FR2762290A1 - LIGHT AIRCRAFT HAVING A SOLAR DRIVE DEVICE - Google Patents

Abstract

In this light aircraft comprising lifting surfaces (10, 11) arranged on parts (12, 13), connected to a tail unit (15), of a double fuselage (12, 13) of the aircraft carrying propellers (31 at 34), the motors are powered by solar cells located on additional surfaces (21, 22, 25, 26) of the double fuselage, the general neutral point of which is located at the aircraft's center of gravity and which can be oriented with respect to the sun. Application in particular to small remote-controlled observation planes powered by solar cells.

Description

LIGHT AIRCRAFT HAVING A SOLAR DRIVE DEVICE

  The invention relates to a light aircraft powered by a solar drive device, in particular a small aircraft.

  solar powered observation remote control, including

  both solar cells used to generate energy and

  at least one propeller driven by an electric motor.

  Such aircraft are known for example from documents DE-OS 26 16,000, US 4,697,761 or DE

296 16 989 U1.

  Small remote-controlled observation planes are light planes powered by solar energy and used to fly at heights exceeding 000 m to make observations. In particular, for example, small remote-controlled planes powered by

  solar energy for observing time, sur-

  face of the ground, airspace control, for tele-

  communications or defense technology. In addition, solar drive devices are used by

  example also for motor gliders.

Planes with a device

  solar drive units have on their surfaces

  aunts, photovoltaic solar cells used to pro-

  draw an electric current which is used to

  propeller drive using electric motors.

  Since solar powered planes have no

  no need to take fuel, they can be refueled

  with a light construction; with such aircraft, long flight times can be obtained. To the extent of

  such aircraft are equipped with an additional energy accumulator

  excess energy can be stored during

  during the day and be available at night so that

  night flights are also possible. We can therefore

  quent obtain flight durations of several months.

  The photovoltaic solar cells are arranged horizontally on the upper side of the aircraft. This is why the energy efficiency is low in the case of the low height of the sun so that the flight times of several months in the northern hemisphere in winter are not

  possible only in a limited way.

  To be able to obtain long flight times also in winter and to be able to accommodate substantial payloads on the plane, it is therefore necessary to increase

  the wing surfaces to be able to predict a sufficient number

  using solar cells. An increase in the area of the wings, however, has the drawback that the speed of movement is reduced. To be able to bring a small remote-controlled device to be stationary in a specific area, however, its speed must be

  higher than the wind speeds that are present.

  Since the upper face of the wings or bearing surfaces is curved and the wings must be elastic, the installation of solar cells on the upper face of the wings is very difficult since the solar cells are extremely sensitive to pressure. So that the aerodynamics of the wings are as little influenced as possible, thanks to the use of

  expansion joints between the solar cells and the plate

  birth of solar cells, solar cells must be placed on the wings by means of the implementation

  extremely complicated installation procedures.

  Due to the installation of the solar cells, the wings must be made with a stable construction. This increases the weight of the wings so that an optimization of the weight and the surface of the wings is not

  possible. Particularly in the case of solar cells

  laid obliquely on the wings, it can appear additional tearing edges, which cause undesirable vortices. On the other hand, due to

  complicated installation of solar cells, a replacement

  Damaged solar cells are only possible

  through the implementation of a high expense.

  According to DE 29 51 699 Ai it is known to climb, respectively on the left wing and on the right wing of a

  metal glider in the form of ribbons

  relatively thin, on which are placed semiconductor solar cells. Solar bands of this type perform a very intense beat during a flight and

  thereby lead to a very large aerodynamic drag

  mique. In addition, such stacks formed of thin films have a very low efficiency so that solar strips having a particularly large surface would be necessary, which would further increase the aerodynamic drag. In addition, the solar bands are hooked only by their front end to the wings, which means that they must produce aerodynamic lift themselves for their weight.

clean.

  This is why the invention aims to create a light aircraft comprising a solar drive device, in which the solar cells are arranged so that an energy efficiency can be obtained.

  high for simultaneously low air resistance.

