Blade attachment for a bearingless rotor of a helicopter

Patent metadata

Field	Value
Publication number	US-9718542-B2
Application number	US-201313803009-A
Country	US
Kind code	B2
Filing date	Mar 14, 2013
Priority date	Apr 18, 2012
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

A blade attachment ( 1, 20 ) for a bearingless main rotor of a helicopter with an airfoil blade ( 2 ), a flexbeam ( 3, 21 ) including a flexbeam body ( 16, 17 ) and a flexbeam head ( 13 ) at an end of the flexbeam body ( 16, 17 ). A control cuff ( 4, 22 ) encloses and extends along at least a predominant portion of the flexbeam ( 3, 21 ). A separable junction arrangement between the flexbeam head ( 13 ), the control cuff ( 4, 22 ) and the root end of the airfoil blade ( 2 ) is mechanical with removable fasteners. The removable fasteners comprise a main bolt ( 7 ) and at least one supporting bolt ( 8 ).

First claim

What is claimed is:

1. A blade attachment for a bearingless rotor of a helicopter, comprising:
an airfoil blade having a tip end and a root end forming opposite ends thereof and having a pitch axis from the tip end to the root end;
a flexbeam including a flexbeam body and a fork-shaped flexbeam head at an end of the flexbeam body, the flexbeam body being flexible;
a control cuff enclosing and extending along at least a predominant portion of the flexbeam;
a separable junction arrangement between the flexbeam head, the control cuff and the root end of the airfoil blade, wherein the junction arrangement is mechanical between the flexbeam head, the control cuff and the root end of the airfoil blade with removable fasteners respectively removably connecting the root end of the airfoil blade and the control cuff with the flexbeam head, the removable fasteners comprising a main bolt and a supporting bolt both arranged lying perpendicular to the lead-lag pivoting plane of the airfoil blade and being asymmetric with regard to the pitch axis of the airfoil blade;
the airfoil blade having a leading edge and a rear edge, and the control cuff having a C-shaped profile in a plane perpendicular to the pitch axis of the airfoil blade, the C-shaped profile enclosing the airfoil blade, the C-shaped profile having a closed portion at the leading edge of the airfoil blade and a pair of rear portions towards the rear edge of the airfoil blade, the main bolt and the supporting bolt of the removable fasteners passing through the pair of rear portions of the control cuff.

2. The blade attachment according to claim 1 , wherein the main bolt has a greater diameter than the supporting bolt.

3. The blade attachment according to claim 2 , wherein the main bolt is arranged in the area of a 10-30% chord of a profile section of the airfoil blade, respectively slightly in front of the pitch axis towards a leading edge of the profile section.

4. The blade attachment according to claim 2 , wherein the main bolt is hollow.

5. The blade attachment according to claim 2 , wherein the main bolt or the supporting bolt together with any screw nuts are integrated aerodynamically into respectively associated corrugations of the profile section of the control cuff.

6. The blade attachment according to claim 2 , wherein the flexbeam head is prepared for reception of the main bolt for connecting the flexbeam head to the root end of the airfoil blade and the control cuff is prepared for reception of the supporting bolt for connecting the root end of the airfoil blade to the control cuff.

7. The blade attachment according to claim 1 , wherein a fastener mechanically connects the control cuff to the flexbeam.

8. The blade attachment according to claim 1 , wherein the control cuff is formed with a rear slit adjacent to the flexbeam head.

