To: Delta 3 and Delta 3
I just finished my post in response to your two posts and it disappeared. Now I have to start over again.
If I understand you correctly you state that the Robinson has a 90-degree phase angle. Hopefully I am correct in that assumption as my comments are based on that assumption.
Using the Bell system as a base line when the pilot moves the cyclic forward the swashplate tilts on the lateral axis and tips down over the longitudinal axis. With the blades disposed over the lateral axis the advancing blade will be at its’ lowest pitch and the retreating blade will be at the highest pitch. Since you believe in gyroscopic precession the reaction will occur 90-degrees later (discounting phase angle shift) and the advancing blade will be at its’ lowest point of flap over the nose. This is as a result of the rotor system having a 90-degree lead on the pitch horn.
If you believe in gyroscopic precession then you must also believe that the disc will tilt 90-degrees in the direction of rotation from where the perturbing force was input. In this case the perturbing force was over the right side of the disc and the disc tilts down over the nose as a result.
The Robinson control geometry is just like the Bell. If the cyclic is displaced forward from the rigged neutral position the swashplate will tilt on the lateral axis and tip down over the longitudinal axis. Unlike the Bell which is rigged for forward control with the blades disposed over the lateral axis the Robinson blade is rigged for forward control with the advancing blade 18-degrees ahead of the lateral axis. This is because the pitch horn leads the blade by 72-degrees as opposed to the 90-degree pitch horn on the Bell.
Following your statement about the Robinson having a 90-degree phase angle and your belief in gyroscopic precession the Robinson blade will have its’ maximum response 90-degrees after the maximum pitch change. If you believe that then the blade will dip down 18-degrees past the longitudinal axis.
Since you own an R-44 try this experiment. Place the blades over the longitudinal axis. Starting at the rigged neutral position move the cyclic laterally. The blades will move. Now, place the blades over the longitudinal axis and from the rigged neutral position move the cyclic forward and aft and the blades will move. If you performed this same test on a Bell the blades would not move.
Now, place the advancing blade so that the pitch horn is directly over the longitudinal axis. Move the cyclic stick laterally and the blades do not move. This is the position the blade is in when you rig for forward flight and in this position the advancing blade is at its’ lowest pitch and the retreating blade is at its’ highest pitch. If you believe in the laws of precession where should the blade be when it is in its’ lowest point on the tip path.
Forget about pitch flap coupling.
