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So I've seen a couple threads here and elsewhere regarding futuristic helicopters, etc- and I'm probably just a couple years late on this discussion- but I haven't seen any discussions on the VTOL aircraft from Avatar and how plausible it would be to make such an aircraft. Please forgive me if my newbie understanding of physics makes this question ridiculous, but MAN those things sure look like fun to fly :P

 

Seems like the rings around the props would get in the way of relative wind and thereby decrease lift capabilities, but if the blades are more like V-22 Osprey blades and the rotors have faster tilt maneuverability, then it seems like it shouldn't be a problem. I'm guessing the biggest problem lies in power/weight ratio. Any thoughts?

 

*Note* In doing a picture search, I found that they do apparently make a working RC model...that seems somewhat promising.

post-24975-0-05742900-1317755153_thumb.jpg

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I have never seen a working real helicopter with rings around the rotors. :lol: They do this with rc toys that are meant to be flown indoors. The reasons for it are safety, durability, and to minimize collateral damage when you hit something... Say your mothers/wifes favorite house plant.

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I would think it could be done, but I am no engineer. I would say one thing, since there are no guide vanes between the stacked rotors, they would have to be counter rotating. They maybe could even leave the rings in there. After actually opening the picture this time I see it apears they are used like a fan duct on this model.

 

With the fly by wire and stabilization systems they have these days I think it could be done, but the qustion would be why? You couldn't fly it with the rotors tilted full forward like the Osprey (It has no wings for lift). I guess you could say it has small wings, but they look more like weapons pylons than wings to me.

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You couldn't fly it with the rotors tilted full forward like the Osprey (It has no wings for lift). I guess you could say it has small wings, but they look more like weapons pylons than wings to me.

 

I was wondering about that- if the lift generated from the rotors alone could "pull" it through the air like a FW or if it would need the wings for added lift.

 

Also, are the dual opposing rotors in the scorpion a realistic design? Would there be any benefit to that, i.e. would it actually create more thrust? I know the Russian blackshark and Bell X2 have a similar system with the purpose of eliminating the need for a tail rotor, but is it in use in anything like the avatar scorpion today?

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I thought this might apply to a hovering toy with a shroud around its rotor and would be more productive than criticizing liberals on the Yahoo comment boards.

 

I don’t think a shroud around the rotor would permit anything other than a hover.

 

A tidbit of trivia:

 

Momentum theory is the simplest method that describes a lifting rotor. Momentum theory assumes a streamtube or slipstream boundary isolates the flow through the rotor. This method of analysis posits that changing the momentum of air passing though the rotor creates lift. Air enters the streamtube, is accelerated though the rotor disk, and exhausted through the bottom. Momentum theory also assumes the flow is incompressible, constant, and one-dimensional. Although momentum theory is simple, it forms the bases for more elaborate mathematical treatments of rotor dynamics; moreover, it is applicable to coaxial and tandem rotor designs and ducted fans. Lastly, in the same vein, actuator disk theory of a rotor also assumes air pressure difference on both sides of the rotor disk.

 

Leishman, J. G. (2006). Principles of helicopter aerodynamics.(2 ed.). New York, NY: Cambridge University Press.

 

Seddon, J., & Newman, S. (2011). Basic helicopter aerodynamics.(3ed.). Chichester. West Sussex: Wiley

Edited by Tom22
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Alright, so we've established the rotor shrouds need to go to increase performance. With that out of the way, is this a feasible platform? I guess what I'm really asking is, is there technology out there that would allow for thin enough drive shafts to drive the dual opposing rotors fast enough to produce the thrust needed to get this baby and its payload off the ground? By all accounts, it seems like an airworthy design to me. So what am I missing? Why haven't we built it yet?! :blink:

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Alright, so we've established the rotor shrouds need to go to increase performance. With that out of the way, is this a feasible platform? I guess what I'm really asking is, is there technology out there that would allow for thin enough drive shafts to drive the dual opposing rotors fast enough to produce the thrust needed to get this baby and its payload off the ground? By all accounts, it seems like an airworthy design to me. So what am I missing? Why haven't we built it yet?! :blink:

 

Cost and need. What benefits do you see in a design like this compared to what we have? :huh:

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Also I noticed in the Sikorsky X-2 thread that they're going to be working toward making the S-97™ RAIDER™ a reality(pic below).

 

I would think an airframe like the Scorpion would be able to achieve the same 230knot cruising speeds if not better(Osprey cs is 240K+), and would save the added weight of the tail rotor. Why not try this design instead?

post-24975-0-54902600-1317913010_thumb.jpg

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Cost and need. What benefits do you see in a design like this compared to what we have? :huh:

 

Same or better maneuverability as a helicopter, high cruising speed(all hypothetical for now of course). Just looks fun as hell to fly too :P

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So after looking at a couple threads here- one on the S97 Raider, and one on the vertical lift added by canting the blackhawk tailrotor 20 degrees- I was contemplating the Scorpion design and gary-mike's question of cost, need, and benefits, and came to the conclusion that it does need something to set it apart in terms of added benefit, and came up with the design below. Forgive the horribly crude artwork :unsure:

 

So the idea is to add a swiveling "duct fan" or fenestron to the tail with single or dual rotating shaft inputs. The picture somewhat downplays the size of the blades and the tail fan, which could be made wider for longer blades and added thrust/lift. Of course depending on the length of the tail and the size of the blades, a third turbine engine could be added(probably just a smaller one). The tail fan could be angled to deliver downward thrust for added lift in a hover, then angled forward to deliver thrust for forward flight and increase cruising speed. It could also be adjusted to give forward thrust for added maneuverability in hovers and/or "air braking" to aid in slowing down from high cruising speeds.

 

In terms of having the added control inputs to deal with, I think a fly-by-wire system with either a thumb-operated "mini-joystick" on the cycle or even a mouse-style scroll wheel would make for quick, easy adjustment :P

 

Any thoughts?

post-24975-0-31762400-1317921432_thumb.jpg

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