To: Fr. O’Blivien
You stated:
“There is no fore and aft (cyclic) movement in either disk. (There can’t be, they’d strike each other) Aircraft pitch is controlled by differential collective between the disks”.
You further stated,
“Actually there is a slight fore and aft input by a system called LCT (Longitudinal cyclic trim) that tilts the gearboxes fore and aft to reduce excessive deck angle at speed, but it is not part of the primary flight controls. Conventional flight controls produce these rather unusual inputs via a very complex mechanical mixing unit in the broom cupboard behind the P1”.
Actually, there is a forward cyclic component but it is not introduced by the forward tilting of the gearboxes. An electromechanical actuator that is attached to an arm extension of the swash plates introduces forward cyclic. It does not actuate until the helicopter reaches a forward speed in excess of 60 Knots (approx.). Since the blades intermesh, they can’t contact each other when cyclic is input is made by the automatic system. The pilot does not have direct control of this system and therefore the pilot can’t perform a cyclic flare while flying forward. He can introduce a cyclic flare while flying sideways and because of this, autorotatations must be entered into while flying sideways.
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The Cat
[This message has been edited by Lu Zuckerman (edited 30 April 2001).]