  This problem is solved in accordance with the invention thanks to the fact that the solar cells are arranged on

  additional surfaces, provided outside of the

  bearing faces of the airplane and whose general neutral point is located at the center of gravity of the airplane and which can

  be oriented with respect to solar radiation.

  According to the invention the solar cells are arranged on additional surfaces, which are provided on the outside of the wings and whose overall neutral point or barycenter is preferably located at the center of gravity of the vehicle. Consequently, the structure of the wings can be optimized with regard to their shape and their weight. In particular, the curved surface of the wings is not

  not affected by the presence of solar cells.

  In addition, for the transport of high payloads or for flights with a low incidence of the sun, it is not necessary to increase the surface of the wings, so that higher flight speeds can be obtained, which facilitates positioning of small remote-controlled observation planes. On the other hand, the weight of solar cells does not have to be supported by the wings, so that the latter can be produced with a

optimized lightweight construction.

  The fact that the general neutral point of surfaces

  is preferably located in the center of gra-

  The great advantage of the aircraft is that, when changes in the angle of attack occur, such as in the case of gusts of wind, the additional surfaces do not show any force producing free couples around the center of gravity. Consequently, whatever the position of the additional surfaces, their influence on the flight stability and the control capacity of the aircraft is very weak. The additional surfaces are arranged by

  example directly on the fuselage. Additional surfaces

  may also be provided on the airplane so as to form the fuselage or parts of the airplane fuselage. In addition, the additional surfaces can be oriented according to the invention according to the

  solar radiation. Therefore the tilt of the over-

  additional faces relative to the sun's rays can be oriented respectively so that the surface

  solar cells is permanently arranged perpendicular to the

  the sun's rays. Optimal energy efficiency is possible due to the capacity

orientation of solar cells.

  This is why it is possible to use the light aircraft according to the invention comprising a solar drive device, even in the case of a low incidence of solar radiation, during long flight times so that flights long lasting during the winter months are

  also possible. Even during the summer months, the

  energy is optimized during morning periods

  and evening so the plane can park at a high

  higher or that the energy required for the night flight can be supplied by a lower number of solar cells. This again has the advantage of

  what the weight of the plane is reduced.

  Preferably, the additional surfaces can

  wind, for alignment, rotate respectively around at least one axis. For example, rectangular surfaces can be provided as additional surfaces, the axis of which

  longitudinal is parallel to the longitudinal axis of the airplane.

  To reduce the resistance of the additional surfaces, the longitudinal axis of the airplane must pass at the reference point of the light airplane, parallel to the flight path. Such additional surfaces can be

  fixed by retainers arranged parallel-

  lying on the fuselage. In addition the fuselage itself can be arranged in the form of a tubular construction, which

  is used for fixing additional surfaces.

  For alignment, the additional surfaces can pivot around their longitudinal axes. On a

  such a retaining device can also be provided for

  several additional rectangular areas, including the axis

  longitudinal is oriented perpendicular to the long axis

  tudinal of the plane. Such additional surfaces may

  wind preferably rotate as well around a long axis

  gitudinal than around an axis perpendicular to the longi-

  tudinal of the plane. Thanks to this second axis of rotation, the additional surfaces can be adjusted independently of the flight state of the aircraft so that no force appears at these surfaces. The flight characteristics of the light aircraft are therefore independent

  the size, position and orientation of the sur-

  additional faces. Retaining devices or sup-

  port for additional areas can be equal

  ment provided on the wings of the aircraft.

  Preferably the adjustment of the additional surfaces

  This is done using self-locking transmissions, driven by electric motors. Therefore, when adjusting additional surfaces for low current consumption, only small forces are used. In addition it is possible to have auxiliary rudders for orientation, on the

  additional surfaces. The orientation of the sup-

  can be performed by calculating the position of the sun relative to the plane. For this purpose, the precise position and attitude of the aircraft, the time of day

  as well as the date are required.

  In a preferred embodiment of the additional surfaces, the latter are arranged so that they can be reduced. As a result, the aerodynamic drag caused by the additional surfaces can be greatly reduced, for example in the case of night flights. To reduce the extent of the additional surfaces, these consist for example of several partial surfaces, which are connected between

  hinged so that the surfaces

  can be folded over each other.

