WO2018145675A1

WO2018145675A1 - Tail sitter

Info

Publication number: WO2018145675A1
Application number: PCT/CZ2018/050004
Authority: WO
Inventors: Martin DRSTICKA
Original assignee: New Space Technologies s.r.o.
Priority date: 2017-02-09
Filing date: 2018-02-08
Publication date: 2018-08-16
Also published as: CZ201778A3; CZ307350B6

Abstract

Tail sitter aircraft, comprising a fuselage (4) and a pair of wings (5), each wing having a leading edge (50) and a trailing edge (55), wherein each of the wings (5) is provided with a propeller propulsion unit and a plurality of control tabs (21, 22, 23) arranged at the trailing edge (55) side, the plurality of control tabs comprising at least two pivotally attached control tabs (21, 22, 23) for controlling the direction of the air flowing from the propeller propulsion unit, the plurality of control tabs (21, 22, 23) being interconnected with a an actuating mechanism (20) for controlling the swinging of at least one of the control tabs (21, 22, 23).

Description

TAIL SITTER

FIELD OF THE INVENTION

Aircrafts, which are characterized by the ability to take off and to land in a perpendicular direction and in an upright position and which assume a horizontal cruising flight position after take-off, are generally referred to as tail sitters. The essential advantage of such aircraft type consist in its ability to take off and to land vertically without needing any runway or another special catapult system and without excluding the possibility of being operated as a fixed-wing aircraft, i.e. with the use of the lifting force caused by the forward airspeed and by the shape of the wings during a cruising flight. In general, a tail sitter aircraft does not undergo any alteration of its configuration during a flight or in connection with changing flight modes, which means that neither any changes to the mutual positions of the propulsion units and the aircraft itself nor any adjustment of the lifting surfaces in relation to the aircraft itself occur. BACKGROUND OF THE INVENTION

Both throughout the history of aviation and at the present time, several tail sitter aircraft types have been developed and tried out, the main differences between the individaal types consisting in the arrangement of the lifting surfaces, the number and arrangement of propulsion units and the way of controlling the flight of the aircraft in different flight modes. Such examples can be found both in the category of manned aircraft and in that of unmanned aerial vehicles. Different designs have always been based on the effort to provide a reliable manoeuvrability of the aircraft in any expected flight mode. This particularly applies to the following flight modes:

- stabilized flight mode during which a vertical position of the aircraft is maintained, - horizontal flight mode corresponding to the configuration of an aircraft having fixed lifting surfaces,

- transitory flight modes between the aforesaid two ones,

- safe vertical take-off and landing. SUMMARY OF THE INVENTION

The objective of the present invention is to provide a tail sitter aircraft that will be reliably controllable in any flight mode.

The above objective is fulfilled by providing a tail sitter aircraft comprising a fuselage and a pair of wings, each wing having a leading edge and a trailing edge, wherein each of the wings is provided with a propeller propulsion unit and a plurality of control tabs arranged at the trailing edge side, the plurality of control tabs comprising at least two pivotally attached control tabs for controlling the direction of the air flowing from the propeller propulsion unit, the plurality of control tabs being interconnected with a an actuating mechanism for controlling the swinging of at least one of the control tabs.

Preferably, the plurality of control tabs comprises a means, preferably a control rod, for interconnecting the control tabs and thereby synchronizing the swinging motion of the control tabs.

Also preferably, the axes of the swinging motion of the control tabs are parallel to the trailing edge of the respective wing and/or with the plane of rotation of the propeller of the propulsion unit.

According to an especially preferred embodiment, each, plurality of control tabs comprises a pair of outer control tabs and one central control tab arranged therebetween, the leading edge of the latter being aligned with the trailing edge of the respective wing.

Preferably, at least one of the control tabs of each plurality has an aerodynamic teardrop shape in a section extending from the leading edge to the respective trailing edge of that tab.

