FIXED-WING AIRCRAFT WITH INCREASED STATIC STABILITY

Abstract

The invention relates to an aircraft having at least one wing (5) including, at each end thereof, a fin (6) forming an angle of between 0? and 45? relative to the vertical. According to the invention, each fin (6) has a leading edge (7) that includes at least one slot (8) provided along said leading edge (7) and oriented so as to cause an air flow to flow via said leading edge (7) from an outer surface (6a) of the fin (6) to an inner surface (6b).

Claims

1. An aircraft (1) having at least one wing (5) comprising, at each of the ends thereof, a winglet (6) forming an angle of between 0? and 45? relative to the vertical, characterized in that each winglet (6) has a leading edge (7) that comprises at least one slot (8) placed along said leading edge (7) and oriented so as to make an airflow circulate through said leading edge (7) from an outer surface (6a) of the winglet (6) to an inner surface (6b) of said winglet (6).

2. The aircraft (1) according to claim 1, characterized in that the leading edge (7) of each winglet (6) comprises at least two parallel slots (8).

3. The aircraft (1) according to claim 1, characterized in that each winglet (6) comprises at least one fixed slat (9) situated in front of the leading edge (7), forming at least one fixed surface separated from the leading edge (7) so as to place said at least one slot (8) between said fixed surface and the leading edge (7).

4. The aircraft (1) according to claim 3, characterized in that the slat (9) is installed retractably in order to block the slot (8).

5. The aircraft (1) according to claim 1, characterized in that each winglet (6) comprises at least one flap mounted movably in order to block the slot or slots (8).

6. The aircraft (1) according to claim 1, characterized in that it comprises at least one fuselage (3) and one vertical stabilizer (10).

7. The aircraft (1) according to claim 6, characterized in that each winglet (6) is connected to the vertical stabilizer (10) of the fuselage (3) by means of a wing portion (11).

8. The aircraft (1) according to claim 1, characterized in that each winglet (6) is inclined towards the rear of said aircraft (1).

9. The aircraft (1) according to claim 8, characterized in that each winglet (6) is inclined towards the rear of the aircraft (1) at an angle of between 45? and 65? relative to the vertical.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] Other characteristics and advantages of the invention will be seen clearly from the following description, provided by way of example and in no way limiting, with reference to the appended figures in which:

[0033] FIG. 1 is a perspective view of the aircraft according to the invention,

[0034] FIG. 2 is a detailed view of the vertical winglet of the aircraft according to the invention, viewed from the inner side, said winglet comprising two slots along its leading edge,

[0035] FIG. 3 is a view similar to the one in FIG. 2, the winglet being viewed from the outer side,

[0036] FIG. 4 is a view similar to the one in FIG. 2, the winglet being viewed from above and in transverse section,

[0037] FIG. 5 is a view similar to the one in FIG. 4, illustrating another embodiment of the invention, the winglet comprising a retractable slat with single slot,

[0038] FIG. 6 is a detailed view of the winglet according to the embodiment of FIG. 5, viewed from the inner side with the retractable slat in the open position,

[0039] FIG. 7 is a view similar to the one in FIG. 6 with the retractable slat in the closed position.

DETAILED DESCRIPTION OF THE INVENTION

[0040] With reference to FIG. 1, the invention is described in relation to a pilotless aircraft (1), commonly called drone, consisting of a central fuselage (2) and two lateral fuselages (3) extending parallel to the central fuselage (2), and carrying respectively, preferably, a means of propulsion (not shown). Said lateral fuselages (3) are connected to the central fuselage (2) by a wing (4) inclined from front to rear. The central fuselage (2) has a length that is less than the length of the lateral fuselages (3).

[0041] Moreover, according to the embodiment illustrated in FIG. 1, the aircraft (1) also comprises two substantially horizontal wings (5) extending laterally from said lateral fuselages (3). It will be noted that the aircraft (1) may not include a central fuselage (2) without, however, going beyond the scope of the invention.

[0042] Each means of propulsion consists of a motor, not shown in the figures, driving a propeller (not shown) positioned at the front of each lateral fuselage (3). Furthermore, the axis of each propeller forms for example an angle, in the vertical plane, with the plane of the horizontal wings (4) and/or said horizontal wings (4) comprising flaps with single or double or triple slot in order to obtain a so-called blown wing. Thus, the propellers blow directly onto nearly all of the wings and greatly increase the lift in this area.

[0043] In this way, the illustrated aircraft (1) has a very high lift coefficient enabling takeoff over a very short distance, for example on the order of 90 m.

[0044] Moreover, each horizontal lateral wing (5) comprises, at the free end thereof, a winglet (6) extending upwards and defining in particular an angle of between 0? and 45?, and preferably between 1? and 15? relative to the vertical. Each winglet (6) is, for example, inclined towards the rear of the aircraft (1) at an angle of between 45? and 65? and preferably 55? relative to the vertical.

[0045] According to the invention, each winglet (6) has a leading edge (7) that comprises at least one slot (8) placed along each leading edge (7) and oriented to make an airflow circulate through said leading edge (7) from an outer surface (6a) of the winglet (6) to an inner surface (6b). According to the illustrated embodiment, each winglet (6) comprises two slots (8) called parallel longitudinal.

[0046] In this way, the passage of an airflow through said slots (8) makes it possible to generate a lift on the winglets (6) that has a vertical component that increases with the incidence of the horizontal wings (4, 5). Said additional lift makes it possible to stabilize the aircraft (1) and to increase the angle at which the horizontal wings (4, 5) stall. Furthermore, the transverse section of the slots (8) is advantageously concave, in such a way that said slots (8) define an additional leading edge (7a) that is curved, and they form a wing profile to generate the lift during the flow of air.

[0047] According to a particular embodiment illustrated in FIGS. 5 to 7, each winglet (6) comprises a fixed slat (9) situated in front of the leading edge (7). The fixed slat (9) forms at least one fixed surface separated from the leading edge (7) of the winglet (6) so as to place a slot (8) between said fixed surface and the leading edge (7). The slat (9) is installed retractably to change from a position blocking to a position clearing the slot (8), and to avoid creating an additional parasitic drag that wastes the power of the aircraft (1). It is also possible to achieve this function by means of a flap mounted pivotably on each winglet (6) between a position blocking and a position clearing the slots (8).

[0048] According to the embodiment illustrated in FIG. 1, the two lateral fuselages (3) each comprise a vertical stabilizer (10) and each winglet (6) is connected to the vertical stabilizer (10) of the respective lateral fuselage (3) by means of a wing portion (11), preferably extending substantially parallel to the horizontal wings (4). Said wing portion (11) extends from front to rear, forming an angle with the frontal plane of the aircraft (1). In this particular embodiment, the ratio of the height of the winglets (6) to the span of the aircraft (1) is between 0.15 and 0.25, and preferably equal to 0.2. Span is understood as the distance separating the ends of the two horizontal lateral wings (5).

[0049] It is quite obvious that this embodiment is a preferred embodiment of the invention. The essence of the invention is the presence of slots (8) placed in the winglets (6) extending upwards and arranged at the ends of the lateral wings (5) of the aircraft (1). For example, simple winglets (a term known to a person skilled in the art) with slots (8) fall within the scope of the present invention.

[0050] Moreover, it is obvious that the motors driving the propellers are of any appropriate type, such as preferably heat engines supplied by fuel stored in tanks placed in the lateral fuselages (3) and the horizontal wings (4, 5), or electric motors, without going beyond the scope of the invention.

[0051] Lastly, it is clear that the examples that have just been given are only specific illustrations and are by no means limiting as concerns the scope of application of the invention.