  According to another embodiment, the additional surfaces are formed by several

  partial surfaces that can slide telescopically

  spades. In addition it is possible to provide, as additional -7 surfaces, flexible solar sheets,

  which can be rolled up to reduce surfaces.

  To increase the energy gain, we can also

  Put solar cells, which act on two sides, on a transparent panel structure. Therefore indirect radiation or radiation reflected by the earth can be used and this in the case of a weight

almost unchanged.

  In the case of the use of an airplane for observation purposes, the position and attitude of the airplane are permanently determined - for example by a so-called "GPS" system - so that these data can be

  used to calculate the enslavement of the sup-

  additional to the position of the sun. Otherwise, for the enslavement of the additional surfaces we can

  also provide light sensors on these

site.

  To increase the energy gain, you can pre-

  see, in addition to the additional surfaces, also solar cells on the wings and / or the empennage and / or the

  fuselage. Since these solar cells serve uni-

  only to obtain an additional energy gain, they can be placed, for example, on the support surfaces so that the configuration of the wing profile does not

  is not influenced or is only influenced

badly.

  Other features and advantages of the pre-

  sente invention will emerge from the description given below

  after reference to the accompanying drawings, on the-

  which: - Figure 1 shows a schematic perspective street of a preferred embodiment of an airplane

  lightweight according to the invention comprising a driving device

  solar energy; - Figures 2a to 2e show schematic plan views of different possibilities of arrangement of additional surfaces; - Figure 3a shows a schematic cross-sectional view of an additional surface; - Figures 3b to 3e show cross-sectional views of different embodiments of folded additional surfaces;

  - Figure 4a shows a cross-sectional view

  versale of an additional telescopic surface; and

  - Figure 4b shows the additional surface

  shut up shown in Figure 4a, in the retracted state.

  The embodiment, shown in Figure 1, of a light aircraft comprising a solar drive device has bearing surfaces or wings 10, 11. The wings 10, 11 are connected to a double fuselage, a first tubular part 12 of the fuselage

  being connected to wing 10 and a second part 13 of the fuser-

  the beam being connected to wing 11. The two tubular parts

  12, 13 of the fuselage extend parallel to the long axis

  tudinal 35 of the aircraft and are interconnected by means of a tail fin 15 for the stabilization of the aircraft. Respective rudders 16 and 17 are provided on the ends, which are aft in the

  direction of flight, tubular parts 12, 13 of the fuselage

age.

  In the area of parts 12, 13 of the fuselage between

  the wings 10, 11 and the empennage of depth 15, sur-

  additional faces 21, 22 are connected to parts 12 and 13 of the fuselage. The additional surfaces 21, 22 are equipped with solar cells not shown in a way

  detailed. The additional rectangular-shaped surfaces

  area 21, 22 can pivot around their longitu-

  23 or 24 channels parallel to parts 12, 13 of the fuselage.

  Similarly, rectangular surfaces 25, 26 are arranged on the areas of the parts 12, 13 of the fuselage, which project forward in the direction of flight beyond the bearing surfaces or wings 10, 11. Like the additional surfaces 21 , 22, additional areas 25, 26

  can also pivot around their longitudinal axes

  nals 27, 28, which extend parallel to the parts 12,

  13 of the fuselage. Therefore, the additional surfaces

  shields 21, 22, 25, 26 can be oriented towards the sun by pivoting around their longitudinal axes 23, 24,

26, 28.

  The energy, which is produced by the solar cells placed on the additional surfaces 21, 22,, 26, is used primarily to drive propellers 31,

  32, 33 and 34 as well as to rotate the additional surfaces

  electric motors not shown.

  The propellers 31, 32, 33, 34 are driven respectively by electric motors also not shown. The propellers 32, 34 are provided on the front end, in the flight direction, of the parts 12, 13 of the fuselage and are therefore arranged directly in front of the additional surfaces 25, 26. The other two propellers 32, 33 are

arranged on the wings 10 and 11.