The tail sitter aircraft is preferably further provided with a central propulsion unit arranged in the symmetry plane of the aircraft. Such embodiment is especially preferred, because the central propulsion unit can be used for reducing the load caused by the weight of the aircraft assuming the vertical position when taking off or landing as well as for propelling the aircraft assuming the cruising (horizontal position), whereas the propeller propulsion units installed on the wings, which can be also advantageously used during take-off and landing or, as the case may be, during the transitions between the vertical and horizontal positions, can be disabled during the cruising (horizontal) flight mode, the propellers of the latter propulsion units being concealed within a slot between the respective wing and the respective plurality of control tabs when disabled.

Also preferably, the propeller propulsion unit and the plurality of control tabs are arranged in the proximal area of the respective wing, whereas the trailing edge of the distal area of the wing is provided with a pivotally attached roll-control aileron for controlling the rolling motion of the aircraft in flight.

Preferably, the control tab, which is arranged closest to the rotation axis of the propeller of the propulsion unit, has a length measured in a direction parallel to the trailing edge of the wing, said length ranging from 80 to 120 % of the diameter of the propeller. And it is also advantageous, when the propeller of the propeller propulsion unit is arranged on the respective wing in a manner enabling the propeller to be aligned with the trailing edge of the wing and/or concealed within a slot delimited by the trailing edge of the wing and the plurality of control tabs, when the propeller is disabled.

I may be also advantageous to provide the frontal area of the tail sitter aircraft with a pair of additional stabilisation surfaces. And it may be also advantageous to arrange the leading edge of the roll-control aileron at the same line as the leading edge of one of the control tabs.

EXPLANATION OF THE DRAWINGS

An exemplary embodiment of the present invention is schematically shown in the accompanying drawings, wherein Fig. 1 is a front view showing a tail sitter aircraft in its parking or launching position, Fig. 2 is a side view showing the tail sitter aircraft of Fig. 1, Fig. 3 is a plan view showing the tail sitter aircraft of Fig. 1, Fig. 4 shows a portion of a wing of the tail sitter aircraft where control tabs are situated and Figs. 5A and 5b show an exemplary plurality of control tabs for the tail sitter aircraft according to the invention.

EXEMPLARY EMBODIMENTS OF THE INVENTION

As particularly clearly illustrated in Figs. 1 to 3, an exemplary embodiment of the tail sitter aircraft comprises a fuselage 4 carrying a pair of front horizontal stabilizers 6 (so called duck wings) in its front portion. The rear portion of the fuselage 4 carries a pairs of wings 5.

A central propulsion unit 7 is arranged in the rear portion of the fuselage 4. According to the embodiment shown in the drawings, a propeller propulsion unit is concerned. Nevertheless, a jet propulsion engine or another suitable propulsion system could be used as an alternative.

Furthermore, a pair of stand-type tail planes 8 is attached to the individual wings 5, each tail plane being provided with a stand-type end piece 9 in order to enable the tail sitter aircraft to be parked / to stand in a vertical position.

Each wing 5 has a forward facing leading edge 50, i.e. an edge facing in the flight direction, and a rearward facing trailing edge 55. Moreover, each wing 5 is provided with a roll- control aileron 10 tiltably attached to the trailing edge 55 of the respective wing 5 in the distal area thereof and intended for controlling the rolling motion of the aircraft in flight.

Each of the wings 5 carries a propeller propulsion unit installed in the proximal area of the respective wing, the propeller 3 of the propulsion unit being arranged in the vicinity of the trailing edge 55 of the wing. With respect to the flight direction, the propeller 3 of the propulsion unit is followed by a plurality of control tabs 21, 22, 23 having their leading edges arranged substantially parallel to the trailing edge 55 of the respective wing 5.

Advantageously, the aforesaid plurality comprises at least two control tabs 21, 22, 23, the illustrated preferred embodiment comprising three. As a matter of course, the array can comprise even more control tabs 21, 22, 23. The control tabs 21, 22, 23 are attached to the respective wing 5 by means of a holder 12.

