Contra-rotating Main Rotors

[LowNSlow]

I'm working in Kazakhstan and saw a Kamov heli buzzing around yesterday. Funny looking thing with the twin rotors on the same axis. . .. .I understand how a conventional and a NOTAR heli works but how do they turn a machine with no tail rotor. It did have large vertical fins and thus I assume rudders which would work in forward flight but what happens when you want to turn in the hover?. .. .As an aside, I've always it funny that the US machine with a different (read strange) rotor system also begins with a K (Kamen)

[Grainger]

Differential torque between the two main rotors does the turning in place of tail rotor.

[RW-1]

Kamen aircraft have intermeshing rotor systems.. .. .Not specifically like a H-46, but where you have two masts, angled out laterally somewhat, and independant rotors on each.. .. .Torque management is the same though I believe for turning the craft.. .. .Kamen also makes the H-2 Seasprite for USN, and while only having one rotor, it has a uniqueness in having an actual controlling flap on the rotor blade itself. Anyone know of others that have that feature?. . . . <small>[ 28 March 2002, 15:31: Message edited by: RW-1 ]</small>

[H-43]

I don't exactly know how the Kamov yaw system works but would assume that because the rotor systems are in line with each other the only way would be differential pitch which in turn causes differential torque and causes a yawing force on the fuselage.. .. .The Kaman helicopter use differential pitch as well as tipping one disk forward and the other aft during yawing turns. It helps pedal authority a little.. .. .It would be interesting to fly the Kamov rotor system or talk to someone that has. I wonder if it has the same "dwell zone" in the middle of the collective where there is very little if any pedal authority.

[Thomas coupling]

Low'n slow: with a signing off slogan like that, some might regard your nick name as appropriate, and would most probably deem your residence appropriate too...however, i could not possibly comment.. <img border="0" title="" alt="[Embarrassed]" src="redface.gif" />

[Dave Jackson]

LowNslow,. .. .Some or all of the Kamov coaxials mechanically switch the pedals when the craft enters autorotation.. ._____________. .. .RW-1,. .. ."In 1930, Corradino d'Ascanio of Italy built a relatively successful coaxial helicopter, which flew under good control. His relatively large machine had two, two-bladed, counterrotating rotors. Following the work of de la Cierva, the blades had hinges that allowed for flapping and a feathering capability to change blade pitch. Control was achieved by using auxiliary wings or servo-tabs on the trailing edges of the blades, a concept that was later adopted by others, including Bleeker and Kaman in the United States." ~ from an <a href="http://www.flight100.org/history/helicopter.html" target="_blank">article</a> by Professor Gordon Leishman.. .. .Professor Celi, who is also at the University of Maryland, is working on advanced blade control, which I believe uses tabs.. .____________. .. .H-43,. .. .The are a couple of Kamovs in Western Canada, which are used for logging. One was/is based in Victoria. That's not too far from you.. . . . <small>[ 28 March 2002, 19:48: Message edited by: Dave Jackson ]</small>

[C4]

From what I heard, the kamov has a great big brake unit which slows one of the main rotor systems creating the differential for turning in the hover, could be?????. .. .edited for spelling gremlins. . . . <small>[ 29 March 2002, 03:33: Message edited by: C4 ]</small>

[LowNSlow]

Thanks for the info people. I would imagine the system has more disadvantages than advantages or every heli would have two main rotors <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" />

[Dave Jackson]

LowNSlow,. .. .Not necessarily so. <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . .. .The latest and greatest has two rotors. [V-22] <img border="0" title="" alt="[Eek!]" src="eek.gif" /> . .. .___________. .. .Edited to add the following propaganda. <a href="http://www.unicopter.com/B280.html" target="_blank"> Good copter -?- Bad copter</a>. . . . <small>[ 30 March 2002, 00:03: Message edited by: Dave Jackson ]</small>

[C4]

Might be the latest, but definitely not the greatest!! (Yet). .. .Sadly, US Marine corp knows all about that..

[paulo]

[questions from a f/w flyer...]

Why didn't Kamov's rotors take off? (For want of a better pun).

Or didn't they really make it easier? With no torque effect, it just looks like one less complication in the horrendous stability madness that rotary flying appears to be :)

Oh, and whilst we're here, if the budget runaround Hiller had auto something-or-other, where it could hovver when flown by a couple of sandbags (see latest 'Pilot' mag), then why hasn't that kind of thing become common place, at least for basic trainers?

[Dave Jackson]

paulo,

What nice questions.

The real reason why the single rotor helicopter became predominant is classified. This is it; but don't tell anyone else. The Russians (with their coaxials) and the Germans (with their intermeshing) fiscally lost WWII, where as the Americans (with their single rotor) won.

The intermeshing synchropter was used by the US to train pilots for a short while. They then stopped because the intermeshing was too easy to fly and the pilots were not getting the training required to fly single rotor helicopters.

Lu,

This might start a bigger controversy than gyroscopic precession. :)

[ShyTorque]

Dave,

Gyroscopic precession doesn't happen on this type of helicopter;)

Uh-oh, now we've gone and done it again!:rolleyes:

[Robbo Jock]

How do you get an intermeshing rotor design to yaw ? Is it by hooking up the yaw pedals to introduce (very slight?) differential cyclic changes to the two rotors ?

[Hone22]

Yep you got it Robbo,

If both rotor systems are producing torque - 1 cancelling/opposing the other you will be able to effect yaw control by pedals either

1. Slight tilt of one disc fwd while the other back .

2. Slight pitch inc in one disc + dec in the other ....... therefore different/uneven torque, a/c will turn with the larger torque reaction.

or a mix of both.

mmmmmmm 1/2 bottle of very nice chardonnay followed by a "stonking" coffee. Luverly mix! I recommend it!!:D

Now I just need somewhere warm and soft to curl up.

G'night