DE102019202354A1 - Brushless aircraft - Google Patents

Abstract

The present application relates to an aircraft (10) which is designed as a tailless aircraft (10) and has a wing (12) with a wing nose (14). According to the invention, the aircraft (10) has a flow separation edge (18) on the wing nose (14), which is designed to tear off the lift-generating edge (18) over the wing at a certain angle of attack of the wing (12) (12) to cause a running flow.

Description

TECHNICAL AREA

The present invention relates to a tailless aircraft having a wing with a wing nose.

BACKGROUND

A tailless aircraft is to be understood as meaning an aircraft which, apart from its main wing, does not have a separate horizontal stabilizer in the form of a further horizontal aerodynamic surface. A special type of tailless aircraft is the flying wing aircraft, also called "flying wing" or "flying wing".

In conventional aircraft there are normally two horizontal aerodynamic surfaces available, namely in addition to the main wing, i.e. a wing, a horizontal stabilizer. This can be arranged behind the main wing or, as in a duck plane, in front of it. The horizontal stabilizer has a great influence on the longitudinal stability of the aircraft. It not only enables the center of gravity of the airworthy aircraft to be located within relatively wide limits along the longitudinal axis, but also the flight behavior of the aircraft at high angles of attack can conventionally be easily controlled. In the present case, the angle of attack is to be understood as the angle between the flow impinging on the wing and the chord of the wing profile.

Conventional aircraft are typically aerodynamically designed in such a way that the lift-generating flow over the wing ("flow separation") breaks off first in the area of the wing root, i.e. takes place at the fuselage-surface transition in the transverse direction relatively far in the middle of the aircraft. This particularly reduces the roll moment caused by a one-sided stall. In addition, this aerodynamic design of the aircraft means that the aircraft is already showing the first signs of stall (caused by the stall in the area of the wing root), while it can still be steerable because the ailerons are still weak because the flow has not yet stalled here have to be.

A licensing requirement for an aircraft is usually that it must be able to be brought back into an airworthy flight condition after a stall. This is usually achieved by a suitable center of gravity relative to the aerodynamic pressure point in this flow state. In short, the aircraft tilts forward or over the side in such a way that the lift-generating flow quickly rests sufficiently far over the wing again.

In the case of tailless aircraft, there are systemic difficulties here that, unlike conventional aircraft, have to be overcome.

In order to compensate for the missing horizontal stabilizer, one approach for a tailless aircraft is to provide a relatively strong positive sweep, in particular of the leading edge of the wings. This is understood to mean a wing shape in which the wings, in particular their leading edge, are angled backwards with respect to the transverse axis of the aircraft.

A disadvantage of the swept wings, however, is that the vortex pattern is displaced outwards towards the wing tips when the flow stall compared to less strongly swept wings. In other words, the stall no longer begins at the wing root, but further out and therefore further back due to the sweep. In the case of a tailless aircraft, this can go so far that the stall begins behind the aircraft's center of gravity. This is associated with various disadvantages, some of which are serious.

Firstly, a stall behind the center of gravity means that the aircraft does not tip straight forward because the lift force breaks off behind the center of gravity while lift is still being generated in front of the center of gravity. In many cases, this effect leads to lateral tilting and spinning or a spiral fall.

Secondly, a one-sided stall in an outer area of the wing leads to a large roll moment due to the leverage effect and thus to a violent movement around the longitudinal axis and later the vertical axis of the aircraft. This effect increases the tendency of the aircraft to spin or spiral dive, which also results from the first effect above.

Thirdly, the action of the normally outboard ailerons goes out when approaching the stalled flight condition and when it is reached, i.e. if and after a stall occurs, move back early, so that large rudder deflections would be required, which in some cases still favor a stall, and the aircraft can only be controlled to a very limited extent in the border area shortly before the stall.

DISCLOSURE OF THE INVENTION

With this in mind, it is an object of the present invention to provide a tailless To provide aircraft of the above technical field with which an excessive flight condition can be controlled more easily and safely.

This object is achieved by the aircraft according to claim 1. Advantageous further developments of the invention emerge from the subclaims.

A tailless aircraft according to the invention, which has a wing with a wing nose, is characterized in that the aircraft has a flow separation edge on the wing nose, which is designed to tear off the lift-generating edge in the area of the flow separation edge at a certain angle of attack of the wing Wing to effect trending flow. The angle of attack at which the flow breaks off is generally also called the "critical angle of attack".

