PPRuNe Forums - View Single Post - Autorotation
Thread: Autorotation
View Single Post
Old 10th December 2007 | 18:01
  #39 (permalink)  
[email protected]
25 Anniversary
 
Joined: Apr 2000
: ATP+Mil
Posts: 10,959
Likes: 1,814
From: EGDC
I don't think VRS is an issue at the end of a vertical auto to EOL - as you pull pitch you are not inducing a flow down through the rotor, you are simply slowing the rotor down by increasing AoA, producing a burst of rotor thrust and lots of rotor drag - the Relative air flow is still form underneath the disc until you hit the ground. If you had power applied to the rotor then it would be a different matter.

In a steady state vertical auto, rotor thrust equal to aircraft weight is produced (otherwise you would keep accelerating towards the ground) as well as sufficient torque to drive the rotor. At the bottom, that surplus of energy driving the rotors is used instead to augment the rotor thrust (but it doesn't last for long) and reduce RoD (hopefully) for touchdown.

As for hover EOLs I have had the lever raised on me from a 5' hover in a Gazelle as I retarded the throttle and suddenly we were at 8-10 feet with the Nr decaying - I don't think I have ever said/shouted "I have control" so forcefully
crab@SAAvn.co.uk is offline  
Reply