Ka-50´s flaws (I think)

[sobek]

It has a swashplate, it's just on the bottom of the main gearbox instead of above it like every other helicopter in the world. Wires can't feather rotor blades, you still need hydraulic boosters for that, which means you have to have a swashplate, no way to get around that unless you build the control surfaces into the trailing edges of the rotor blades.

 

The rotor head is hingeless in the sense that there are no flap or drag hinges, but the blades still have feathering hinges. This design is already in use in many helicopters, such as the Lynx and the Bell 412, etc. The main difference with the X2 is that the blades themselves are stiffer to keep them from flexing as much as a typical rotor blade, thus allowing the two disks to be mounted very close together.

 

I stand corrected ;)

 

With hingeless i meant of course with a feathering hinge.

 

Does this concept include elastomeric bearing usage to incorporate flapping or is the blade root completely stiff?

Edited December 1, 2009 by sobek

[AlphaOneSix]

I stand corrected ;)

 

With hingeless i meant of course with a feathering hinge.

 

Does this concept include elastomeric bearing usage to incorporate flapping or is the blade root completely stiff?

 

There are elastomeric bearings for the feathing hinge, everything else is completely stiff, although there is going to be a small amount of flexing during operation.

[sobek]

There are elastomeric bearings for the feathing hinge, everything else is completely stiff, although there is going to be a small amount of flexing during operation.

 

Interesting. How can this work out, i mean, this does not qualify as a fully articulated rotor system then, does it? Is the coaxial design sufficient in canceling out disymmetry of lift?

[AlphaOneSix]

Interesting. How can this work out, i mean, this does not qualify as a fully articulated rotor system then, does it?

 

Correct, it's a hingeless rotor head.

 

Is the coaxial design sufficient in canceling out disymmetry of lift?

 

Yes.

[Hunt3r.j2]

Correct, it's a hingeless rotor head.

 

 

 

Yes.

Can a coaxial helicopter be designed with a rigid rotor system?

[AlphaOneSix]

Sure they can.

[Hunt3r.j2]

Sure they can.

Then wouldn't that fix the "rotors colliding" problem for all but the worst case scenarios?

 

That, and I don't understand why there's an inherent fear of coaxial design. R/C helicopters do it and they seem to fly perfectly. Why not use it in a real one?

 

A modded Sikorsky X2 attack helo with said avionics, more power, tougher design, lots of armor all around, fuel, yadda yadda, make it combat tough, would be quite desirable if it could also keep it's 250 kt cruise speed. Now... if someone tested this out in X-Plane...

[EtherealN]

Well, there are some very serious difficulties in testing things with miniatures - things change very rapidly when size increases, which is why most insects don't have issues falling 50 times their own height, carrying 50 times their weight or for that matter why you only see R/C helicopters maintain a hover while inverted. So while I also do not agree with the general distrust of co-axial designs I would also say that it's dangerous to use R/C experience as an indicator for what an 8 tonne helicopter can do.

[Tango]

It all comes down to material strength.

 

A 2ft plank of wood is quite hardy, doesn't bend much under its own weight etc.. but you make that plank 20 ft, and you could easily break it.

 

Just look at what is required to make a full-size helicopter aerobatic. The Lynx is a great example - the standard design can't loop, but when it is has toughened blades, it can. If you tried to loop in the standard model, the flex of the blades would be such that whilst inverted it would cut its own tail off.

 

That fact the Shark is so manouverable without suffering a blade collision is quite something.

 

I think the co-axial rotor design is superior to the usual single-rotor/tail-rotor combo because of all the inherent problems with tail-rotor based helis.

 

The only real downside to co-axial (the ability to whack the blades together) out-weighs all the problems of the single rotor design IMHO. I don't think there is anything that suggests a co-axial design is less reliable, either.

 

Best regards,

Tango.

Edited December 2, 2009 by Tango

[Hunt3r.j2]

Well, there are some very serious difficulties in testing things with miniatures - things change very rapidly when size increases, which is why most insects don't have issues falling 50 times their own height, carrying 50 times their weight or for that matter why you only see R/C helicopters maintain a hover while inverted. So while I also do not agree with the general distrust of co-axial designs I would also say that it's dangerous to use R/C experience as an indicator for what an 8 tonne helicopter can do.

Well, that and the Russians have done it, and they didn't have fancy schmancy FBW to control the Ka-50, so we know that it's quite stable and good.

[sobek]

Yes.

 

Why does Kamov bother to build their choppers with fully articulated rotors then (to this very day, i know of course that that design was probably not researched enough at that time, but, i mean hingeless designs are becoming pretty common at present)?:huh:

[mvsgas]

It could be commonalty with other systems, it could be cost of development, requirement from the costumer....

[sobek]

It could be commonalty with other systems, it could be cost of development, requirement from the costumer....

 

But this could really help to minimize the 2 biggest flaws of the coaxial design, risk of blade intersection and rotor boom drag.

[Hunt3r.j2]

But this could really help to minimize the 2 biggest flaws of the coaxial design, risk of blade intersection and rotor boom drag.

Yes, but once again you deal with the system that is Army procurement.