Conversion spindle with dual ducted tiltrotors

1. A ducted-rotor aircraft comprising:

a fuselage;

a spindle that is coupled to the fuselage; and

first and second ducts that are coupled to the spindle, each duct including a rotor that is disposed in an opening that extends through the duct, each rotor having a plurality of blades;

wherein the first and second ducts define first and second interior duct spaces, respectively, that are configured to receive airflow therethrough and wherein no portion of the spindle extends into either of the first and second interior duct spaces;

wherein the spindle comprises:

a shaft that extends from a first end to an opposed second end;

first and second fittings that are configured to be disposed onto, and secured to, the first and second ends of the shaft; and

first and second attachment interfaces that are configured to be attachable to the first and second ducts, respectively; and

wherein the first attachment interface is disposed within the duct, and between an internal fore spar of the first duct and an internal aft spar of the first duct.

2. The ducted-rotor aircraft of claim 1 , wherein the first and second attachment interfaces comprise an open box shape.

3. The ducted-rotor aircraft of claim 1 , wherein the spindle is coupled to the fuselage such that the spindle is rotatable about a spindle axis that extends therethrough, and

wherein the first and second ducts exhibit equal rotational displacement when the spindle is rotated about the spindle axis.

4. The ducted-rotor aircraft of claim 3 , further comprising:

first and second bearings that rotatably couple the spindle to the fuselage, wherein the first bearing is coupled to the fuselage proximate to the first duct and the second bearing is coupled to the fuselage proximate to the second duct.

5. The ducted-rotor aircraft of claim 4 , wherein the first bearing is configured to react to radial loads and the second bearing is configured to react to both radial and axial loads.

6. The ducted-rotor aircraft of claim 3 , further comprising:

a conversion actuator that is coupled to the fuselage and the spindle, the conversion actuator operable to cause the spindle to rotate about the spindle axis.

7. The ducted-rotor aircraft of claim 1 , wherein the first and second attachment interfaces are integral with the first and second fittings, respectively.

8. The ducted-rotor aircraft of claim 1 , wherein the first and second fittings are configured to be secured to the first and second attachment interfaces with fasteners.

9. A duct assembly for a ducted-rotor aircraft, the duct assembly comprising:

first and second ducts, each duct including a rotor that is disposed in an opening that extends through the duct, the rotor having a plurality of blades; and

a spindle that is configured to support the first and second ducts,

wherein the first and second ducts are coupled to the spindle;

wherein no portion of the spindle extends into either the opening of either of the first and second ducts;

wherein the spindle comprises:

a shaft that extends from a first end to an opposed second end;

first and second fittings that are configured to be disposed onto, and secured to, the first and second ends of the shaft; and

first and second attachment interfaces that are configured to be attachable to the first and second ducts, respectively; and

wherein the first attachment interface is disposed within the duct, and between an internal fore spar of the first duct and an internal aft spar of the first duct.

10. The duct assembly of claim 9 , wherein the first attachment interface comprises an open box shape.

11. The duct assembly of claim 9 , wherein the first and second attachment interfaces are integral with the first and second fittings, respectively.

12. The duct assembly of claim 9 , wherein the first and second fittings are configured to be secured to the first and second attachment interfaces with fasteners.

13. The duct assembly of claim 10 , wherein each of the attachment interfaces comprises first and second planar surfaces that are spaced from each other, and

wherein the fore spar and the aft spar are annular and are configured to be attached to the respective first and second planar surfaces of the first attachment interface.

14. The duct assembly of claim 9 , further comprising:

first and second bearings that are mounted on the spindle and that are configured to rotatably couple the spindle to a fuselage of the aircraft,

wherein the first bearing is configured to react to radial loads and the second bearing is configured to react to both radial and axial loads.

15. A spindle for a ducted-rotor aircraft, the spindle comprising:

a shaft that extends from a first end to an opposed second end;

first and second fittings that are configured to be disposed onto, and secured to, the first and second ends of the shaft; and

first and second bearings that are mounted on the shaft and that are configured to rotatably couple the spindle to a fuselage of the aircraft,

wherein the first bearing is configured to react to radial loads and the second bearing is configured to react to both radial and axial loads;

wherein each of the first and second fittings includes a flange that is configured to be secured to a respective duct of the aircraft, wherein the flange is disposed within the duct, and between an internal fore annular spar of the first duct and an internal aft annular spar of the first duct, wherein each duct defines an interior space configured to receive airflow therethrough, and wherein no portion of the flanges are disposed in the interior spaces of the ducts.

16. The spindle of claim 15 , further comprising:

first and second attachment interfaces that are configured to be attachable to respective first and second ducts of the aircraft, wherein the first and second attachment interfaces comprise an open box shape.

17. The spindle of claim 16 , wherein the first and second attachment interfaces are integral with the first and second fittings, respectively.

18. The spindle of claim 16 , wherein the first and second attachment interfaces are secured to the first and second fittings, respectively, with fasteners.