Sub-ideal Autorotation in Rotorcraft I have another AuRo question for you.
When a Helicopter autorotates (ideally) it is in the turbulent wake state and there is virtually no flow through the rotor disk (figure of Leishman attached). Now, when Vc (descent speed) is roughly -1.8 times vh (induced velocity at hover) the vehicle is considered to autorotate ideally.
What if we do not autorotate ideally? Does the vehicle still have to be in turbulent wake state?
The real question: Is autorotation (and thereby maintaining of an ideal rotor rotation speed) possible in the windmill break state?
For instance, in the work of Dalamagkidis the OHA58 (Chapter 5.1.1) and the Raptor30v2 (Chapter 5.3.1) do not seem to be in turbulent wake state.
As for my calculations, vc/vh was always slightly lower than -2.
However, the vehicles seem to perform well and land softly.
So is the windmill break state a legitimate state for &quot;autorotation&quot;?
Thanks for helping me out! :)
Autorotation in helicopters is rarely ideal, with net rotor torque = 0, because some energy is drained from the turning blades to feed the tail rotor.
There's, however, a continuum between the ideal 'autorotation' and the 'windmill brake state/moulinet frein'. The 'point of ideal autorotation' should be taken as the 'point of minimum'. For any increase of the load (the weight of the gyro, for instance), from that point on, there's a multitude of possible equilibrium points in autorotation along that curve of 'windmill brake state'. Real-word autorotation is always in one of those points, and never at the 'point of ideal autorotation'...  You may find useful this illustration and text. Source included.