Tilting hexrotor aircraft

1. An aircraft comprising:

a fuselage;

a wing connected to the fuselage;

first and second booms connected to the wing on opposite sides of the fuselage;

no more than six propulsion systems, the propulsion systems including:

first and second forward propulsion systems tiltably connected to forward ends of the first and second booms such that the first and second forward propulsion systems are tiltable between a first position when the aircraft is in a hover mode in which the first and second forward propulsion systems rotate in a horizontal plane and a second position when the aircraft is in a cruise mode;

first and second aft propulsion systems fixedly attached proximate aft ends of the first and second booms, wherein each of the aft propulsions systems is angled outboard from a top surface of the one of the booms to which it is attached such that an axis of rotation of the aft propulsion system forms a non-zero angle outboard from a vertical axis; and

first and second wing-mounted propulsion systems connected to outboard ends of wings;

wherein the first and second wing-mounted propulsion systems are tiltable between a first position when the aircraft is in the hover mode and a second position when the aircraft is in the cruise mode;

wherein each of the first and second aft propulsion systems includes a rotor mast and a fairing configured to surround the rotor mast;

wherein each of a height of the fairings relative to a radius of the aft propulsion systems and a width of the fairings relative to a width of the booms is configured to minimize rotor-boom noise; and

wherein each of the propulsion systems includes a rotor assembly comprising a plurality of rotor blades.

2. The aircraft of claim 1 , wherein the rotor assemblies of the first and second aft propulsion systems rotate when the aircraft is in the hover mode and cease to rotate when the aircraft is in the cruise mode.

3. The aircraft of claim 1 , wherein the rotor assemblies of the first and second forward propulsion systems rotate when the aircraft is in the hover mode and cease to rotate when the aircraft is in the cruise mode.

4. The aircraft of claim 1 , wherein the rotor assemblies of the forward propulsion systems and the wing-mounted propulsion systems include an identical number of blades.

5. The aircraft of claim 4 , wherein the rotor assemblies of the aft rotor propulsion systems include fewer blades than the rotor assemblies of the forward propulsion systems and the wing-mounted propulsion systems.

6. The aircraft of claim 1 , wherein the rotor assemblies of the forward propulsion systems and the wing-mounted propulsion systems include five blades each and the rotor assemblies of the aft rotor propulsion systems include two blades each.

7. The aircraft of claim 1 , wherein the wing is disposed on a top surface of the fuselage.

8. The aircraft of claim 1 , wherein a portion of each of the booms is integrated into the wing.

9. The aircraft of claim 1 , wherein the propulsion systems collectively comprise a hexrotor arc when the aircraft is in the hover mode.

10. The aircraft of claim 1 , wherein the first and second forward propulsion systems are located forward of the first and second wing-mounted propulsion systems.

11. The aircraft of claim 1 , wherein the first and second wing-mounted propulsion systems are located outboard of the first and second forward propulsion systems.

12. The aircraft of claim 1 , wherein the first and second aft propulsion systems are attached to a top surface of the first and second booms such that the rotor assemblies rotate above the first and second booms.

13. An electric vertical takeoff and landing aircraft (eVTOL) selectively convertible between a hover mode and a cruise mode, the eVTOL comprising:

a fuselage;

a wing connected to the fuselage and having opposite outboard ends;

first and second booms connected to the wing on opposite sides of the fuselage and including forward ends disposed forward of the wing and aft ends disposed aft of the wing; and

a propulsion arrangement for propelling the aircraft, the propulsion arrangement comprising no more than six propulsion systems, the no more than six propulsion systems comprising:

first and second forward propulsion systems attached to the forward ends of the first and second booms;

first and second aft propulsion systems fixedly attached proximate the aft ends of the first and second booms, wherein each of the first and second aft propulsion systems includes a rotor mast for supporting a rotor assembly of the aft propulsion system and a fairing configured to surround the rotor mast between the rotor assembly and the respective one of the first and second booms, and wherein each of a height of the fairings relative to a radius of the aft propulsion systems and a width of the fairings relative to a width of the booms is configured to minimize rotor-boom noise; and

first and second wing-mounted propulsion systems connected to outboard ends of wings, wherein each of the first and second wing-mounted propulsion systems includes a pylon for housing a drive system;

wherein each of the pylons is tiltable relative to the wing between a first position when the aircraft is in a hover mode and a second position when the aircraft is in a cruise mode.

14. The eVTOL of claim 13 , wherein the first and second aft propulsion systems are operable when the aircraft is in the hover mode and inoperable when the aircraft is in the cruise mode.

15. The eVTOL of claim 13 , wherein the first and second forward propulsion systems are tiltably connected to forward ends of the first and second booms such that the first and second forward propulsion systems are tiltable between a first position when the aircraft is in the hover mode and a second position when the aircraft is in the cruise mode.

16. The eVTOL of claim 13 , wherein the first and second forward propulsion systems are fixedly attached to the forward ends of the first and second booms and wherein the first and second forward propulsion systems are operable when the aircraft is in the hover mode and inoperable when the aircraft is in the cruise mode.

17. The eVTOL of claim 13 , wherein the propulsion systems collectively comprise a hexrotor arc when the aircraft is in the hover mode.

18. The eVTOL of claim 13 , wherein the first and second aft propulsion systems are attached to a bottom surface of the first and second booms such that rotor assemblies of the first and second aft propulsion systems rotate below the first and second booms.

19. An electric vertical takeoff and landing aircraft (eVTOL) selectively convertible between a hover mode and a cruise mode, the eVTOL comprising:

a fuselage;

a wing connected to a top surface of the fuselage and having opposite outboard ends;

first and second booms connected to the wing on opposite sides of the fuselage and including forward ends disposed forward of the wing and aft ends disposed aft of the wing;

first and second forward propulsion systems attached to the forward ends of the first and second booms;

first and second aft propulsion systems fixedly attached proximate the aft ends of the first and second booms, wherein each of the aft propulsions systems is angled outboard from a top surface of the one of the booms to which it is attached such that an axis of rotation of the aft propulsion system forms a non-zero angle outboard from a vertical axis; and

first and second wing-mounted propulsion systems connected to outboard ends of wings, wherein each of the first and second wing-mounted propulsion systems includes a pylon for housing a drive system;

wherein each of the pylons is tiltable relative to the wing between a first position when the aircraft is in a hover mode and a second position when the aircraft is in a cruise mode;

wherein each of the first and second aft propulsion systems includes a rotor mast and a fairing configured to cover the rotor mast; and

wherein each of a height of the fairings relative to a radius of the aft propulsion systems and a width of the fairings relative to a width of the booms is configured to minimize rotor-boom noise.