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S-97 RAIDER first ground testing begins

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posted on Feb, 14 2015 @ 09:06 PM
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Nevermind, I answered my own question.




posted on Feb, 14 2015 @ 10:33 PM
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RBS is a result of high forward air speed of a helicopter. On a single rotor helicopter there will be a blade travelling forward relative to the forward flight of the helicopter. This is referred to as the advancing blade and is 90 degrees to the airframe. On the opposite side, the blade will be travelling backward relative to the forward flight of the helicopter. This is the retreating blade. I hope this is clear so far!

Now, think of the speed of the rotating blades. The air travelling over the blades varies with lower velocities nearer to the hub and the fastest at the blade tips. The outer 30% of the advancing blade is where the most lift is generated and increases with forward speed. On the 70% of the remaining advancing blade, lift will be proportionately less due to slower relative speed as it get closer to the hub. On the opposite side of the helicopter is the retreating blade. This blade moves backward to forward flight (retreating).

In a hover, dynamically the advancing blade and retreating blades are nearly equal in lift. Now, let's start moving forward. For the sake of my explanation, let us assume the advancing blade is on the right and the retreating blade is on the left. At 100 MPH forward speed the advancing blade is generating lift equal to the speed of the rotor RPM and the forward speed. On the other side the retreating blade is generating lift at the rate generated by rotor RPM minus the forward speed. The 70% of the retreating blade closest to the hub is generating nearly no lift. The faster the forward speed the farther out the stalled area goes toward the blade tip. This is retreating blade stall. The helicopter will roll toward the stalled blade.

I hope this helps.



posted on Feb, 15 2015 @ 06:29 AM
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originally posted by: TrueBrit
a reply to: Zaphod58

Wow...

Sounds like a hell of a machine! Little wonder that it looks like such a mean bugger!

I would imagine that in terms of its acceleration to maximum forward speed, it must leave other helicopters standing, what with the tail rotor being angled as it is.

I would love to see a diagram which depicts the various angles at which air is moving through the rotors, and away from them, during maximum forward thrust. Normally, with a chopper which has its nose pointed downward during forward movement, there must be a speed which it would be inadvisable to exceed, because there would be more air moving past the rotor, than being moved BY the rotor, robbing it of purchase on the air around it, and therefore robbing it of lift as well.

This might have something to do with the reason you never see a whacking great pair of jet thrusters on a helicopter?

This design would seem to have far fewer limitations in that regard though!



XH-59A



posted on Feb, 15 2015 @ 07:01 AM
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a reply to: MConnalley

Mind= Blown.

Thanks very much for your previous response, and for posting this image of the XH-59A. I had no idea things had moved on to that point!



posted on Feb, 16 2015 @ 08:56 AM
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a reply to: TrueBrit

The H-59 is a test bed for the ABC theory in the 1970's and '80's. ABC stands for advancing blade concept like the S-97 Raider.



posted on Feb, 17 2015 @ 01:18 AM
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I think Flettner will be laughing harder than Kamov



posted on Feb, 17 2015 @ 09:55 AM
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originally posted by: Blackfinger
I think Flettner will be laughing harder than Kamov

Flettner's helicopter was not a coaxial rotor system. Flettner's first production aircraft was an interleaving system more like the Kamans of the late 1940s and 50s. His next helicopter was the Kolibre a side by side rotor configuration later built by the French after the war.



posted on Feb, 18 2015 @ 07:45 PM
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a reply to: Blackfinger

Hiller too!



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