# What is the effect of changing the angle of a helicopter flybar?

A helicopter flybar is a kind of gyroscopic stabilizer which acts in feedback to the pitch of the blades. The effect, in words, is that as the helicopter starts to pitch or roll in a particular direction more lift is applied on that side, keeping the helicopter level. These devices are commonly found on the inexpensive RC helicopters which are on sale at all major department stores. An example of the flybar from one of these RC helicopters is shown below.

Although it isn't obvious from the picture, there is an angle between the flybar and the rotors. On my RC helicpoter at home the angle is roughly $35^\circ$. I believe that this angle has the effect of introducing extra phase in the feedback loop.

My questions are:

• What is the effect of changing the angle between the flybar and the rotor?
• How can I mathematically describe the effect of this angle?
• What would happen if the angle was changed to $90^\circ$? What about $0^\circ$?