To: Ark Royal Post one
The rotor system on a helicopter has the characteristics of a gyro. One, it has rigidity in space in that it will remain in the position it was placed in and will not move unless perturbed by an external force be it air flow over the disc or, input by the pilot via the swash plate.
The second characteristic is that it has a precession angle of 90 degrees +/- a wee bit. Like a gyro the rotor will move 90 degrees later in rotation from where the perturbing force was applied.
The gyroscopic phase angle will be present whether the helicopter is running up on the ground or, in the air flying in any given direction. Flapback as you call it is the result of the inflow but aside from that it has no effect on the phase angle.
It doesnt make any difference if you are dealing with a rotor system on a Bell which has a rigid teetering rotorhead or a CH-53 which has seven blades on a fully articulated rotor head. Although the blades are in effect independent of each other the disc will respond as if it were solid.
To: Ark Royal Post Two
The Bell pitch horn leads the blade by 90 degrees. Assume, that the blades can be frozen in the position of being over the lateral axis. At this point the advancing blade is at its' lowest point of pitch and the swashplate is tipped down over the longitudinal axis. 90 degrees later the disc will tip down over the nose and up over the tail.
Now we do the same thing with the Robinson. The swashplate is tipped down over the longitudinal axis. The blades are disposed over the lateral axis. Now, check the position of the rotating portion of the swashplate in relation to the stationary portion. In order to reach the maximum down pitch the blade must rotate an additional 18 degrees (approximately) which will cause it to tip down fully at some point to the left of the longitudinal axis. It may not be 18 degrees to the left but it will be far enough left that corrective input must be made to the cyclic.
On an articulated rotor head the pitch horn leads the blade by 45 degrees and the swashplate tips 45 degrees ahead of the point where the rotor would be tipped. This gives 90 degrees.
To: Imlanphere
According to the FAA Rotorcraft flying hand book Page 3-6 (Trasnsverse flow effect).
...the result of transverse flow effect is a tendency for the helicopter to roll to the right as it accelerates through approximately 20 knots. If that is true you would move your cyclic stick to the left. However, in your post you said that you would move the stick to the right to counter transverse flow effect. If the hand book is correct then what you are doing is compensating for the 18 degree off set and not transverse flow effect. Is this what they told you in Robinson flight school?
[This message has been edited by Lu Zuckerman (edited 24 November 2000).]
[This message has been edited by Lu Zuckerman (edited 24 November 2000).]
[This message has been edited by Lu Zuckerman (edited 24 November 2000).]