ROTOR SYSTEM FOR HIGH SPEED HELICOPTERS AND A METHOD OF CONTROLLING THE PITCH OF A HELICOPTER ROTOR

摘要

1,260,384. Helicopters. FAIRCHILD HILLER CORP. 22 Jan., 1969 [25 Jan., 1968], No. 3694/69. Headings B7G and B7W. A helicopter 1 capable of high velocity forward flight has its rotor blade pitch angle varied during rotation so that it derives lift from reverse air flow over the retreating blade. The helicopter has two short blades 7 of high solidity ratio and provided with slotted flaps 10 to generate additional lift at low speeds. Additionally or alternatively other auxiliary lifting devices such as boundary layer control mechanisms or air slots could be employed. The blades are bi-symmetrical with rounded leading and trailing edges to improve reverse velocity lift generation. A counter-torque rotor 11 may be moved into an orientation in which it acts to provide forward propulsion. To control blade pitch angle and thus the angle of attack of the retrating blades a two per revolution or higher order cyclic pitch input is required. Fig. 5 shows curve A, corresponding to a one/rev pitch change and curve B a two/rev pitch change. Methods of combining a one/rev input and a two/rev input to get an input corresponding to the form of curve C are described with reference to Fig. 6 which shows a swash plate 35 to provide a conventional one/rev pitch change and a Hookes joint 49 to provide a two/rev or higher order change according to the invention. The primary cylinder 52 may be tilted relative to shaft 33 and secondary cylinder 48 by means of an input link 55 and this causes the rotation of cylinder 48 to oscillate at a slower then faster speed than cylinder 52 giving a two/rev input which is combined with that of the swash plate by means of a mixing lever. Fig. 7 (not shown) which shows a flexible plate (60) to which are attached push rods (71) attached to horns (37) the plate being in contact with rollers (65a, 65b) (63a, 63b) which may change its shape. Additional rollers may be provided in which case a higher than two order input is obtained. Figs. 8 and 9 (not shown) also show methods of input combining, Fig. 8a a crank assembly and Fig. 9 a cam arrangement. A detailed description of the embodiment employing a Hookes joint is given with reference to Figs. 10 to 14 (not shown). The relative changes for the one/rev and two/rev input may be altered.