrust][/QUOTE]
My first rotary steed was the mighty Gnome-engined Whirlwind (S-55), and delving back into my tech I vaguely remember being told that when they re-engined it from the original piston the RRPM was increased from approx 170 (?) to 220 with no other changes. However, it is back in the mists of time, and it could just as easily have been the Wessex. Whatever, I learned a lot about limited power operations during my 3 years on the Whirlwind, so I hate to imagine how limited it must have been with the piston engine.