A light-duty multipurpose aeroplane has a fuselage having a cabin at its center, a tail portion with a pusher propeller in a ring and a front portion with an all-swiveling horizontal "canard" type empennage. The wings of the aeroplane are articulated with low-mounted and high-mounted wing segments with opposite sweeps. The tips of the wing segments are connected with arrow-shaped pylons provided with heading control rudders.

FIELD OF THE INVENTION 
The invention relates to aircraft engineering and, in particular, to the 
design and aerodynamic configuration of the light-duty multipurpose 
aeroplanes. 
DESCRIPTION OF THE INVENTION 
For light-duty small aeroplanes flying at low speeds their aerodynamic 
diagrams or aerodynamic configurations are particularly important, because 
they define to a large extent the flying quality. 
The traditional monoplane type diagrams are being replaced at the present 
by ever more complicated diagrams with the intent to improve the technical 
characteristics, the importance of which is dictated by the consumer 
market. In this connection, flying qualities and service properties which 
are not crucial to aerodynamic configuration become important. This group 
of new qualities includes convenience of handling, handling-failure 
safety, redundancy of control surfaces, structural-failure safety, 
variable stability, etc. At the same time, advances in aerodynamics and 
improvement of calculation methods offer more freedom to solutions; to 
deviate earlier was hazardous because the consequences were then unknown. 
Therefore, there has been in the last few years a sharp increase in the 
quantity of original diagrams and configuration solutions, especially in 
the field of light-duty aircraft. 
Similar to the proposed technical solution are: 
aeroplanes with a pusher propeller disposed within a ring, such as the 
"Fentreiher" of the "Rhine-Flugzeugbau" Firm (FRG) and the "Optica" of the 
"Edgley" Firm (Great Britain); 
aeroplanes with an articulated wing, which have been developed on the basis 
of a biplane diagram and are being tested intensively at the present time 
in the wind tunnels of NASA (USA) for large-size commercial aeroplanes 
(FLIGHT INTERNATIONAL 4, 1987, p. 16). 
The technical solution most similar to the present invention is the design 
realized only in a single aeroplane created by amateur craftsmanship in 
Australia by Charles Ligeti, a Czech immigrant, i.e. the LGT Stratos 
(FLIGHT INTERNATIONAL, 6, 1986, p. 46). This is a single-seat powered 
glider aeroplane having an articulated wing of low-mounted and 
high-mounted swept-back wing segments connected at their tips by pylons. 
In the tail portion of the fuselage there is a pusher propeller mounted 
inside a ring. 
The disadvantages of the aeroplane configuration last described above 
include the problematic character of operating characteristics if this 
aeroplane is re-designed for carrying more than three passengers over 
routes as long as 1500 km with earthen runways. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to create a light-duty 
multipurpose aeroplane having high carrying properties and enhanced 
stability. 
The object is met in an aeroplane having articulated wings each consisting 
of low-mounted and high-mounted wing segments connected at their tips by 
pylons as well as a pusher propeller mounted in a ring at the tail portion 
of fuselage. The upper and lower wings are spaced apart along the 
aeroplane's longitudinal axis and have mutually opposite sweeps, thus 
forming a rhombus shape in the plan view, and in that pitch control means 
and heading control means are provided. 
According to the preferred embodiment, the lower wing segments may have a 
back sweep and the upper wing segments, a forward sweep. The opposite 
sweeps of the low-mounted and high-mounted wing segments permit optimum 
advantages of air flow around the wings, i.e. circulation, thus ensuring a 
more uniform lift distribution over the wing span. 
The upper wing segments can be installed at the top of the pusher propeller 
ring. The embodiment with the high-mounted swept-forward wing segment 
located at the top of the pusher propeller ring makes it possible to 
isolate that wing from burbling if the flow separates from the low-mounted 
wing at large angles of incidence, due to drawing in of the separated air 
flow by the propeller. 
Lower swept-forward wing segments can be installed at the bottom of the 
pusher propeller. 
The root and tip sections of the wing can be spaced apart heightwise, e.g. 
in a vertical direction, to different degrees so that symmetrical 
trapezoids are formed. 
It is advisable to ensure that the vertical spacing at the root section of 
the wing is at least as great as one length of its root chord, whereas the 
spacing at the root section along the axis is made in conformity with the 
geometrical dimensions of the fuselage. 
The connection of the wing tips with pylons makes it possible to create a 
rigid load-bearing structure--a wing "box"--forming two symmetrical 
trapezoids in the front view. Such a structure reduces deformation in the 
root sections of the wings and improves fatigue strength, and also, in 
combination with the general configuration, improves both general and 
dynamic strength. 
By using various transverse V's for the wings, one can ensure the largest 
vertical spacing between the root sections of the two wing segments on 
each side of the fuselage and provide favorable conditions, by means of an 
arrow-shaped pylon connecting the tips of the wings, for creating a wing 
box that is rigid from the viewpoint of bearing its load. With this, 
deformations become substantially smaller in the root sections of the 
wings so that the fatigue strength of the aeroplane is enhanced. This is 
important when composite materials based on epoxy resin are used for the 
wings as these materials are characterized by low bending strength. 