  In addition, the aircraft shown in Figure 1 pos-

  an energy accumulator not shown in detail. The energy accumulator is charged by the excess energy which is produced by the solar cells.

  during the day. The solar cells provided on the over-

  additional faces are arranged so that

  during the day at least an excess amount of energy is produced to such an extent that sufficient energy is

  available for the next night flight.

  As an energy accumulator, an electrolyser is used, for example, in which the water is dissociated

  in H2 and 02. During the night flight, gases H2 and 02 accumulate

  mules in a fuel cell are converted into

  electric for driving propellers 31, 32, 33, 34.

  These gases can for example be stored in the longitudinal members of the wings arranged in a tubular shape or else in the

fuselages 12, 13.

  Since the parts 12, 13 of the fuselage are arranged symmetrically and parallel to the longitudinal axis 35 of the aircraft and that the additional surfaces 21, 22, 25, 26 are arranged on the tubular parts 12, 13 of the fuselage , the general neutral point is located at the center of gravity of the airplane, in the case of a position and

  correct size of additional areas.

  The calculation of the general neutral point can be exe

  cut on the basis of equations indicated below, which relate to the calculation of a general neutral point of the additional surfaces 21, 22, 25, 26 represented in the figure

  1, the parameter characterized by the index 1 concerning res-

  pectively the additional areas before 25, 26, tan-

  say that the parameter characterized by index 2 concerns

  the rear additional surfaces 21, 22.

  In the following table, we give the indi-

  cations of the different parameters and their uni-

  your. Parameter Meaning Unit

  CA Ascension thrust coefficient-

  nelle, entire aircraft m2 S Reference surface m2 V Speed m / s bpt Plate width m lpt Plate length mq Dynamic pressure kg / (m.s2) XN Position of neutral point m A Elongation, Apt = bpt / 1pt a Angle of attack radians aW Downwind angle radians ges Total value Pt Plate

  The general neutral point xN, PtgeS can be cal-

  culated in accordance with the following relation (1): cA. XNPI + CA "r q S. 1 _ 'w) X. * XN.P4es = + (I I

CAa.h + CAa ..- q _m. 1-

  As a first approximation, the dynamic pressure qPtl of the additional front surfaces 25, 26 can be balanced with the dynamic pressure qPt2 of the rear additional surfaces 21, 22. Furthermore, as a first approximation, the variation of the downward wind angle with respect to the angle of attack. Consequently, the relation (1) of the general neutral point is simplified, which leads to the relation (2): Ca.haI ÀXN.! + CAa.2 À S XN.a XN'Pt = St (2) 3CAa. Pti + CAa (Pt2 Sp SP 'The coefficient of ascent CAapt which is contained in the relation (2) and depends on the angle of attack, of each additional surface (21,22,25,26) can be calculated in accordance to relation (3): C <Aa.Pt = (An The distance XN Pt between the neutral point of

  flat plate and the front edge of the plate can be obtained

  roughly naked in accordance with relation (4):

XN.P I * A (4)

1.5 + 2.25 +16 * A

  The arrangement, which is shown in FIG. 1, of additional surfaces 21, 22, 25, 26 has the advantage that the weight of the surfaces can be kept at a relatively low value since the lever arms and by therefore the forces which

  appear, are weak. In addition, aerodyna-

  mique of additional surfaces is weak and the influence of additional surfaces 25, 26 on

  the flow along the wings is also weak.

  In addition, the additional surface restraint hardly causes the existence of additional weight since the restraining devices

  are used as parts 12, 13 of the fuselage.

  On the other hand, you can get a good swivel capacity -

  additional surfaces 21, 22, 25, 26 since the corresponding devices for pivoting the additional surfaces can be arranged in the

parts 12, 13 of the fuselage.