9. A blade attachment for a bearingless rotor of a helicopter, comprising:
a flexbeam having a flexbeam body and a fork-shaped flexbeam head at a distal end of the flexbeam body;
a control cuff extending about a portion of the flexbeam;
a first bolt configured to couple the flexbeam head and control cuff to a root of an airfoil blade while being positioned generally perpendicular to a lead-lag pivoting plane and spaced a first distance from a blade pitch axis;
a second bolt configured to couple the control cuff to a root of an airfoil blade while being positioned generally perpendicular to a lead-lag pivoting plane and spaced a second distance from a blade pitch axis, wherein the first distance is different from the second distance; and
the airfoil blade having a leading edge and a rear edge, and the control cuff having a C-shaped profile in a plane perpendicular to the pitch axis of the airfoil blade, the C-shaped profile enclosing the airfoil blade, the C-shaped profile having a closed end at the leading edge of the airfoil blade and a pair of rear ends towards the rear edge of the airfoil blade, the first and second bolts passing through the pair of rear ends.

10. The blade attachment of claim 9 , wherein the fork-shaped flexbeam head has an upper flange and a lower flange, and wherein at the distal end the upper flange and lower flange each extend from a respective first side to a respective second side with an uninterrupted gap therebetween.

11. The blade attachment of claim 9 , wherein the first bolt has a first diameter and the second bolt has a second diameter, the first diameter being different from the second diameter.

12. The blade attachment of claim 9 , wherein the second bolt does not couple the flexbeam head to the control cuff.

13. The blade attachment of claim 9 , wherein the rotor blade extends from the blade root to a blade tip and defines the pitch axis, the blade root being coupled to the flexbeam head and control cuff by the first bolt and coupled to the control cuff by the second bolt.

14. The blade attachment of claim 13 , wherein the blade has a chord extending from a leading edge to a trailing edge, the first bolt being disposed between the pitch axis and the leading edge in a region between 10% and 30% chord.

15. A rotorcraft comprising: a main rotor having a rotor head;
a flexbeam having a first end and a second end, the first end being coupled to the rotor head and the second end having a fork-shaped flexbeam head;
a control cuff extending about a portion of the flexbeam;
an airfoil blade having a blade root and a blade tip, the blade having a pitch axis extending from the blade root to the blade tip and defining a lead-lag pivoting plane;
a first bolt coupling the flexbeam head and control cuff to the blade root, the first bolt being generally perpendicular to the lead-lag pivoting plane and spaced a first distance from the pitch axis;
a second bolt coupling the control cuff to the blade root, the second bolt being generally perpendicular to the lead-lag pivoting plane and spaced a second distance from the pitch axis, wherein the first distance is different from the second distance; and
the airfoil blade having a leading edge and a rear edge, and the control cuff having a C-shaped profile and enclosing the airfoil blade, the C-shaped profile having a closed end at the leading edge of the airfoil blade and an open end having a pair of rear portions adjacent the rear edge of the airfoil blade, the first and second bolts passing through the pair of rear portions of the control cuff.

16. The rotorcraft of claim 15 , wherein the first bolt has a first diameter and the second bolt has a second diameter, the first diameter being different from the second diameter.

17. The rotorcraft of claim 15 , wherein the blade has a leading edge, the blade root has a chord length, and the pitch axis passes through the blade root at 25% of the chord length from the leading edge.

18. The rotorcraft of claim 15 , wherein the blade has a leading edge, the blade root has a chord length, and the first bolt being disposed between the pitch axis and the leading edge in a region between 10% and 30% of the chord length.

19. The rotorcraft of claim 15 , wherein the second bolt does not couple the flexbeam head to the control cuff and blade root.

20. The rotorcraft of claim 15 , wherein the fork-shaped flexbeam head has an upper flange and a lower flange, and wherein at the second end the upper flange and lower flange each have a face surface extending uninterrupted and transversely relative to the flexbeam from a respective first side surface to a respective second side surface.

Assignees

• Airbus Helicopters Deutschland GmbH

Inventors

• Kuntze-Fechner Gerald
• Bauer Markus
• Ortner Martin

Classifications

• B64C27/33

  having flexing arms · CPC title

• B64C27/50

  Blades foldable to facilitate stowage of aircraft · CPC title

• B64C27/48 Primary

  Root attachment to rotor head · CPC title

• B64C27/473

  Constructional features · CPC title