In the final analysis, the design of an articulated wing in combination 
with the general configuration makes it possible to reduce the weight of 
the aeroplane, to increase the carrying load and to improve both general 
and dynamic strength. 
The claimed relationship between the spacings of the chords of the tip and 
root sections of the wings both heightwise and lengthwise was obtained 
from the results of wind-tunnel tests. The calculation of the chord 
spacing makes it possible to obtain a flow under super-critical conditions 
that avoids snapping the aeroplane into a spin. 
According to one of the embodiments, the pitch control means is implemented 
in the form of a front-set horizontal "canard" type empennage. A front-set 
horizontal "canard" type empennage ensures a substantial improvement in 
the carrying properties of the aeroplane and improves its stability. 
The front-set horizontal empennage and high-mounted and low-mounted wings 
are preferably spaced along the longitudinal and heightwise axes of the 
fuselage relative to one another. 
An all-swiveling horizontal "canard" type empennage substantially improves 
aeroplane controllability in the case of a large spread of the 
center-of-gravity locations, since this unit, depending upon its angle of 
incidence, moves the center of pressure forward, thus adjusting the degree 
of aeroplane stability. 
Pitch control is attained with elevators disposed on wings and by the use 
of the front-set horizontal empennage. The simultaneous utilization of 
these means makes it possible to control the lift directly. Elevators 
disposed on the high-mounted wing enable the wing to be used as an 
additional horizontal empennage (stabilizer), thus improving efficiency of 
control of the aeroplane under normal conditions. 
Heading control is attained with the help of rudders on the wing-tip pylons 
and on a tail fin. The simultaneous utilization of these means makes it 
possible to control the lateral force directly. 
According to another embodiment, an additional rudder is provided in the 
propeller slipstream, this rudder being made as a fin extension. A similar 
slip-stream rudder can also be provided in the horizontal plane for pitch 
control at low speeds when other means are less efficient.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As shown in FIGS. 1 to 3, a light-duty multipurpose aeroplane comprises a 
fuselage 1 having a cabin 2 arranged at its caner. At the tail portion of 
the fuselage, a pusher propeller is mounted in a ring 3. The front portion 
of the fuselage is provided with an all-swiveling horizontal "canard" type 
empennage 4. 
The wings of the aeroplane are articulated. Each consists of low 
fuselage-mounted swept-back wing segments 5 and high-mounted wing segments 
6 that sweep forward from a the top of the ring 3 and are provided with 
elevators 7 (FIG. 3). 
The tips of the high and low wing segments are respectively connected with 
arrow-shaped pylons 8 provided with heading control rudders 9. 
A front undercarriage and a rear undercarriage 11 are attached to the 
fuselage. 
In the embodiment of the aeroplane design according to FIG. 4, there is a 
fin 12 mounted at the top of the ring 3 enclosing the pusher propeller. 
The fin is provided with a heading control rudder 13. Another turning 
rudder 14 is mounted in the propeller slipstream. 
In this embodiment, the arrow-shaped pylons 8 may carry further heading 
control rudders 9, as shown, but do not have to. 
FIGS. 7 to 9 show an embodiment of the aeroplane having an articulated wing 
with the swept-back wing segments 5 being high-mounted and the 
swept-forward wing segments 6 being low-mounted, attached to the bottom of 
the ring 3 and provided with elevators 7. 
An all-swiveling fin 12 is installed at the top of the fuselage for heading 
control instead of the rudder 13 of FIG. 4. 
These aeroplanes have a number of material advantages, namely: 
improvement in carrying properties; 
improvement in stability and controllability; 
improvement in fatigue strength; 
direct control of the lift and lateral forces; and 
safety and convenience of aeroplane-handling. 
The designs of these light-duty multipurpose aeroplanes have been 
implemented in the development of the "SAVIAT E-1" aeroplane made of 
composite materials based on glass fibers. 
When used for individual purposes, the aeroplane is designed for operation 
by an inexperienced pilot who has taken only a course of initial training. 
The design therefore takes into consideration that the aeroplane should be 
able to land on a motor road, a street and other areas of terrain not 
designed for the landing of an aeroplane. On this basis, the wing span was 
selected to be equal to 7 m, the length of the aeroplane, to about 6 m, 
and the diameter of the fuselage, to about 1.5 m. Since a pusher propeller 
is installed, the engine is protected against being hit by various foreign 
objects. 
The data of wind-tunnel testing indicate that the object of the present 
invention--i.e., optimization of aerodynamic properties of the aeroplane 
as a whole--has been attained, thus ensuring safe and easy 
aeroplane-handling. 
Some elements of the disclosed aerodynamic configuration of the airframe 
can be used in the designs of ground-effect machines, hovercrafts, 
hydroplaning vessels and hydrofoil crafts, as well as in class racing 
cars.