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Calculating the lift created by the wings of Mi-24


AeriaGloria

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   Hello, I am trying to figure out the data for amount of lift created by the wing of the Mi-24. Using lift force calculators that take into account air density, lift coefficient, wing area, and airspeed. 

Wing area is taken from Yefim Gordon’s book on Russian Gunship helicopters, a figure of 6.25 meters squared

Now looking at the LUA, there is a Cy value of .0668. And a Cy Flap value of .35. I did some searching to see in what way is Cy related to CL lift coefficient, and it was hard to tell if it was ED’s chosen term for CL or some relation of CL to AOA slope angle. 
 

Anyways just using Cy in the lift calculation at 260 kmh (normal cruise) ended up with 139 kg, extremely small, and both using Cy Flap and Cy Flap + Cy equaled values less then 10% of max takeoff weight of 11,500 kg. Which is believable, but I expected much higher given the much larger then normal wing and 19 degree incidence angle. 
 

This paper seems to show that in flight testing, at a speed of 260 kmh and weight of 11,500 kg, the rotor is giving about 9,500 kg vertical force in level flight. This is about 17% of the lift generated for level flight, which is much closer to the 20-25% figures often apocryphally/anecdotally thrown around for Mi-24 wing lift compared to total lift. download

   This Embry Riddle paper on compound helicopters analyzed several configuration types, one of them is the S-67 which bears the most similarities to our Mi-24, in a section called “pure lift compound helicopters.” They find that the wing, which is at 8 degrees of incidence, begins to be at negative AOA and produce negative lift once speed increases enough and enough negative pitch angle is needed, thus decreasing performance. At such high speeds. With the Mi-24’s 19 degrees of incidence, and by observing that it never seems to come close to that in level flight all the way up to its 330 kmh top speed, I do not think it would suffer from the same effect. viewcontent.cgi?article=1236&context=edt

Anyways, I don’t know if @Yo-Yo can help as this is your area of expertise, but I would very much appreciate any guidance in being able to figure out the age old adage of if the Mi-24 wing really does produce 20-25% of the lift at normal cruise speeds or other speeds, and wether the Cy numbers in the LUA or any other numbers can be used for it

I was using sites such as these to calculate lift, which gave identical numbers, using the common 1.225 kg per meter cubed figure for dry air density, I see that another site seems to default to 1.2754 kg per meters cubed, but they are close enough to give similar results https://www.ajdesigner.com/phpwinglift/wing_lift_equation_force.php#ajscroll

https://www.vcalc.com/wiki/force+of+lift

Thank you for any help given

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