Abstract: A helicopter power train is disclosed in which the rotor tip-path plane (218) inclination relative to the helicopter air frame (200) is achieved by blade flapping motions distributed through a plurality of drive train components rather than through blade flapping motion about a single flap hinge. Rotor tip-path plane flapping is accommodated by resilient transmission mounts (24, 25, 26 and 27) to the extent of approximately 25%, by a flexible mast (208) extending upward from a transmission (11) to the extent of approximately 20%, by a hub (213) having flexure members to the extent of approximately 50% and by flexible blade structure (214, 216) having beam bending to accommodate approximately 5% of the rotor flapping motion. The hub (213) comprises a plurality of yokes (260, 262) each of which is an elongated plate having flexure members to accommodate blade flapping. The yokes (260, 262) are stacked on the mast (208) to form the hub (213).

Abstract: A mounting for a helicopter pylon having a plurality of resilient vertical support links (24-27) between the pylon (12) and the helicopter fuselage (13). The links have a composite spring rate for a given pylon weight which establishes a resilient support for the fuselage from the pylon at the thrust required to support said fuselage in normal flight and in which oscillatory vertical force transmitted to fuselage is minimal for acceptable static deflections of the pylon.Physical stops (24e, 24n, 24p) are operable to limit deflection between the pylon (12) and the fuselage (13) at predetermined rotor thrust above and below said normal thrust.Links (24-27) are mounted at the ends of a pair of rigid beams (20, 21 and 22, 23) which are secured at the centers thereof to opposite sides of transmission portion of the pylon (12).A vertical rigid mounting pin (24b) extends downward at the end of each beam.

Abstract: A helicopter landing gear assembly includes a pair of crosstubes (20, 22) having a pair of struts (28, 30) connected at the outboard ends thereof. A first of the crosstubes (22) is connected to the helicopter fuselage (16) at a pair of laterally spaced points (24, 26). The second of the crosstubes (20) is joined by a pivot connection (32) to a structural bridge (10) positioned above the second crosstube. The structural bridge (10) is connected at its outer ends to the fuselage main beams (12, 14). The structural bridge (10) connected to the second crosstube (20) permits the helicopter fuselage (16) to pivot about a fore-aft axis thereof to lower the natural roll frequency of the helicopter airframe and therefore increase the margin of stability to prevent ground resonance.

Abstract: A helicopter rotor hub assembly (10) in which a blade grip (30) extends inboard of a yoke (14) and transfers centrifugal forces to the yoke (14) through a spherical elastomeric bearing (38). Pitch change of the grip (30) and blade (32) is accommodated by the spherical elastomeric bearing (38) which also acts as the pivot point for lead-lag motion of the blade (32) and grip (30). A lead-lag damper (22) is located inboard of the elastomeric bearing (38) and is connected between one end of the grip (30) spaced away from the lead-lag pivot and the yoke (14) for damping the lead-lag motion between the grip (30) and yoke (14).

Abstract: A helicopter fuselage is coupled to a pylon to permit fore/aft pivotal movement of the fuselage relative to the pylon with resilient means connected between the pylon and fuselage to oppose and limit such pivotal movement. Structure is then provided to decouple the rotor control linkages to permit limited fore/aft rotation of the fuselage relative to the pylon upon change of location of the center of gravity without introducing control motion in the control linkages. The control linkages include control tubes extending longitudinally of the fuselage from a pilot input location. Bell cranks are connected to the control tubes and are coupled as to control the pitch of rotor blades. Structure connecting the fuselage and each bell crank alters the pivot points of the bell cranks relative to the fuselage. The positions of the bell crank pivot points depend upon rotation of the fuselage relative to the pylon.