This invention relates to helicopter rotors and more particularly to rotor mounting involving a composite fiber-reinforced unitary yoke with resilient inplane restraints.

Soft inplane bearingless helicopter rotor

A helicopter rotor blade supported by a flexbeam (2) to be rotatable about an axis of rotation, in which a pitching motion thereof is allowable, is provided with a device (6) for changing the pitch and damping the lead-lag motion thereof. The device (6) comprises a bushing (13) in a through hole (2a) formed at the inboard end of the flexbeam (2), an elastomeric pivot (7) loosely fitted in the bushing, elastomeric dampers (9) of cylindrical shape mounted on the upper and lower surfaces of the flexbeam (2) and coupled with the upper and lower ends of the elastomeric pivot (7) by means of nuts (8), and torque arms (12) extending through the bushing and the elastomeric dampers (a) and having the central portion thereof connected to central shafts (7a) of the elastomeric pivots (7). Each of the pitch sleeve (12) has both ends outwardly projecting beyond the elastomeric dampers (9) and secured to a epitch sleeve (3) which encloses the flexbeam (2). Therefore, the relative position between the pitch sleeve (3) and the elastomeric pivot (7) does not change even when lead-lag motion is imparted to the rotor blade.

System for damping lead-lag motion of rotor blades of helicopter

Each rotor blade is rigidly affixed to a pair of strap members which are also rigidly connected to a rotor hub. Each strap member is defined as an elongated open box beam of rectangular cross section. Each strap member has its open web located on the side of the rectangle opposite that of its associated strap member of a pair. A pitch shaft which is located intermediate the two strap members associated with the given rotor blade, is rigidly attached to that rotor blade, and is rotatably connected with respect to the rotor hub. In alternative configurations, the strap members are configured as various alternative solid or open web designs, but all are configured as pairs having a pitch shaft therebetween.

Composite hingeless rotor hub for rotary wing aircraft

A grip-yoke assembly for attaching a helicopter blade to the mast of the helicopter rotor having a conventional primary coupling to carry the centrifugal loads and a redundant path operative should the primary coupling fail to insure continued operability of the blade. In one embodiment, the redundant load path has a bearing surface formed on the inboard end of the grip and a corresponding thrust bearing mounted on an inboard yoke fitting for engagement with the bearing surface upon failure of the coupling. In an alternative embodiment, a bearing surface is formed on an outboard grip fitting and a corresponding thrust bearing is supported on the yoke outboard of the grip fitting.

Grip-yoke assembly with a redundant centrifugal load support

A composite flexure that secures a rotor blade to a gimbaled yoke in a tiltrotor rotor system. The composite flexure includes a composite flexure member, a first end, and a second end. The first end of the composite flexure couples the composite flexure to the gimbaled yoke, and the second end of the composite flexure couples the composite flexure to the rotor blade. The composite flexure is twisted when the composite flexure is not subject to torsional loads in order to accommodate various forces imparted on the rotor system.

Composite flexure for tiltrotor rotor system

In a helicopter rotor system, a hub assembly including a blade retention member which is compressible and torsionable in installation and operation of such rotor system, the torsional stiffness of the member decreasing with increasing rotor blade speed, the compressible stress not exceeding the strength of the material out of which the member is fabricated. Its inboard end is fixedly connected to either the rotor blade or a movable hub enveloping it at its inboard end, while its outboard end is fixedly connected to the fixed hub or extension thereof in the rotor system. Means are also provided in the system for isolating bearing means supporting the blade from the blade retention member. The member itself comprises a plurality of rails spacedly disposed radially equidistant from a common centerline coincident with the feathering axis for the blade.

Howard Kastan

Papers

Rotor system including a blade retention member