GB1353564A - Control devices of rotorcrafts - Google Patents

Abstract

1353564 Pitch control in helicopters KAWASAKI JUKOGYO KK 30 March 1972 [6 April 1971] 15222/72 Headings B7W and B7G In a control system for variable pitch blades 56 of an aircraft rotor, wherein cyclic and collective pitch control is effected by means of a swashplate 50, at least cyclic pitch is controlled by means of a link mechanism including a fulcrum 103, Fig. 2, whose position is changed according to the airspeed of the aircraft; this link mechanism is located at (a), Fig. 1. As cyclic pitch control stick 10 is moved to induce a pitching movement rods 20, 40 cause levers 104, 109 to.turn, moving rods 120, 140 which tilt the swashplate. The lever 104 tilts about the fulcrum 103, a pin engaging a slot 105, which is moved to the left by servomotor 101 as airspeed increases, while the lever 109 turns about a fixed fulcrum 110. Thus the amount of longitudinal control produced by a given stick movement is decreased as airspeed increases. At the same time the amount of lateral control, caused by tilting of the swashplate by rod 130, moved by the turning of lever 108 pivoted to an end of the lever 104, is increased; when the aircraft has zero speed the pin 103 is over the point of attachment 111 of the lever 108, Fig. 3a (not shown), so that that lever is not turned. Also, when the pin 103 is to the left the rod 120 moves less than the rod 140 so that the centre of the swashplate moves vertically and the collective pitch is changed. On the other hand, when the stick 10 is moved so as to effect lateral control by moving rod 30, the lever 108 turns about point 111 and the amount of lateral control is independent of airspeed. Collective pitch is controlled by stick 31 which moves the rods 20, 30, 40 equally; when the pin 103 is to the right this produces equal movements in the rods 120, 130, 140, but when it is displaced to the left the rods 120, 130 will move differently so that as collective pitch is changed by means of stick 31 the longitudinal and lateral cyclic pitch control is affected, to an extent increasing with the airspeed. Alternatively the link mechanism of Fig. 2 may be located at (b), Fig. 1, in which case collective pitch is not affected. The pin 103 may be returned to the right by a spring (113), Fig. 6a (not shown) in the event of servo failure, or the servo may be duplicated, Fig. 6b (not shown).