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....(see link for more)
Inventor: Wesley L. Cresap Assignees: Bell Helicopter Textron, Inc.
1. A helicopter power train including a transmission for driving a multi-blade rotor for accommodating rotor tip-path plane flapping deflection comprising in combination:
(a) a resilient mounting including a plurality of independently operating mounts with travel limits for coupling the transmission to the fuselage of the helicopter, said mounting to accommodate from about 15% to 35% of said deflection,
(b) a flexible mast extending from said transmission to said rotor to accommodate from about 10% to 30% of said deflection,
(c) a yoke secured to said mast for connecting said blades to said mast, said yoke having a thin flexure section immediately outboard of said mast to accommodate from about 40% to 60% of said deflection, and
(d) each of said blades including means for providing beam bending to accommodate from 0% to about 10% of said deflection.
2. A helicopter power train as recited in claim 1 wherein said resilient mounting includes a load-bearing elastomeric member.
3. A helicopter power train as recited in claim 1 wherein said flexible mast comprises a tubular member extending from said transmission to support said yoke and drive said blades.
4. A helicopter power train including a transmission for driving a multi-blade rotor for accommodating rotor tip-path plane flapping deflection comprising in combination:
(a) a resilient mounting including a plurality of independently operating mounts with travel limits for coupling the transmission to the fuselage of the helicopter, said mounting to accommodate approximately 25% of said flapping deflection;
(b) a flexible mast extending from said transmission to said rotor to accommodate approximately 20% of said flapping deflection;
(c) a yoke secured to said mast for connecting said blades to said mast, said yoke having a thin flexure section immediately outboard of said mast to accommodate approximately 50% of said flapping deflection; and
(d) each of said blades including means for providing beam bending to accommodate approximately 5% of said flapping deflection.
5. A helicopter drive train including a transmission for driving a multi-blade rotor where rotor flapping tilts the blade tip-path plane to an angular deflection with regard to the helicopter fuselage, the combination comprising:
(a) a resilient mounting including a plurality of independently operating mounts with travel limits for coupling the transmission to the helicopter fuselage, said mounting statically accommodating a pre-established percentage range of the total said angular deflection,
(b) a mast extending from said transmission and having beamwise flexibility for statically accommodating a pre-established percentage range of the total said angular deflection;
(c) yoke structure secured to said mast for supporting said rotor blades and including a flexure segment immediately outboard of said mast for dynamically accommodating a part of said rotor flapping to accommodate a pre-established percentage range of the total said angular deflection, and
(d) each of said blades including means for dynamically accommodating a part of said rotor flapping to accommodate a pre-established percentage range of the total said angular deflection.