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Russia accidentally leaks image of high speed rotorcraft
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https://cimg6.ibsrv.net/gimg/pprune....5ac8cf2b64.jpg
https://cimg4.ibsrv.net/gimg/pprune....01d9b7d71a.jpg Two seat, internal weapons bays, retractable gear, shrouded rotor heads, fairly LO? |
Why is it that apart from the Kaman Husky, western helos have not adopted the coaxial rotor systems favoured by the Russians?
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G. Andreyvich* OKB at its finest.
* That would be "Gerry Anderson". |
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It's not going to be LO with contra rotating rotors.
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@57mm, Kaman system isn't coaxial.
https://cimg3.ibsrv.net/gimg/pprune....7c0038e27e.jpg For US coaxial, see Sikorsky X-2, S-97 Raider and Sikorsky-Boeing SB>1 Defiant. |
Assymetric length blades? Does the coax drive sort out the out of balance forces that would result?
Looks like they have stolen the Americans AIRWOLF programme design... |
I always thought that blade tip speed was a limiting factor. Relative to airflow, advancing tip goes supersonic, retreating blade stalls, or simething like that. How does this design overcome that law of aerodynamics to achieve such a speed? Or is it relying on the stubby wing and jet propulsion, with freewheeling rotor blades, in high-speed cruise? |
Blade tip speed is of consequence only in high speed forward flight.
Co-axial systems are not an attempt to overcome that problem. It's a problem with all helicopters. |
Originally Posted by dook
(Post 10294783)
Blade tip speed is of consequence only in high speed.forward flight.
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@VinRouge, the blades are the same length. They look shorter in the side view because there are 3 blades to each head.
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How fast is this thing supposed to go |
Originally Posted by dook
(Post 10294806)
I reckon it has a system to stop the blades and move them to a suitable position.
Reduce to c. 150 kts, unwrap rotor blades, apply power, grasp collective, take up wallpaper-hanging in retirement! :) |
Maybe disconnect blades drop collective all the way and then where would the blades rest ?
Any more ideas ? |
I am bereft of ideas. I defer to those such as you who have done transitions!! Do you have helipopter time? I was only PPL! |
I have no helicopter time, only fast jet time, but have learnt a bit by doing technical illustrations for a coupe of manuals on the subject, one written and published by a frequent PPRuNe contributor.
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With the coaxial set-up, the retreating blade doesn't have to produce any lift, so it can relax a bit. With a normal helicopter, where the advancing blade can produce 7 x more lift than the retreating side, it has to throw away that extra lift and only develop as much as the poor old retreating blade is struggling to provide.
Coaxially, the advancing blade can produce as much as it wants, and let the retreater have an easier life. |
Thanks, A C. That helps me understand much better.
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I would also think with the coaxial setup having two sets of blades, you could reduce the diameter thereby reducing the blade tip speed.
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