Patent GB-732149-A (GB)
Title: Improvements in or relating to flight-controls for aircraft provided with rotary wing structures
IPC: B64C27/625
Filed: 1953-01-06
Abstract: 732,149. Helicopters. SOC. NATIONALE DE CONSTRUCTIONS AERONAUTIQUES DU SUD-EST. Jan. 6 1953 [Jan. 14, 1952; Nov. 5, 1952], No. 430/53. Class 4. [Also in Group XXXII] A flight control for rotorcraft having each rotor provided with at least two variable pitch blades pivoted on a hub carried by a driving shaft, the cyclic pitch control comprising a swash plate or ring associated with a gyroscopic flywheel driven by said shaft and universally mounted thereon, is characterized by comprising means for causing the axis of said flywheel to follow up inclinations of the axis of the swash plate or ring after a predetermined time delay, and means for modifying the incidence of the variable pitch blades in response to inclination of the flywheel axis with respect to the driving shaft. Means may be provided to modify the pitch of the blades momentarily during the response delay of the flywheel. In the embodiment of Figs. 4 and 5, the swash ring 13 is pivoted at 35 to the yoke of a fork 34, the tail of which is rotatably mounted in a member 36, thus allowing the swash ring to tilt universally. Member 36 is mounted by levers 37, 40 pivoted to a collar' 38 integral with the housing 39, and the linkages are so dimensioned that rocking of lever 40 by the collective pitch control rod 41 raises or lowers pivots 35 parallel to the driving shaft 14. Two levers 11, 12 are connected at their upper ends to the swash ring and at their lower ends to rods 9, 10 connected to a universally mounted control lever (Fig. 2, not shown) depending from the cabin roof, so that longitudinal movement of the control lever operates rods 9 and 10 together, to tilt the swash ring about a lateral axis, and lateral movement of the control lever tilts the swash ring about a longitudinal axis. Two double acting spring boxes centre lever K to a neutral position which may be trimmed. Mounted by a ball race 15 on swash ring 13 is a star coupling member 16, having three bevelled shafts 42 supporting three levers 43, 44, 45 in the reamed ends 46, 47, 48 of which are rods 49, 50, 51, extending at right angles to the axes of shafts 42, and meeting on the drive shaft axis, and having faired masses 52 at the outer ends, constituting the gyroscopic flywheel. The three arms bear slidable rotatable collars pivotally interconnected by members 53, 54, 55. The blade roots 64 of the blades 65 are mounted on flapping hinges 66 and drag hinges 67, being damped about the latter by levers 68 and dampers 69. The incidence of each blade is controlled by a rod 60 connecting a lever 70 fast to the blade roots 64, and a yoke 59 at the inner end of the flywheel arm preceding the blade. Flapping of the flywheel arms about shafts 42 is hydraulically damped (see Group XXXII). The control sequence is that on operation of the collective pitch lever, pivots 35 are raised to raise the flywheel parallel to itself and alter the blade incidences collectively in known manner. On tilting the swash ring, the flywheel arms tend to maintain their plane of rotation in space, i.e. to flap relative to the tilted swash ring. This flapping movement is gradually damped by the hydraulic dampers to bring the plane of the flywheel into the plane of the swash ring, and thus change the incidence of the blades cyclically through connecting rods 60. The swash plate is driven by a compass 61 from the rotor blade hub. Fingers 97 on the blade roots are adapted to contact extensions 96 of a member 62 fast to the blade hub, to prevent the flywheel arms dropping when the rotor is not rotating. In a modification (Fig. 9), a lever 106 is secured to each lever 43 about the shaft 101, and a yoke 102 formed on the star coupling member bears a pivot 114 pivoting a bell crank lever 109, 111. Arm 109 and lever 106 are connected by a rod 107. When the swash ring tilts, star coupling member 100 tilts also, lever 106 remaining in position due to gyroscopic inertia, while pivot 114 rises or lowers with the swash ring, raising and lowering bell crank 109, 111, bodily, to move the incidence changing rod 113, corresponding to rod 60 of Figs. 4 and 5. When the flywheel tilts after the response delay, lever 106 also tilts, to rock bell crank lever 109 about pivot 114, to move incidence rod 113 to its final position. Rod 107 can be pivoted to lever 106 at 115, 116 or 117 to vary the amount of the change of incidence obtained without delay.