GB1328540A - Method and devices for the longitudinal stability of helicopters - Google Patents

Abstract

1328540 Improving longitudinal stability SOC NATIONALE INDUSTRIELLE AEROSPATIALE 20 Nov 1970 [27 Nov 1969] 55284/70 Headings B7G and B7W A method of improving the longitudinal stability of a helicopter H is characterized in that any incipient longitudinal divergence of the helicopter is compensated by creating an opposing moment generated by an inertiaactuated stabilizer E located at the tail end of the helicopter. The stabilizer E pivotable by the inertia of a weight 12 attached indirectly thereto generates a compensating moment which when equilibrated determines a new stabilizer position having a modified lift value which generates a further moment to counteract the initial divergence. Stabilizer E is bolted on to a channel shaped support 4 forming a lever arm, and having two depending flanges 13, 14 and a weight 12. Spaced vertical flanges 17, 18 having openings 19 (20) form an intermediate member within support 4 through which the stabilizer is connected to a vertical stabilizer D by hinge pin 21 and a bell crank 25 depends from flange 18 and is adjustably mounted for setting the equilibrium position of the stabilizer E, in a slotted bracket 30 also secured to stabilizer D. Flanges 13, 14 and 17 18 are differently spaced through hinge pins 45, 46 and 43, 44. A return spring 37 limiting the moment generated, extends between stabilizer 10 and a spacer pin 39 between flanges 13, 14. Vertical flanges 17, 18 are hingedly connected to divergent links 41, 42 through pins 43, 44 the links forming part of the coupling between the stabilizers D and E. A stabilizer damper is also located between flanges 17, (18). Before operation while the helicopter is grounded support 4 is set in an equilibrium position corresponding to the degree of weight attached to the lever arm, a restraining peg (58) Fig. 3 (not shown) is then removed to allow inflight operation. In an alternative embodiment Fig. 10 (not shown) the device is mounted on a tail boom with two half stabilizers 66 projecting one from each channel section 68 located one on each side of the boom and pivotable on a common spar axis 85. The rear end of section 68 carries a weight 69 and the front carries a spring 69a extending down to a transverse arm 77 pivotable on a clevis (78) Fig. 13 (not shown) on the helicopter centre line; the section 68 is pivotable at its front between two brackets 82, 83. A damper 70 and associated linkage 72, 73 are also provided. The stabilizers could be provided with additional control surfaces and the device is especially suitable for use in a helicopter having a rotor with flexible blades, devoid of hinges.