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Old 03-23-2009, 12:30 AM   #16 (permalink)
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Originally Posted by HoverHeaven View Post
Popsicle's reply isn't quite on the mark - the flybar doesn't provide any stability whatsoever, what it does is to reduce the response rate of the rotor disc to the pilots inputs.
Look at this analogy - if you place a 6-foot long pole vertically on the palm of your hand, you can balance it upright quite easily. this is because it "falls over" more slowly than you are able to respond to, or "chase", its movement.
Now try the same thing with a 6-inch pencil - it "falls over" much more quickly - too quickly for your human responses, and thus you can't keep it balanced.
This size analogy holds true for rotors directly connected to the swash - the smaller the rotor, the quicker it responds, until a point is reached where it is too quick for the human pilot to respond to or "chase".
The flybar system is actually a method of controlling the main rotor via a slower responding system which has a "chase rate" slow enough for the human pilot to anticipate - typically half a second or so, which can be changed, for example, by adding weights to the flybar to reduce the response or chase rate, (which incidentally has no effect on the stability of the system, but simply makes it easier for the pilot to follow), or by shortening the flybar or using bigger or lighter paddles to increase or speed up the chase rate
Hope this helps you to understand what the flybar does.
One of Newtons laws says an object in motion tends to want to stay in motion unless acted upon by an external force. The flybar with it's angular momentum wants to stay spinning in the same plane. Much like a bicicle wheel stabalizing the rider. The more weight (actually mass), the more force is needed to change it's plane of revolution. The amount of influence (the ratio) it has to the main gripps helps to buffer out changes in the main rotor disk from veriations in the air as well as the heli's aerodynamics and drive train. A cyclic change needs to change the angle of the flybar as well as the blade pitch.
So the heavier the paddles, the less they want to change. The more aerodynamic the paddle (wider?), the more washout inputs to paddle pitch will make that change in disk angle faster. The longer the flybar, the more leverage the paddle has to effect those pitch (paddle pitch)changes. All of this gets mixed with the direct from swash to grips by way of the mixing lever.
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