Grav,
Almost always, delta three is induced by making the blade pitch change horn lay inboard of the blade flap hinge (for a leading horn.) This makes the blade flap about an axis that is not normal to the rotation (it flaps about a skewed axis that is 17 degrees from the tangent). This skewed flap axis makes the blade dump lift as it flaps. This make a much smoother and more stable ride for passengers.
One effect of delta three is that the control axis is rotated by that same angle, so that the phase lag (gamma) or rigging angle must be adjusted accordingly. This is what always caused Lu Z concern (rest his soul) because it is a bit hard to fathom.
Last edited by NickLappos; 11th February 2007 at 12:12.