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Old Oct 07, 2012, 05:16 AM
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Joined Jan 2012
25 Posts
full size helicopter mechanical mixing question

how is the cyclic and collective mixed on full size (passenger) helicopters
I can't find this information on the web

my best guess is
the collective is input to a plate that is raised or lowered mounted to this plate are
cranks or cams controlled by drive shafts from the cyclic that tilt the swash plate
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Last edited by rob.rice; Oct 07, 2012 at 05:25 AM.
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Old Oct 07, 2012, 09:26 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,764 Posts
'..can't find this information on the web' ?

Have you tried a Google on - How a helicopter works - loads of information. Also the Helicopter forums here have a lot of information on how it's achieved on models.
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Old Oct 07, 2012, 06:05 PM
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Joined Jan 2012
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google it the first place I go for any thing
on and off I must have spent 30 hours looking for this

rc helicopters it's simple addition subtraction after the trig that converts 2 axis to 3 servo positions
on the 4servo 90deg same thing addition subtraction with out the trig
on the 3servo 90deg swash plate models there is a servo the raises and lowers the main shaft that's NOT practical on a full size aircraft
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Last edited by rob.rice; Oct 07, 2012 at 06:34 PM.
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Old Oct 07, 2012, 07:14 PM
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Joined Oct 2004
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there's different setups on different helicopters. Generally the whole of the swashplate is lifted by the collective, and tilted by the cyclic, all mechanical mixing being earlier in the control chain. On some small helicopters the swashplate only controls the cyclic while the collective control rod runs through the center of the shaft and is mixed on the rotor mast. There's no "one size fits all" solution
[edit] this is yet another setup on a small homebuilt: http://dc441.4shared.com/doc/fMOp0kkR/preview.html
No swashplate, both cyclic and collective input is through a rod running through the main rotor shaft. The base is connected with a spherical joint to the control rod for the collective, while the cyclic operates by moving sideways the collective pushrod. This causes the rod in the rotor head to tilt as well as slide, and carries collective and cyclic inputs directly to the blades.
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Last edited by Brandano; Oct 07, 2012 at 07:29 PM.
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Old Oct 08, 2012, 12:56 AM
German Engineering.......
HugePanic's Avatar
Joined Dec 2007
453 Posts
Take a look at this:

Sorry for the german language. The three pushrods are: (from. Left to right)
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Old Oct 12, 2012, 10:49 PM
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United States, AL
Joined Apr 2007
832 Posts
Rob: You need one control input into a rotor system for each axis you want to control. So for pitch, roll, and collective you will always have three inputs to a swashplate. Where those inputs are on the swashplate varies based on all the engineering compromises made in designing the aircraft. Each input may or may not be dedicated to one axis.

On many light helicopters with simple rotor systems(like an underslung/semirigid/teetering rotor) the three control inputs are direct and independent to the swashplate. You can follow the control rod from the collective up to the rotor and see it evenly raise the swashplate. You can follow the pitch control rod and see it move the swashplate(the direction the swashplate moves for pitch/roll depends on which direction the rotor spins and the type of rotor system). And same for roll.

On heavier helicopters the controls are often all mixed together. Mixing is done mechanically with direct controls and electronically if the aircraft is fly-by-wire. The controls are mixed to make flying easier. For example, increasing collective could increase tail rotor pitch to reduce the pilot workload required to maintain yaw control.

So the answer to your question is that there is not a single answer. Were you wondering about a specific helicopter?
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