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HomeAircraftHelicopterMain Discussion › Lead lag on tail rotor
06-01-2009 06:00 AM  9 years agoPost 1
NZ_Nitro

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New Zealand

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Well does it happen? in ff will you get any lead lag as one blade will always be going back but I guess the diameter means its insignificant?

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06-01-2009 06:05 AM  9 years agoPost 2
DKNguyen

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You get all the same main rotor effects with the tail rotor, including flapping and lead/lag. Just the forces involved are smaller so the blades can handle the stress.

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06-01-2009 06:05 AM  9 years agoPost 3
NZ_Nitro

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New Zealand

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I also know it does not effect how a heli flys
or we would have trouble now but its more a theory question do full size helis have a feathering shaft on the tail?

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06-01-2009 06:09 AM  9 years agoPost 4
DKNguyen

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THere is no feathering shaft on the tail rotor- just look at at assembly manual. No dampers for the tail. It's just a solid tail hub.

I don't know if they deal with this on full-size helis (they probably do but I haven't looked into it). But for RC, adding those mechanics in is more trouble than they are worth.

EDIT: I've been reading around and it seems like full-size tail rotors are also built more simply than the main rotor because the extra effort is not worth it a lot of the time.

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06-01-2009 06:19 AM  9 years agoPost 5
NZ_Nitro

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New Zealand

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I also had a look about it
There is no feathering shaft on the tail rotor- just look at at assembly manual. No dampers for the tail. It's just a solid tail hub.
I am aware of this I have two helis of my own! its just a theory on tail rotors think of a heli doing say 60kmh forward speed while the tail rotor is controlling torque reaction from the main blades could make for some interesting thoughts

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06-01-2009 06:55 AM  9 years agoPost 6
alvinrc

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Mobile, AL, USA

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TR damping has been done on RC choppers.

My old MA Xcell heli had the TR hub isolated from the shaft by a rubber sleeve with a pin through the assembly as a hinge.

Don't know if later Xcell models or MA designs continued to use this method or was more trouble than worth, the rubber sleeve would develop wear and tear and have to be replaced on regular basis.

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06-01-2009 09:33 AM  9 years agoPost 7
ch-47c

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san jose, ca

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Yep with the Xcells and the Schluter Magic.

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06-01-2009 09:44 AM  9 years agoPost 8
DKNguyen

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Just a thought- I would imagine in those situations that any disymmetry of lift in the tail rotor could be simply overcome by the main rotor cyclic. And that the tail rotor experiences retreating blade stall after the main rotor does because the higher RPM means that more of the tail blade is moving at a higher velocity than the main blade (even though the tip speeds may be the same, the entire tail rotor blade has a similar velocity as the outermost area of the main rotor blades).

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06-01-2009 01:53 PM  9 years agoPost 9
BarracudaHockey

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Jacksonville FL

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The tail rotor is also aided by weathervaning in forward flight.

Andy
AMA 77227
http://www.jaxrc.com

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06-01-2009 02:24 PM  9 years agoPost 10
trunkmunki

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Bangor

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They do lead/lag, and there is dyssymetry of lift on a TR. On a 206, there is a delta hinge that allows the TR to flap 45deg to the axis of the blades. This accounts for dyssymetry of lift, as far as lead/lag goes, it should not be as much of a factor, as all tail blades pitch the same amount with pedal changes and therefore, after the dys. lift is taken care of by flapping, the change in lift would be the same, therefore the drag per blade should be very close (again, after flapping to equilibrium) and the lead-lag is taken care of in the same way a semi-rigid rotor system takes care of it, as on the 206 (both blades must move together, they do not lead/lag independantly).

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06-01-2009 02:38 PM  9 years agoPost 11
predatorman

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Falkland Islands

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I work on Sikorsky 61's and they have 5 blades on thier tail rotor.

These Blades can flap, the variation in pitch is taken care of by the pitch links...so the more the blade flaps the more or less the pitch...depending on what is actually taking place with the Craft at the time.

The Main Blades are attached to a fully articulated rotorhead. The variation of blade pitch is again taken care of by the pitch links

so if you took a blade and lifted it, as its leading edge/pitch horn remains in place the balde will alter its pitch or angle of attack.

I cant speak much for the other types out there, but we do have a Lynx (westland lynx)its tail rotor is the same concept in that it flaps.

Interesting about the model side of things though.

Quality takes........time!

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