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Old 03-23-2009, 03:05 AM   #18 (permalink)
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Originally Posted by david.lunn View Post
....I'm curios why the manufactures dont just do away with flybars than?....
I am really surprised that Finless hasn't weighed in on this... What you are reading is only half the story. While rotational momentum is important to how a heli flies and its stability. Flybar mass does slow the blades response to control inputs etc. But why are their paddles and not just weights??? Well you probably figured out that because they catch air and that moving air creates force which acts upon your blade grips. All that you have read so far is largely TRUE, for a heli in a hover. The better question is why when Igor Sikorski (who really invented the helicopter) had an amazing problem... his heli's hovered just fine but when they moved forward with any speed... they flipped over....

Why??..... Relative Wind! When a heli moves in any direction the wind and thus air mass encountered by the blade advancing into the wind (relative wind is created by its motion through still air) has more lift than the blade retreating from the wind.

I could get much more detailed but your flybar has paddles so that it can achieve directional flight at any appreciable speed. When the flybar encounters relative wind it acts to reduce the pitch of the advancing blade and decrease the pitch of the retreating blade. Flybarless systems monitor motion of the vertical axis and absent control inputs take actions to keep that axis in a constant orientation... think heading lock gyro for your rotor head but in two axis's instead of one.

Thx Igor.

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