Ever since I started in helos - some considerable time ago - the use of terms such as Vortex Ring - settling with power and overpitching have been mixed and confused. My understanding is:
Vortex Ring - minimum collective pitch (read minimum power), ROD greater than 200ft/min, IAS less than 20 Kts THEN increasing power but nowhere near full power, just like the final couple hundred feet of a sight picture approach (SPA) - this is the incipient stage. What's happening on the rotor blade - outer section is reaching stalling angle of attack due recirculation of tip vortices effecting relative airflow - inboard section reaching stalling angle of attack due to increasing collective pitch exacerbated by washout - middle section is only bit producing lift - as VR develops (more collectve pitch to try in vain to slow increasing ROD - note engine[s] may not be anywhere near full power and RRPM will still be in the green) the section of blade producing lift reduces even further. Recovery - collective down - reduce angle of attack away from stalling angle - cyclic forward - carry vortices away from disc so that recirculation is minimised.
ROD in fully developed VR well in excess of 5000 ft/min! Obviously takes a bit of height for recovery!
Settling with power/overpitching - sight picture approach/hot/high/heavy - lot of collective - engine(s) topped out - drag being produced by rotor system can no longer be overcome by engine power - blades slow down - cone up - heavy landing at least!
Moral - know your helo's capability backwards - don't venture too far into the VR regime and make the final bit of all SPA's slow and steady.
GAGS
E86