Ducted proprotor systems having adaptive duct geometries

1. A proprotor system for a ducted aircraft convertible between a vertical takeoff and landing flight mode and a forward flight mode comprising:

a plurality of proprotor blades;

a duct surrounding the proprotor blades and including an adaptive geometry device movable into a plurality of positions including a hover position and a cruise position, the adaptive geometry device comprising leading edge adaptive geometry devices including a plurality of hinged noses slidably coupled to a leading edge of the duct, the hinged noses substantially in chordwise alignment with the duct in the cruise position and tilted radially outward to increase a leading edge inner lip radius of the duct in the hover position; and

one or more actuators coupled to the adaptive geometry device;

wherein, the hinged noses are slidable along the leading edge of the duct to move between the hover position and the cruise position; and

wherein, the one or more actuators are configured to move the adaptive geometry device between the hover position and the cruise position based on the flight mode of the ducted aircraft, thereby improving flight performance of the ducted aircraft.

2. The proprotor system as recited in claim 1 wherein the duct forms a shape and movement of the adaptive geometry device between the hover position and the cruise position changes the shape of the duct.

3. The proprotor system as recited in claim 1 wherein the adaptive geometry device further comprises a trailing edge adaptive geometry device coupled to a trailing edge of the duct.

4. The proprotor system as recited in claim 3 wherein the trailing edge adaptive geometry device further comprises a plurality of plain flaps rotatably coupled to the trailing edge of the duct; and

wherein, the plain flaps are substantially in chordwise alignment with the duct in the cruise position and tilted radially outward to increase a diffusion angle of the duct in the hover position.

5. The proprotor system as recited in claim 3 wherein the trailing edge adaptive geometry device further comprises a plurality of Fowler flaps slidably coupled to the trailing edge of the duct; and

wherein, the Fowler flaps are retracted against an inner surface of the duct in the cruise position and extended aftward and radially outward to increase a diffusion angle of the duct in the hover position.

6. The proprotor system as recited in claim 1 wherein the adaptive geometry device further comprises an intermediate adaptive geometry device disposed between leading and trailing edges of the duct.

7. The proprotor system as recited in claim 6 wherein the duct further comprises a plurality of tail extensions and a forward duct airframe and the intermediate adaptive geometry device further comprises a plurality of elongating adaptive geometry devices slidably coupling the tail extensions to the forward duct airframe.

8. The proprotor system as recited in claim 7 wherein the elongating adaptive geometry devices extend the tail extensions in an aft direction in the hover position and retract the tail extensions toward the forward duct airframe in the cruise position.

9. The proprotor system as recited in claim 1 wherein the adaptive geometry device further comprises a plurality of adaptive geometry devices circumferentially disposed around a circumference of the duct.

10. The proprotor system as recited in claim 1 wherein the adaptive geometry device further comprises a plurality of adaptive geometry devices and the one or more actuators further comprise a plurality of actuators, each actuator coupled to a respective one of the adaptive geometry devices.

11. The proprotor system as recited in claim 1 wherein the one or more actuators move the adaptive geometry device into the hover position in the vertical takeoff and landing flight mode and the cruise position in the forward flight mode.

12. A ducted aircraft comprising:

a fuselage;

a proprotor system coupled to the fuselage, the proprotor system comprising:

a plurality of proprotor blades;

a duct surrounding the proprotor blades and including an adaptive geometry device movable into a plurality of positions including a hover position and a cruise position, the adaptive geometry device comprising leading edge adaptive geometry devices including a plurality of hinged noses slidably coupled to a leading edge of the duct, the hinged noses substantially in chordwise alignment with the duct in the cruise position and tilted radially outward to increase a leading edge inner lip radius of the duct in the hover position; and

one or more actuators coupled to the adaptive geometry device;

wherein, the ducted aircraft is convertible between a vertical takeoff and landing flight mode and a forward flight mode;

wherein, the hinged noses are slidable along the leading edge of the duct to move between the hover position and the cruise position; and

wherein, the one or more actuators are configured to move the adaptive geometry device between the hover position and the cruise position based on the flight mode of the ducted aircraft, thereby improving flight performance of the ducted aircraft.

13. The ducted aircraft as recited in claim 12 wherein the duct has a leading edge inner lip radius R when the adaptive geometry device is in the hover position and a leading edge inner lip radius r when the adaptive geometry device is in the cruise position; and

wherein, R>r.

14. The ducted aircraft as recited in claim 12 wherein the duct has a chord length L when the adaptive geometry device is in the hover position and a chord length l when the adaptive geometry device is in the cruise position; and

wherein, L>l.

15. The ducted aircraft as recited in claim 12 wherein the duct has a diffusion angle A when the adaptive geometry device is in the hover position and a diffusion angle α when the adaptive geometry device is in the cruise position; and

wherein, A>α.

16. The ducted aircraft as recited in claim 12 wherein the duct has a thickness T when the adaptive geometry device is in the hover position and a thickness t when the adaptive geometry device is in the cruise position; and

wherein, T>t.

17. The ducted aircraft as recited in claim 12 further comprising a flight control computer including a duct geometry controller configured to detect the flight mode of the ducted aircraft and send one or more commands to the one or more actuators to move the adaptive geometry device based on the flight mode of the ducted aircraft.

18. The proprotor system as recited in claim 1 wherein aft ends of the hinged noses form curved surfaces contouring a curved leading edge of the duct.

19. The proprotor system as recited in claim 1 wherein aft ends of the hinged noses form concave surfaces and the leading edge of the duct forms a convex surface complementary to the aft concave surfaces of the hinged noses.