  In Figures 2a to 2d there are shown

  different embodiments for mounting sur-

  additional faces intended to receive solar cells, on an airplane. The aircraft shown in Figure 2a

  essentially corresponds to the structure of the aircraft shown

  felt in Figure 1. The two additional surfaces 25 and 26 are shown on the parts 12, 13 of the fuselage, in front of the wings 10, 11 in the flight direction. The two additional surfaces 21 and 22 are shown behind the wings 10 and 11 in the flight direction, on the parts 12 and 13 of the fuselage. In addition, rudder rudders 16 and 17 as well as the rudder 15 are shown in a plan view. Unlike Figure 1, in the schematic representation of an airplane on

  FIG. 2a, only two propellers 31 and 34 are shown

tees.

  The airplane shown in FIG. 2b corresponds, from the point of view of the principle, to the arrangement of the airplane

  shown in Figure 1. On parts 12, 13 of the fuser-

  lage are provided, and this in front of the wings 10, 11 in the

  direction of flight, not additional areas

  pectives in one piece 25, 26, but respectively two additional surfaces 51, that is to say in total four additional surfaces. Behind the wings 10, 11 in the flight direction are provided, on the parts 12, 13 of the

  fuselage, not respectively the additional surfaces

  all in one piece 21, 22, but respectively three

  additional areas 52, i.e. a total of six areas

  additional faces. Their longitudinal axes extend

  perpendicular to the parts 12, 13 of the fuselage. Because

  sound of the shallow depth of the additional surfaces, the latter can also be achieved by being

  profiled, in order to reduce the resistance of the surfaces

additional.

  The additional surfaces 51, 52 are available

  respectively symmetrically relative to the parts

  12, 13 of the fuselage, so that their median axes coincide

  tooth respectively with the longitudinal axes, which are parallel to the flight direction, of parts 12 and 13 of the

  fuselage. In this embodiment, all the sur-

  additional faces 51 and 52 can rotate as well

  around their median axes than around their long axes

  tudinaux. Therefore, an orientation of the sup-

  additional along the instantaneous flight path is possible regardless of the flight direction. As a result, the additional surfaces 51 and 52 produce almost no induced resistance in all the flight positions. The orientation of the additional surfaces 51, 52 around their longitudinal axis can be effected by means of the air flow. For this purpose the axis of rotation of these additional surfaces must be freely movable and is located in front of the respective neutral point of the additional surface. In addition, the center of gravity of this additional surface should be located respectively

on its axis of rotation.

  The airplane shown in FIG. 2c comprises bearing surfaces or wings 10, 11, which are fixed to a fuselage 40. As regards the fuselage 40, it is

  an individual fuselage, the longitudinal axis of which

  lays on the longitudinal axis 35 of the airplane. The rudder 41 is disposed on the end of the fuselage 40, which is located aft in the direction of flight, while a propeller 42 is provided on the front end, in the direction of flight, of the fuselage 40. On the wing 10 are arranged, by

  through retainers 43 indicated only

  Lement schematically, in front of the wing 10 in the flight direction, additional flat surfaces of rectangular shape 44, which can pivot about their axis lor.ngitudir.al which is parallel to the flight direction. Behind the wing 10 when looking in the direction of flight, other additional surfaces 46 are mounted, by means of retaining devices 45, at the height of the additional surfaces 44, so that the longitudinal axes, not specially designated additional surfaces, also flat and rectangular

  46 coincide with the longitudinal axes of the upper surfaces

additional 44.

  On wing 11 are arranged, by means of provision

  retaining devices 47, additional surfaces 48, which correspond to additional surfaces 44 and can also pivot around an unnamed longitudinal axis

  in a particular way. Furthermore on wing 11 are available

  by means of retaining devices 49, surfaces

  additional 50, which correspond to the additional surfaces

  46 and can also pivot around an axis

  longitudinal not specifically designated.

  The embodiment shown in Figure 2c has the advantage that the mass of

  additional areas 44, 46, 48, 50 is evenly distributed

  formally on the wingspan of the aircraft and therefore

  unloads the structure of the wing. Furthermore the form of rea-

  reading shown in Figure 2c can also be

  used in the case of so-called "flying wings" aircraft.