According to the illustrated preferred embodiment, the plurality of control tabs 21, 22, 23 comprises a pair of outer tabs 21, 23 and a central tab 22 arranged therebetween, the latter having its leading edge substantially aligned with the adjacent trailing edge 55 of the wing 5 when viewed in the flight direction. According to a particularly preferred embodiment, the centrally arranged control tab 22 has an aerodynamic shape which specifically means that the tab is gradually slightly widened in its central portion facing the axis of the propeller 3, as particularly apparent in Figs. 5a and 5b. Besides that, at least the centrally arranged control tab 22 has an aerodynamic teardrop shape in a section extending from the leading edge to the respective trailing edge of that tab (i.e. in a section taken through a plane parallel to the symmetry plane of the aircraft).

All the control tabs 21, 22, 23 are pivotally mounted, the respective axes of the swinging motion being parallel with each other and advantageously substantially parallel to the trailing edge 55 of the wing 5, or substantially parallel to a plane which is perpendicular to the axis of rotation of the propeller 3.

In the present exemplary embodiment, an actuating mechanism 20 is attached to the centrally arranged control tab 22, said mechanism serving for adjusting the inclination of the latter. Each of the outer control tabs 21, 23 is interconnected with the centrally arranged control tab 22 by means of a control rod 25 so that an adjustment of the inclination of the centrally arranged control tab 22 simultaneously causes a change to the inclination of the outer control tabs 21, 23. Hence, the inclination of the outer control tabs 21, 23 can be adjusted by adjusting the inclination of the centrally arranged control tab 22. This means that all the control tabs 21, 22, 23 can be arranged, for example, arranged parallel to each other and their mutual parallelism can be maintained irrespective of any change to the inclination of the centrally arranged control tab 22 (Fig. 5a, 5b).

It is obvious that the actuating mechanism 20 can be associated with any of the control tabs 21, 22, 23. Alternatively, more than one actuating mechanism 20 can be employed in order to make it possible to adjust the inclination of the individual control tabs separately / independently. Or the motion of the control tabs 21, 22, 23 may be coupled by other means.

The actuating mechanism 20 illustrated in Figs. 5 a, 5b comprises a four-joint articulated mechanism or a lever mechanism. However, other types of actuating mechanisms can be used.

Advantageously, the axes of the swinging motion of the control tabs 21, 22, 23 are arranged along the leading edges of the latter.

The leading edges of the control tabs 21, 22, 23 are arranged in a plane extending parallel to the plane of rotation of the propeller 3 of the propulsion unit arranged on the respective wing 5, the lengths of the control tabs 21, 22, 23 in the direction of the leading edges thereof being advantageously selected in a range that causes the orthogonal projections of the leading edges of the control tabs 21, 22, 23 into the plane of rotation of the propeller 3 to approximately form the chords of the circle circumscribed by the tips of the propeller 3. In the illustrated exemplary embodiment, the length of the centrally arranged control tab 22 approximately corresponds to the diameter of the circle circumscribed by the tips of the propeller 3, whereas the outer control tabs 21, 23 are shorter and their lengths approximately correspond to the size of a chord of the circle circumscribed by the tips of the propeller 3, the cord concerned having the distance from the centre of the circle equal to the distance between the leading edge of the centrally arranged control tab 22 and the leading edges of the outer control tabs 21, 23 (Fig. 3).

When taking off, the aircraft flies upwards in a vertical position, which is the position assumed by the aircraft supported by the stand-type end pieces 9 of the tail planes 8 (Figs. 1 and 2). To take off, both the central propulsion unit 7 and the propeller propulsion units arranged on the wings 5 are switched on, the outlet airflow of the latter propulsion units being vectorized in the symmetry plane of the aircraft by means of the plurality of control tabs 21, 22, 23j_k

The roll, pitch and yaw of the aircraft assuming a vertical position, i.e. the rotational motions of the aircraft around all three axes, are controlled by the combination of altering the thrust generated by the pair of propeller propulsion units arranged on the wings 5 and independent vectorizing of the outlet air flow of said propulsion units, the respective vectorization being carried out by adjusting the inclination of the control tabs 21, 22, 23.

