To: 212 Man
There are two things in play relative to the introduction of gyroscopic precession as a means of changing disc position (tilt direction). 1) The rigidity or the disc in space which is a function of the rotating mass and the speed of rotation. 2) The force necessary to overcome the rigidity and to perturb the rotating mass. On a lightly loaded rotor system like the Robbie it can be done with mechanical input. On larger helicopters hydraulic servos are used. The servos serve two functions one is to supply the perturbing force and the second and from the pilots point of view is most important is the resisting of the feedback forces from the spinning rotor.
In either case the cyclic movement supplies the input or, perturbing force and depending on how that force was applied the resultant of that force will reach maximum response 90-degrees later in the direction of rotation. This input could be a singular input such as left or right cyclic or, fore and aft cyclic or, it can occur in combination when the cyclic is applied in a vector in relation to the X/Y axes of the helicopter. The results are still the same.
As long as the cyclic input is maintained the precession will continue until the rotor reaches the maximum deflection or, when the cyclic hits the stops. However when the pilot reaches the desired disc tilt and stops, then the precession will also stop, as the perturbing force will be removed.
The following is for Grey Area.
In diagramming the A Star dynamic system I came up with the following. If I recall correctly, you stated that when the disc tilted up in forward flight you would expect to get a roll input due to precession but this was not the case. In theory if the helicopter (any helicopter) disc were perturbed due to some external force and the rotor system and the helicopter were moved as a unit then there would be a roll. However on the A Star when the rotor (flaps back for whatever reason) the disc moves in relation to the fuselage and the swashplate is rigid to the fuselage due to the hydraulic lock of the servos. When this relative movement takes place, the movement of the pitch links in relation to the swashplate is the same as if the pilot inputted a cyclic movement in the right forward quadrant, which would nullify any tendency to roll, and would restore the rotor to nearly the position it was originally in, prior to the blow back. A minor adjustment in cyclic would fully restore the disc to the original position. (I THINK)
Regarding the Daufin (HH-65 Dolphin) I'm sorry to say no. I got out of the U S Coast guard about 25 years prior to the HH-65 coming on line.
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The Cat
[This message has been edited by Lu Zuckerman (edited 17 December 2000).]
[This message has been edited by Lu Zuckerman (edited 18 December 2000).]