Vertical take off aircraft

1. An aircraft, comprising:

a fuselage having a nose end and a second, opposing end defined as a tail end;

a wing coupled to the fuselage between the nose end and the tail end;

a propulsion unit coupled to the fuselage and disposed proximal the tail end; and

a controller configured to control the aircraft in:

a vertical flight mode in which a first lifting force generated by the propulsion unit is greater than a second lifting force generated by the wing,

a horizontal flight mode in which the second lifting force is greater than the first lifting force, and

a transition flight mode in which the aircraft transitions from the vertical flight mode to the horizontal flight mode, wherein

in the transition flight mode, the controller is operable to:

accelerate the aircraft until a sensed airspeed exceeds a threshold, and

orient the aircraft based on trajectory commands by comparing sensor inputs to a desired orientation.

2. The aircraft of claim 1 , wherein the propulsion unit is configured to provide directed thrust.

3. The aircraft of claim 1 , wherein, in the transition flight mode, the aircraft is configured to determine a ground speed acceleration rate and accelerate the aircraft at the ground speed acceleration rate.

4. The aircraft of claim 1 , wherein the threshold is above the stall speed by a margin.

5. The aircraft of claim 1 , wherein the propulsion unit includes a ducted fan.

6. The aircraft of claim 5 , wherein the propulsion unit includes a plurality of control vanes to provide directed thrust.

7. The aircraft of claim 1 , wherein the controller is configured to

generate commands for pitch, speed and roll based at least in part on sensory input values for speed, position and altitude, and

determine Euler angle errors based on the sensory input values and the trajectory commands.

8. The aircraft of claim 7 , wherein the controller is configured to determine body axis angle errors based on the Euler angle errors.

9. The aircraft of claim 1 , wherein the controller is configured to transition the aircraft from the vertical flight mode to the horizontal flight mode while maintaining altitude of the aircraft within 100 ft throughout the transition.

10. The aircraft of claim 1 , wherein the controller is configured to transition the aircraft from the horizontal flight mode to the vertical flight mode.

11. The aircraft of claim 10 , wherein the controller is configured to transition the aircraft from the horizontal flight mode to the vertical flight mode while maintaining altitude of the aircraft within 100 ft throughout the transition.

12. The aircraft of claim 1 , wherein a center of gravity of the aircraft is disposed in a location such that the aircraft balances at rest in an orientation where the nose end is positioned over the duct.

13. A method of transitioning an aircraft that includes a fuselage, a propulsion unit and a wing, wherein the fuselage includes a nose end and a second, opposing end defined as a tail end, the propulsion unit is coupled to the fuselage and disposed proximal the tail end, and the wing is coupled to the fuselage, the method comprising:

flying the aircraft in a vertical flight mode in which a first lifting force generated by the propulsion unit is greater than a second lifting force generated by the wing;

adjusting an output power of the propulsion unit and a pitching moment of the aircraft to accelerate the aircraft in a horizontal direction, the adjusting including accelerating the aircraft until a sensed airspeed exceeds a threshold;

flying the aircraft in a horizontal flight mode in which the second lifting force is greater than the first lifting force; and

flying the aircraft at an orientation based on trajectory commands by comparing sensor inputs to a desired orientation.

14. The method of claim 13 , wherein the propulsion unit includes a ducted fan.

15. The method of claim 13 , wherein the propulsion unit includes a plurality of control vanes to provide directed thrust, and the adjusting includes adjusting a position of the control vanes.

16. The method of claim 13 , further comprising determining Euler angle errors based on sensory input values and the trajectory commands.

17. The method of claim 16 , further comprising determining body axis angle errors based on the Euler angle errors.

18. The method of claim 17 , wherein the flying the aircraft in the vertical flight mode, the adjusting, and the flying the aircraft in the horizontal mode are performed maintaining altitude of the aircraft within 100 feet.

19. The method of claim 13 , further comprising adjusting, after the flying the aircraft in a horizontal flight, the output power and pitch moment of the controllable vanes to decelerate the aircraft in the horizontal direction until the first lifting force is greater than the second lifting force.

20. The method of claim 13 , further comprising maintaining trim of the aircraft at any angle of attack between zero degrees and ninety degrees.