METHOD OF IMPROVING A STABILITY SPEED OF A TILTROTOR AIRCRAFT

• US 20200130813A1
• Filed: 10/24/2018
• Published: 04/30/2020
• Est. Priority Date: 10/24/2018
• Status: Active Grant

• Current Assignee: Bell Textron Rhode Island Inc. (Textron Inc)
• Original Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Inventors: CHOI, Jouyoung Jason, STAMPS, Frank
• Granted Patent: US 10,960,969 B2
• Time in Patent Office: Days
• CPC Class Codes: B64C 11/008 characterised by vibration absorbing or balancing means
• CPC Class Codes: B64C 11/06 for variable-pitch blades
• CPC Class Codes: B64C 11/32 mechanical
• CPC Class Codes: B64C 29/0033 the propellers being tiltable relative to the fuselage

Abstract

A method of increasing a stability speed of a tiltrotor aircraft includes pivoting a rotor assembly having at least three rotor blades from a first position for operating the tiltrotor aircraft in a helicopter mode to a second position for operating the tiltrotor aircraft in an airplane mode, and increasing a stiffness of the rotor assembly when the rotor assembly is in the second position.

Claims

1. A method of increasing a stability speed of a tiltrotor aircraft, the method comprising:

pivoting a rotor assembly of the tiltrotor aircraft from a first position for operating the tiltrotor aircraft in a helicopter mode to a second position for operating the tiltrotor aircraft in an airplane mode; and

increasing a stiffness of the rotor assembly when the rotor assembly is in the second position, wherein the rotor assembly comprises at least four rotor blades.

2. The method of claim 1, wherein the increasing the stiffness of the rotor assembly comprises locking a yoke of the rotor assembly so that the yoke cannot gimbal about a mast of the rotor assembly.

3. The method of claim 2, wherein the locking the yoke comprises moving a gimbal lock into contact with the yoke.

4. The method of claim 3, wherein the gimbal lock comprises a sloped surface configured to mate with a lip of an opening in the yoke.

5. The method of claim 3, wherein the moving is performed by an actuator that is coupled to the gimbal lock.

6. The method of claim 5, wherein the actuator is controlled by a flight control computer.

7. The method of claim 6, wherein the flight control computer activates the actuator when the rotor assembly is in the second position.

8. The method of claim 6, wherein the flight control computer monitors one or more sensors and activates the actuator responsive to determination that the rotor assembly is stable.

9. The method of claim 8, wherein the one or more sensors comprise a first sensor located proximate to a wing of the tiltrotor aircraft and a second sensor located proximate the rotor assembly, the first sensor configured to monitor bending within the wing and the second sensor configured to monitor vibrations in the rotor assembly.

10. The method of claim 1, wherein prior to the increasing the stiffness of the rotor assembly, a speed of an engine coupled to the rotor assembly is decreased.

11. The method of claim 1, wherein the stiffness of the rotor assembly in the second position is at least an order of magnitude greater than the stiffness of the rotor assembly in the first position.

12. The method of claim 1, wherein, when the rotor assembly is in the second position, a flap center of each rotor blade of the at least four rotor blades is located at a distance radially outward from the flap center of each rotor blade of the at least four rotor blades when the rotor assembly is in the first position.

13. The method of claim 1, wherein the increasing the stiffness the rotor assembly decreases a delta-3 of the rotor assembly.

14. A method of increasing a stability speed of a tiltrotor aircraft, the method comprising:

pivoting a rotor assembly of the tiltrotor aircraft from a first position for operating the tiltrotor aircraft in a helicopter mode to a second position for operating the tiltrotor aircraft in an airplane mode, the rotor assembly comprising at least four rotor blades; and

moving, during flight, flap centers of each of the at least four rotor blades radially outward from a mast of the rotor assembly to lower a delta-3 of the rotor assembly when the rotor assembly is in the second position.

15. The method of claim 14, wherein the moving the flap centers of each of the at least four rotor blades comprises locking a yoke of the rotor assembly so that the yoke cannot gimbal about a mast of the rotor assembly.

16. The method of claim 15, wherein the locking the yoke comprises moving a gimbal lock into contact with the yoke.

17. The method of claim 16, wherein the moving is performed by an actuator that is coupled to the gimbal lock.

18. The method of claim 17, wherein:

the actuator is controlled by a flight control computer; and

the flight control computer activates the actuator when the rotor assembly is in the second position.

19. The method of claim 18, wherein:

the flight control computer monitors one or more sensors; and

the one or more sensors comprise a first sensor located proximate to a wing of the tiltrotor aircraft and a second sensor located proximate the rotor assembly, the first sensor configured to monitor bending within the wing and the second sensor configured to monitor vibrations in the rotor assembly.

20. The method of claim 14, wherein a stiffness of the rotor assembly in the second position is at least an order of magnitude greater than the stiffness of the rotor assembly in the first position.