A point to ponder:
Let’s talk about everybody’s Favorite subject GYROSCOPIC PRECESSION. If you have a gyroscope with three degrees of freedom and you move or rotate the entire gyroscope the rotor will maintain its’ position in relation to the local horizon. If you take one of the degrees of freedom away and rotate the assembly the rotor will nutate or precess 90-degrees after the input of the changing force. The first type of gyro is used in an inertial navigation system or autopilot. The second type is used in a directional gyro. Now, let’s apply the second type of gyro to the rotor system of a helicopter. The rotating disc is the same as the spinning rotor on the gyro. The rotor disc can be commanded through control input to change its’ position relative to the local horizon. If the rotor moves with the helicopter due to the application of a local force the disc, which is maintained in position due to gyroscopic, rigidity will respond to the external force because it also exhibits precession just like the rotor on the gyro. There does not have to be relative movement between the fixed pitch link and the pitch horn to make the rotor move in this manner. As I explained to Jiff above, when the collective is at the low pitch position the pitch horn/pitch link are coincident with the flapping axis and there is no coupling. However, according to the laws of physics the rotor should nutate or precesse 90-degrees after the input of the external force. This may or may not apply to single rotor helicopters.
Propellers on fixed wing aircraft exhibit this gyroscopic turning moment but the movement is in the outer areas of the blade and the major resistant force is the crankcase bearings. On the V-22 when it is in the aircraft mode and the attitude changes the prop rotors respond by precessing as they are mounted in rubber. Any precessional movement of the prop rotor is corrected by the servo system.
Now if Nick sees it any differently let him explain it without mentioning my mental capacity or my age.
[ 16 November 2001: Message edited by: Lu Zuckerman ]
[ 16 November 2001: Message edited by: Lu Zuckerman ]