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Rotorcraft Flying Menu >Aerodynamics
of Flight >Autorotation
> Autorotation (Forward Flight)
Autorotative force in forward flight is produced
in exactly the same manner as when the helicopter is descending
vertically in still air. However, because for-ward speed changes
the inflow of air up through the rotor disc, all three regions
move outboard along the blade span on the retreating side of
the disc where angle of attack is larger, as shown in figure
3-23. With lower angles of attack on the advancing side blade,
more of that blade falls in the driven region. On the retreating
side, more of the blade is in the stall region. A small section
near the root experiences a reversed flow, there-fore the size
of the driven region on the retreating side is reduced.
Figure 3-23. Blade regions in forward
autorotation descent.
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