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On Jan 20, 6:12 pm, "Steve R." wrote:
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As to helicopters, I know they morphed out of autogyros thanks to the
rotor head development of Cierva. But I don't understand how
gyroscopic precession can enter into the control of the helicopter
rotor plane when there is so much imput coming from the pilot. That
would mean his controls would be set in precession so a move to right
is really an input on the bottom of the rotor plane?


If I'm reading you correctly, you're uncertain why the control inputs are
applied to the rotor blades ahead of where you really want the rotor to
react? Maybe I'm not following you on this but with regards to gyroscopic
precession, I'll offer this.

First of all, as a spinning object, the rotor system, be it on a helicopter
or gyroplane, is a gyroscope. As such, it acts like one. One of the
properties of a gyroscope is the property of rigidity in space. That is, it
wants to maintain it's plane of rotation and resists deviating from that
plane. If a force is applied to the gyroscope that is strong enough to
force it out of it's plane of rotation, that force will be reacted to at a
point 90 degrees in the direction of rotation from the point where the force
was applied. That is the definition of gyroscopic precession.

In a rotorcraft, all cyclic blade movements that are used to change the
attitude of the rotor disk in pitch or roll, must be applied 90 degrees
ahead of where the pilot really wants the rotor to move. If the rotor is
spinning clockwise as viewed from above, or moving from the pilots left to
right as seen from the cockpit, and the pilot wants to roll the aircraft to
the left, the actual cyclic movement applied to the rotor blades should have
each blade reach it's maximum pitch straight ahead and minimum pitch back
over the tail. The rotor will react to this at a point, 90 degrees in the
direction of rotation. That will have the forward blade climb to it's
maximum point on the right side of the bird, and the rearward blade descend
to it's minimum point on the left side of the bird and she rolls left.
However the cyclic pitch movements are achieved, the result is the same.

I hope that makes sense! :-)

Steve R.