Mi-24 rotor washout? [SOLVED]

[AeriaGloria]

  Anyone know what the washout on the Mi-24 rotor is? The twist from root to tip? On Mi-8 I believe it is 5 degrees. On Mi-35M about 7.2 degrees. There has to be some amount on Mi-24, and a small amount can be seen in real life pictures. You can see it modeled in the DCS AH-64. 
 

If anyone knows, I would be very interested 

EDIT: Not sure I can delete the thread but might as well keep it up if anyone else is interested. Have been translating a technical/maintenance manual for Mi-24D/V. 

Now, when I said Mi-8 has 5 degrees of twist, what it actually is is the first 20% of the rotor is 5 degrees up, and after 20% of the rotor length it steadily changes until it is 0 degrees at the tip. 
 

  It is same for Mi-24D/V/P except that it is only 3.5 degrees for the first quarter of the blade, then changes linearly after that until the tip is 0 degrees. This is why at even 1 degree collective there can be significant lift. And the use of this twist/washout is to even out the lift generated across the rotor, as well as allowing portions of the wing to remain unstalled if the center stalls, such as in autorotation or high AOA maneuvers. During autorotation having this twist allows different parts of the rotor to be at different AOA, increasing the efficiency of the section around the center that provides lift in autorotation

In aircraft wings, this helps reduce the severity of stalling, instead of it happening all at once it happens gradually starting at the root. And since the stall happens at the root with the tips being a lower angle and less/not stalled, you still have airflow over the ailerons allowing control. This also increases directional stability 

This gradual stalling likely also helps our helicopters, during RBS and high alpha/mushing. During mushing maneuvers you notice this in other helcipters, but in the Mi-24 is harder to notice as almost any positive AOA causes the wing to stall, which causes a rapid pitch up, since the wing is behind the center of gravity and creating a pitch down force that goes away after stalling. This increas in alpha as the stalled wing makes the helicopter rapid pitch up completely stalls the rotor. But this washout probably makes it easier to control and recover. You can hear the rotors begin to slap and start to stall sometimes(which is slow and gradual thanks to washout, even if it is less then other helos), and can use that to “ride the edge” of the maneuver limit where the wing is at maximum AOA without stalling 
 

Thank you for coming to my aerodynamical TED talk
 

Edited May 18, 2022 by AeriaGloria