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Some Clarifications





Some Clarifications  

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Author: B. Real   Date: 4/30/2022 7:31:22 PM  +4/-5   Show Orig. Msg (this window) Or  In New Window

To expand a little on my initial post... SWP and VRS are different. VRS is *always* SWP, but the reverse is not always true. By definition, Vortex Ring State is when your rotor is re-ingesting its own downwash - I think Olderndirt called it "cavitating," which is close enough. That's not necessarily the case with SWP, which may just be that more power is requied than is available (from either the engine *or* the rotor). For example, let's say that you're heavy on a high-DA, relatively calm day - if you come in with a little too much vertical speed you might not have enough "oomph" in the rotor system to stop the descent. The ship settles right through your ground cushion and you end up with smiling skids and a frowning owner. Sorry, this was not a VRS encounter, so don't blame it on that, Robbie boys!


For VRS to occur, you not only have to be below ETL, but the hovering helicopter has to be stationary over the column of air it is producing. *ANY* lateral movement of the aircraft or that downwash will inhibit or cancel out that re-ingestion. This is why Claude's method works so well - use the tail rotor thrust to "blow" the helicopter sideways and out into clean air. You don't even have to get the rotor up through ETL again - just get it moving (sideways, in this case) with respect to your downwash. Claude may not have invented this manuever or the technique, but at least he showed us how easy it is to get *out* of VRS if you're dumb enough to get into it in the first place.


In a steep, slow, *downwind* approach in which the wind velocity matches your forward speed, you won't be outrunning your downwash. Do the same approach into even a light wind and your downwash will be left behind and voila! (as Claude would say) no VRS. So yes, wind *is* important when it comes to getting into ...and out of...VRS.  With SWP or VRS, since they usually happen at the bottom of messed-up approaches, by the time you recognize that you're getting into it, it's probably too late.

 
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VRS Practice/Demonstration +5/-3 B. Real 4/30/2022 10:09:57 AM