  In Figure 2d, there is shown another embodiment for mounting additional surfaces on an aircraft. Several additional surfaces 55 and 56 are arranged between the two parts 12, 13 of the fuselage, upstream and behind the wings 10, 11 in the flight direction. The additional surfaces 55, 56 also have a planar and rectangular shape. The longitudinal axes of the additional surfaces 55, 56 are parallel to the longitudinal axis 35 of the aircraft and can pivot around their longitudinal axes. The arrangement, shown in FIG. 2d, of the additional surfaces 55, 56 creates an urn

  large surface, which can be fitted with solar cells.

* To reduce the resistance, the additional surfaces, 56 can be easily folded transversely by

  relative to the longitudinal axis of the vehicle.

  In the case of the embodiment shown

  shown in FIG. 2e, it is for example a conventional aircraft, to which a sheet forming a solar cell or "solar sheet" with a thin layer 60 is fixed by means of a towing cable 61. For the alignment of the solar sheet 60, it is possible to provide, on a retaining device 62 of the

  solar sheet, auxiliary rudders not shown

  your. The embodiment of FIG. 2e has the advantage that the aerodynamics of the aircraft are not influenced by the additional surface in the form of the solar sheet 60, and the solar sheet 60 has an extremely high weight. low. In addition, the winding and unwinding of the solar sheet 60 can be

  executed in a simple way. Corresponding solar sheets

  with the usual technology have a relatively

tively weak.

  In Figure 3a, there is shown, in cross section, a rigid additional surface 29, which is equipped with solar cells and which corresponds for example to

  embodiments of FIGS. 1 and 2a of the surfaces

  21, 22, 25 or 26. The additional surface 29 is fixed to a tubular part 12 ′ of the fuselage, at

  using a U-shaped retainer 65. The device

  retaining positive 65 is therefore connected to the part

  12 'of the fuselage so that the additional surface

  shutter 29 can pivot about its longitudinal axis 23 ', at

  using pivoting devices not shown.

  Referring to Figures 3b to 3e, there are shown possible embodiments allowing the folding of an additional surface 291. For this purpose the additional surface 291 is constituted, as shown in Figure 3b, by several partial surfaces 66, 67 , 68, which are interconnected by means of joints 69, 70. Consequently, it is possible to

  reduce the aerodynamic drag of the additional surface

  keep quiet 291, for example during a night flight, by the fact that the additional surface 29 is folded back, from the position shown in FIG. 3, at the articulated connections 69, 70, so that the three partial surfaces 66 , 67, 68 are arranged around the part 12 of the fuselage, forming a triangle in cross section

  isosceles or even an equilateral triangle.

  In FIG. 3c, parts of the same extent 66 ', 67' and 68 'of an additional surface 292 are connected together in an articulated manner so that the part or partial surface 66' can be folded over the

  lower partial surface 67 ', which is connected to the dispo-

  retaining sitive 65 U-shaped, and the part or partial surface 68 'is applied to the part or partial surface 66' In the embodiment shown in Figure 3d, the additional surface 293 is subdivided into seven parts or partial surfaces, a partial surface 71 having the width of the U-shaped retainer 65, and the areas, which protrude beyond this width in both directions, of the partial surface 293 being subdivided into three, it that is to say that they are subdivided into three respectively identical partial surfaces 72. The respective three partial surfaces 72 of the partial surface 293 subdivided into three are connected to each other respectively in an articulated manner so that they can be folded on themselves by applying to each other on three layers. In the folded state, the three respective partial surfaces 72 are applied laterally against the retaining device 65. In another embodiment shown in FIG. 3e, two partial surfaces 73 can be

  folded over the partial surface 74 which is connected to the device

  positive restraint 65. Unlike the form of realization

  tion shown in Figure 3c - the partial surfaces 73 do not overlap. Thus the embodiment of the partial surfaces 73 linked together by articulation

  is simpler but the remaining extent of the upper surface

294 is larger.

  Figures 4a and 4b show a pos-

  sibility of reduction of an additional surface 295. The additional surfaces 295 are formed by three partial surfaces 75, 76, 77, in which case the middle surface 76 is

  connected to the retainer 65. The other two over-

  partial faces 75, 77 can be telescopically fitted into the partial surface 76 by the fact that

  under the effect of the telescopic insertion of the surfaces

  65, 76 and their introduction into the surface par-

  medial tial 66, the area of the additional surface 291 can be reduced, as shown in FIG. 4b.

