Passive Torque Control
Passive Torque Control
(OP)
HEllo all...my apologies for activating a new thread, but I didnt see my issue discussed...
Im curious how the community views the idea of affecting torque control from captured rotorwash?
Notwithstanding the complications and variables associated with foward flight and considering a stationary hover only, is it theoretically possible to introduce pitchable surfaces into the rotorwash in order to generate adequate sideways counter directional thrust and retian yaw flight control?
Further, given the linear increase of rotor disc down flow field velocity as one moves out radially from the hub, would it be within the scope of imagination to construct a rotor that promotes and greater force near the hub by adding significant depth and twist to said rotor blade.
Therefore, by creating more downflow in closer to the fuselage, the passive torque control system could be more compact and efficient with respect to total drag.
This is my first post!
Im curious how the community views the idea of affecting torque control from captured rotorwash?
Notwithstanding the complications and variables associated with foward flight and considering a stationary hover only, is it theoretically possible to introduce pitchable surfaces into the rotorwash in order to generate adequate sideways counter directional thrust and retian yaw flight control?
Further, given the linear increase of rotor disc down flow field velocity as one moves out radially from the hub, would it be within the scope of imagination to construct a rotor that promotes and greater force near the hub by adding significant depth and twist to said rotor blade.
Therefore, by creating more downflow in closer to the fuselage, the passive torque control system could be more compact and efficient with respect to total drag.
This is my first post!





RE: Passive Torque Control
RE: Passive Torque Control
Thanks so much for your advise, but you speak of aviation problems maybe as a foregone conclusion and yet there is so much to come. With respect to tip jets, you are trading one complex active power system for another and its downfall in my opinion, but I mean that with respect.
RE: Passive Torque Control
Thanks for your comments but I think you may have misunderstood what I though I had said. Badly written on my part possibly. I do not consider aviation problems as a foregone conclusion. The first line on my post maybe should have read " Its good to know that I am not the only person thinking of alternate ways to overcome aviation problems."
You may be correct about trading one complex power system for another, but it does dispose of the requirement for a tail rotor to overcome torque. It is then quite easy to use an alternate and simple system (of which there are many)for yaw control.
Two of the most successful tip jet helicopters (Djinn and Fairey ultralight) suffered from the same restrictions, fuel consumption and blade life. Other than that they were reported by test pilots to be the easiest and most enjoyable helicopters to fly. Both of these helicopters were designed and built in the early 50s and I think the problems they suffered can easily be overcome with modern technology.
Just as a side note I was onboard a military helicopter that lost tailrotor control, a very scary experience. Two weeks later I saw a friend die in the wreckage of another helicopter which suffered an identical failure. These incidents were both caused by mechanical failure and after much research over the past 20 years I am convinced that avoiding torque is better than trying to overcome it.
I think that in essence we both have a similar aim, to "get rid of the complex and fragile tail rotor". I wish you all the best and hope we can bounce ideas of each other.
Karl.
Fixed wing is just a passing phase.
RE: Passive Torque Control
RE: Passive Torque Control
Once, I also played with the idea of using a wing-like tail-boom in the down wash to counter torque. My conclusion at the time was that the surface area needed to be too high to be practical and that the rotation in the down wash even increased the already high "induced drag" (pointing downward) thus requiring an even higher lift-force and consequently a higher torque.
To give you an idea:
When the power P required for hovering the helicopter is approximately (without counting the extra losses in rotational momentum etc… ):
(1) P = Sqrt( W^3 / (0.5 * ? * Pi * d^2))
W = Helicopter weight
? = air density
d = rotor disk diameter
When the rotation speed of the blades is Rot, then the torque moment M is:
(2) M = P / Rot = Sqrt( W^3 / (0.5 * ? * Pi * d^2)) / Rot
This moment has to be countered by a moment produced by the lift on the tail-boom-wing. Considering this wing of length d/2 (only towards the back of the helicopter and in the down wash). Assuming for simplicity, a constant chord lenght and a constant cl-distribution, then:
(3) M = 0.5 * ? * v^2 * cl * c * 0.5 * (d/2)^2
v = down wash air-speed close to the rotordisk:
(4) v = Sqrt(W / (0.25 * ? * Pi * d^2 ))
c = chord lenght
cl = lift coeficient
Substitution of (1) in (2), (4) in (3) and finally (2) = (3) you find:
(5) c = Sqrt(32 * Pi * W / ?) / (cl * d * Rot)
Now some numbers:
Say: W = 14000 N, d = 10 m , Rot = 45 rad / s (numbers representing a typical helicopter like the jet ranger for example), ? =1,225 kg/m^3, (cl = 1 for simplicity, which is even on the high side)
Then c = 2,4 m
Conclusion: with a wing of 5m in the down wash you need a chord of almost 2,5 m! (A surface of about 12 m^2) Of course by increasing wing-chord towards the back (blade tips) and reducing towards the front (blade root) you could reduce that surface a bit.
Regards,
OneMoreChance
RE: Passive Torque Control
should be v = Sqrt(W / (0.5 * ? * Pi * d^2)), so (5) becomes:
c = 2 * Sqrt(32 * Pi * W / ?) / (cl * d * Rot)
in the example the chord c would become almost (5m) the same as the span d/2 (5m) of the wing!
RE: Passive Torque Control
Our goal is to evolve away from any tail configuration whatsoever, passive or active, while at ther same time not trading it for coaxiality, tandem, intermesh, or "tip jets" and so one is left with creating the desired moment forces by applying the ENTIRE fuselage body as the "wing"...there is only one fuselage shape that will accomplish this...are you following
RE: Passive Torque Control
Do you mean to shape the fuselage as a vertical wing over the whole diameter of the rotor, from back to front?
Anyway, there are more options also. I am not kidding; one option could be for example to drive the rotors not by rotating them, but by flapping them. When moving the rotor blades up and down, they will create a lift and be pulled into rotation. In that way they work like a birds wing flapping up and down creating lift and thrust. The torque action – reaction is now directly between the air and the blades leaving the fuselage with only a very small torque due to the friction in the bearings. By moving some blades up while others move down, the overall up-down motion of the fuselage can be avoided. This is not a joke. Some people are already studying this possibility for future helicopters, (for example at the Delft University of Technology in the Netherlands).
RE: Passive Torque Control
http://www.unicopter.com/0002.html
http://www.unicopter.com/1492.html
http://www.unicopter.com/1427.html
http://www.unicopter.com/1481.html
And one not so wild idea.
http://www.unicopter.com/1121.html
Dave J.