# Can a helicopter enter Vortex Ring State In Auto Rotation? [see qualifiers]

If you are in a vertical descent [no wind] with rotor at max RPM Auto, and you abruptly pull full collective, the momentum of the blades will drive air down creating down wash.

Now obviously this is a totally hypothetical question with no real world use, but, presuming a high enough inertia rotor system, in this very specific scenario is it possible to at least enter the incipient phase of VRS? [before the rotor folded and you fell to your death]

Please no answers just saying you go into auto to get out of VRS, I am looking for a very specific yes or no.

• Seems to be very well answered already here: aviation.stackexchange.com/questions/43028/…. Essentially, you cannot get VRS in autorotation, because in autorotation you are falling and leaving the downwash behind, above the rotors. May 29 '18 at 11:34
• Autorrotation and VRS are very distinct and incompatible states of the rotor. The answer is no unless you add enough qualifiers to make one of the two states unrecognisable (and thus no longer aptly named) May 29 '18 at 11:43
• Are you actually trying to ask "Is it possible to enter VRS from autorotation, without engine power?" to which I suspect this comment may be helpful (although I believe it deserves its own answer here by a more knowledgeable person than me). May 29 '18 at 12:28
• That's not what he's asking. He's asking if VRS can be induced in the brief interval where you exit autorotation by pulling pitch, as in the post-flare landing phase, in some hypothetical helicopter that had oodles and oodles of rotor inertia. Not a totally loopy question. A UH-1 can lift off the ground, do a 360 degree pedal turn, and set down again on rotor inertia alone if the rotor rpm is at the top of the green arc when it's started. So the question is how much time does it take to get a VRS going in a vertical descent under power (VRS and SWP are two different things). May 29 '18 at 13:08
• Possible duplicate of Why is vortex state impossible in autorotation? May 29 '18 at 23:27