Claims (17)

  1. Light aircraft with a training device   solar powered, equipped with solar cells for power supply   tion in energy and at least one propeller (31 to 34) driving   born by an electric motor, characterized in that the   solar cells are arranged on additional surfaces   shutters (21,22,25,26; 29; 291 to 295; 44,46,48,50; 51,52; 55, 56), provided outside the bearing surfaces (10,11) of the airplane and whose general neutral point is located at the center of gravity of the airplane and which can be oriented compared to solar radiation.   2. Light aircraft according to claim 1, character-   rised in that the additional surfaces (21,22,25,26; 29; 291 to 295; 44,46,48,50; 51,52; 55,56) can, for their orientation, pivot respectively around at minus one axis (23,24,27,28).   3. Light aircraft according to claim 2, character-   rised in that the additional surfaces (21,22,25,26; 29; 291 to 295; 44,46,48,50; 51,52; 55,56) can pivot around axes parallel and / or perpendicular to the axis longitudinal (35) of the aircraft.   4. Light aircraft according to claim 3, character-   rised in that the additional surfaces, which can pivot around a second axis, are oriented during the   flight, by the air flow which then appears.   5. Light aircraft according to claims 1 to 3   taken as a whole, characterized in that for orientation, light-sensitive sensors are provided on the additional surfaces (21,22,25,26; 29; 291 at 295; 44.46.48.50; 51.52; 55.56).   6. Light aircraft according to claims 1 to 3,   characterized in that additional surface adjustment   res (21,22,25,26; 29; 291 to 295; 44,46,48,50; 51,52; 55,56)   is carried out using a self-locking transmission.   7. Light aircraft according to any one of the res-   dications 1 to 6, characterized in that the additional surfaces   mental (21,22,25,26; 29; 291 to 295; 44,46,48,50; 51,52; 55, 56) are flat.   8. Light aircraft according to one of claims   previous, characterized in that the additional areas (21,22, 25,26; 29; 291 to 295; 44,46,48,50; 51,52; 55,56)   can be steered using auxiliary rudders.   9. Light aircraft according to any one of the res-   dications 1 to 8, characterized in that the surface area   additional (291 to 295) can be reduced.   10. Light aircraft according to claim 9, charac-   terized in that the additional surfaces (291 to 294) consist of several partial surfaces (66 to 68; 66 ′ to 68 ′; 71, 72; 73, 74) which are connected to each other in an articulated manner and can be folded for the   reduction of the area of these surfaces.   11. Light aircraft according to claim 9, charac-   terized in that the additional surfaces (295) consist of several partial surfaces (75 to 77) sliding telescopically to obtain a reduction of the surface area.   12. Light aircraft according to any one of the res-   dications 1 to 11, characterized in that solar cells, which act on two sides, are mounted on a structure shaped like a transparent panel.   13. Light aircraft according to any one of the res-   dications 1 to 12, characterized in that the surfaces above   (21,22,25,26; 29; 291 to 295; 44,46,48,50; 51,52;, 56) are retained on the fuselage of the aircraft or on   parts (12,13) of the aircraft fuselage, using retaining devices (65).   14. Light aircraft according to any one of the res-   dications 1 to 13, characterized in that retaining devices (43, 45,47,49) for the additional surfaces (44,46,48,50) are provided on the bearing surfaces (10,11) from the plane.   15. Light aircraft according to any one of the res-   dications 1 to 14, characterized in that the propellers (31,34)   are provided on the additional surfaces (25,26).   16. Light aircraft according to any one of claims 1 to 15, characterized in that additional solar cells are provided on the bearing surfaces or wings (10,11) and / or on the tail (16,17) and / or on the fuselage (12,13).   17. Light aircraft according to any one of the res-   dications 1 to 16, characterized in that data from a so-called "GPS" navigation system, which determines the position of the vehicle, can be used to calculate the enslavement of the additional surfaces relative to the position of the sun.