Aircraft having a lambda-box wing configuration

1. An aircraft comprising:

a fuselage,

a propulsion system,

a pair of swept-back airfoils, connected to a top forward portion of the fuselage,

a pair of swept-forward airfoils connected to a lower rear portion of the fuselage at a point of the fuselage aft of a connection of the swept-back airfoils,

a pair of substantially vertical airfoils,

wherein the tips of the swept-forward airfoils are connected to a lower side of the swept-back airfoils at an intermediate point of a span of the swept-back airfoils by the substantially vertical airfoils, the swept-back airfoils having a higher aspect ratio than that of the swept-forward airfoils, which makes the swept-back airfoils have a reduced induced drag without penalizing their weight, as their maximum bending moment is reduced because of structural support that the swept-forward airfoils provide to the swept-back airfoils through the vertical airfoils, and

a landing gear system comprising at least one leg connected to a lower portion of the forward fuselage, and two legs connected to a lower side of the swept-forward airfoils, the at least two legs of the lower side of the swept-forward airfoils and the propulsion system being connected to a same structural spar of the swept-forward airfoils, so that the inertial loads introduced by the propulsion system in cases of landing with high vertical accelerations are transmitted to the landing gear legs through a shortest possible load path within an airframe as allowed by landing gear legs separation and engine installation requirements.

2. The aircraft according to claim 1 , wherein the swept-back airfoils and the swept-forward airfoils have sweep angles providing a horizontal separation between said swept-back airfoils and swept-forward airfoils, this separation reducing compressible drag of the aircraft flight at high speeds due to aerodynamic interaction of the swept-back airfoils and swept-forward airfoils.

3. The aircraft according to claim 1 or 2 , wherein horizontal stagger of the swept-back airfoils and swept-forward airfoils provides sufficient longitudinal stability and control to the aircraft without the need of a horizontal stabilizer.

4. The aircraft according to claim 1 , wherein a center of lift of the swept-back airfoils is located forward of a center of gravity of the aircraft, the center of lift of the swept-forward airfoils being located behind the center of gravity of the aircraft, this configuration helping to provide static stability to the aircraft.

5. The aircraft according to claim 1 , wherein the propulsion system is located on an upper side of the swept-forward airfoils such that noise radiated downwards by exhaust gases of the propulsion system intercepts the swept-forward airfoils, which act as noise shields reducing perceived noise between the engines and the ground during aircraft flight.

6. The aircraft according to claim 5 , wherein the noise radiated by the exhaust gases of the propulsion system and emitted downwards at an angle between 30° and 70°, this angle being measured from an axis of symmetry of an exhaust jet, intersects the upper side of the swept-forward airfoils which thereby act as noise shields.

7. The aircraft according to claim 1 , wherein the propulsion system comprises at least two engines of turbojet, turbofan, turboprop or unducted fan type.

8. The aircraft according to claim 1 , wherein the swept-back airfoils comprise control surfaces located at an inboard portion of said swept-back airfoils and adjacent to the fuselage such that these control surfaces are able to deflect downwards in order to produce a pitch-up moment during a take-off run to assist aircraft rotation for lift-off.

9. The aircraft according to claim 1 , wherein the swept-forward airfoils comprise control surfaces located at an inboard portion of the swept-forward airfoils adjacent to the fuselage, these control surfaces being able to deflect upwards in order to produce a pitch-up moment during a take-off run to assist aircraft rotation for lift-off.

10. The aircraft according to claim 1 , wherein the swept-forward airfoils provide aerodynamic forces in an upwards direction during a cruise portion of flight of the aircraft.

11. The aircraft according to claim 1 , wherein the swept-back airfoils comprise trailing edge control surfaces that provide roll control to the aircraft.

12. The aircraft according to claim 1 , further comprising:

a retractable passenger staircase located at a rear lower portion of the fuselage to allow access to an interior of the aircraft without aid of ground equipment.

13. The aircraft according to claim 1 , further comprising:

a pair of airfoils connected to a rear portion of the fuselage, the airfoils providing additional static longitudinal stability and also longitudinal control to the aircraft by being able to rotate around an axis perpendicular to a plane of symmetry of the aircraft.

14. The aircraft according to claim 1 , further comprising:

a pair of airfoils connected to a forward portion of the fuselage, the airfoils providing additional static longitudinal stability and also longitudinal control to the aircraft by being able to rotate around an axis perpendicular to a plane of symmetry of the aircraft.