During the horizontal flight mode (cruising mode), the central propulsion unit 7 is employed, the latter being a propeller unit or a jet propulsion one installed in the symmetry plane of the aircraft. During the aforesaid flight mode, the propulsion units arranged on the wings 5 are disabled and their propellers 3 are concealed in a mutual alignment behind the trailing edge 55 of the wing 5 or within a slot between the latter edge and the centrally arranged control tab 22. The technical solution according to the present invention is particularly suitable for unmanned aerial vehicles but may be also useful for manned aerial vehicles, such as airplanes.

Although the illustrated embodiment relates to an aircraft having a pair of front horizontal stabilizers 6, it is obvious that the present invention is also applicable to other types of aerial vehicles.

According to the particularly preferred embodiment described above, the aircraft is provided with a central propulsion unit 7 and with a pair of propeller propulsion units arranged on the wings 5. Nevertheless, an embodiment without a central propulsion unit 7 can also be used, in which case the entire propulsive force would be provided exclusively by the propeller propulsion units located on the wings 5.

Depending on the particular type of the aircraft, a suitable material for the holder 12 and/or the control tabs 21, 22, 23 can be, for example, a sheet made of a high-strength aluminium alloy.

Although multiple exemplary embodiments are described above, it is obvious that those skilled in the art would easily appreciate further possible alternatives to those embodiments. Hence, the scope of the present invention is not limited to the above exemplary embodiments and it is rather defined by the appended claims.

Claims

1. Tail sitter aircraft, comprising a fuselage (4) and a pair of wings (5), each wing having a leading edge (50) and a trailing edge (55), characterized in that each of the wings (5) is provided with a propeller propulsion unit and a plurality of control tabs (21 , 22, 23) arranged at the trailing edge (55) side, the plurality of control tabs comprising at least two pivotally attached control tabs (21, 22, 23) for controlling the direction of the air flowing from the propeller propulsion unit, the plurality of control tabs (21, 22, 23) being interconnected with a an actuating mechanism (20) for controlling the swinging of at least one of the control tabs (21, 22, 23).

2. Tail sitter aircraft according to claim 1, characterized in that the plurality of control tabs (21, 22, 23) comprises a means, preferably a control rod (25), for interconnecting the control tabs (21, 22, 23) and thereby synchronizing the swinging motion of the control tabs.

3. Tail sitter aircraft according to claim 1 or 2, characterized in that the axes of the swinging motion of the control tabs (21, 22, 23) are parallel to the trailing edge (55) of the respective wing (5) and or with the plane of rotation of the propeller of the propulsion unit.

4. Tail sitter aircraft according to any of the preceding claims, characterized in that each plurality of control tabs (21, 22, 23) comprises a pair of outer control tabs (21, 23) and one central control tab (22) arranged therebetween, the leading edge of the latter being aligned with the trailing edge (55) of the respective wing (5).

5. Tail sitter aircraft according to any of the preceding claims, characterized in that at least one of the control tabs (21, 22, 23) of each plurality has an aerodynamic teardrop shape in a section extending from the leading edge to the respective trailing edge of that tab.

6. Tail sitter aircraft according to any of the preceding claims, characterized in that it is further provided with a central propulsion unit (7) arranged in the symmetry plane of the aircraft.

7. Tail sitter aircraft according to any of the preceding claims, characterized in that the propeller propulsion unit and the plurality of control tabs (21, 22, 23) are arranged in the proximal area of the respective wing (5), whereas the trailing edge of the distal area of the wing (5) is provided with a pivotally attached roll-control aileron (10) for controlling the rolling motion of the aircraft in flight.

8. Tail sitter aircraft according to any of the preceding claims, characterized in that the control tab (21, 22, 23), which is arranged closest to the rotation axis of the propeller (3) of the propulsion unit, has a length measured in a direction parallel to the trailing edge (55) of the wing (5), the length ranging from 80 to 120 % of the diameter of the propeller (3).

9. Tail sitter aircraft according to any of the preceding claims, characterized in that the propeller (3) of the propeller unit is arranged on the respective wing (5) in a manner enabling the propeller to be aligned with the trailing edge of the wing (5) and/or concealed within a slot delimited by the trailing edge of the wing (5) and the plurality of control tabs (21, 22, 23), when the propeller is disabled.