The flow separation edge according to the invention can ensure that a flow separation occurs in a defined manner in the area of the flow separation edge at an angle of attack predetermined by the geometry of the wing and the flow separation edge. With the flow separation edge the critical angle of attack, i.e. the angle at which the stall occurs is reduced. In other words, the flow would be able to follow the wing profile even at higher angles of attack without the flow separation edge. The flow separation edge, on the other hand, ensures that the area of the flow separation edge is the one where the flow breaks off first. Reliable flight behavior can thus be achieved in the region of the overrun flight condition and the disadvantages of the prior art of tailless aircraft with a positive swept wing are overcome.

In a preferred embodiment, the aircraft is designed as a flying wing aircraft. In other words, the aircraft is designed to be free of horizontal stabilizers and also free of vertical stabilizers. The designation of the flying wing aircraft as “free of vertical stabilizers” does not mean that the aircraft must not have any vertical surfaces such as winglets or fins. A classic rudder unit with rudder is not present in the present context in a flying wing aircraft and in this respect distinguishes the flying wing aircraft from other tailless aircraft. A flying wing aircraft has the particular advantage that practically every part of the aircraft provides lift and thus more economical operation is possible. This is due in particular to the fact that the flying wing aircraft has no or at least only very few components which generate drag but no significant lift. This is often different with conventional aircraft, since a large fuselage and large tail units are provided here. Although the hull provides a certain amount of buoyancy, depending on its construction, the hull's resistance is considerably greater. The same applies to the tail unit, which usually even generates negative lift that has to be (over) compensated for by the wings.

Preferably the aircraft has a rearward-facing, i.e. positive, wing sweep, the flow separation edge being arranged in an inner region of the wing. The inner area of the wing means in particular a wing root, that is to say a fuselage-surface transition. In the absence of an aircraft fuselage, the inner area of the wing is an area of the aircraft that is as central as possible in the transverse direction.

This preferred arrangement of the flow separation edge makes it possible to ensure that the flow separation, when approaching the covered flight condition, first begins in an area which is central in the transverse direction. This leads to the smallest possible rolling moment when the (one-sided) flow stall begins. In addition, this can cause the aircraft to show the first signs of stall (caused by the stall in the central area), while it can still be steered because the ailerons are still weak because the flow does not have to be stalled here. This arrangement of the stall edge thus makes it easier for the pilot to recognize the approach to the excessive flight condition and to initiate suitable countermeasures.

In the case of a swept wing, the arrangement of the stall edge in an inner area means that the stall affects a wing part that lies in front of the center of gravity of the aircraft, which favors tilting forward and thus the regaining of a flight condition against the flow.

In a preferred embodiment, the aircraft has, in addition to the wing, a centrally arranged fuselage, the flow separation edge being arranged in the area of a transition between the wing and the fuselage. In this embodiment, the flow separation edge is therefore in the area of the wing root. Embodiments are also conceivable in which a centrally arranged fuselage is provided which does not extend as far as the wing nose or beyond. In these cases, the flow separation edge can preferably be arranged in the central region of the (then possibly continuous) wing nose.

In this context it is further preferred that on both sides of the fuselage there is at least one flow separation edge on the wing nose is arranged. In this way the flow breaks off on both sides of the center in the transverse direction at the same angle of attack. In this way, one-sided stalling is prevented as much as possible, which significantly reduces the aircraft's tendency to tip over an area and spin.

The flow separation edge is advantageously integrated into the wing. This means that the flow separation edge is formed in one piece with the wing profile. So it is not attached to the wing as a separate part, but is part of the wing. In this way, the aerodynamic effect of the stall edge in connection with the entire aircraft, in particular the wing, can be predicted particularly well and the critical angle of attack in the area of the stall edge can be defined reliably. In addition, the resistance of the wing with the flow separation edge is kept as low as possible because the transition between the flow separation edge and the wing profile can be made flowing and very smooth.

In an advantageous embodiment, the aircraft is designed for unmanned operation. In a further advantageous embodiment, the aircraft is designed for autonomous flight operation, it being possible for the aircraft to be both unmanned and manned.

Further advantageous developments of the invention emerge from the entirety of the patent claims and the following description of the figures.

Figure list

• 1 shows the flow behavior in the stalled flight condition of a preferred aircraft;
• 2 Figure 3 is a schematic representation of a preferred aircraft;
• 3 Fig. 3 is a schematic sectional view of an airfoil with a flow separation edge;
• 4th shows an enlarged section of the wing profile 3 .

WAYS OF CARRYING OUT THE INVENTION

The following description of the figures relates to preferred embodiments of the invention, the same parts being given the same reference numerals.

1 shows the flow behavior in the stalled flight condition of a preferred aircraft 10 in a computer simulation. The plane 10 lies in a steady flow 24 in a flight condition that has a clearly positive angle of attack.

The plane 10 has a wing 12 with a wing nose 14th and winglets at both of its outer ends 20th on. It is also located on the top of the wing 12 each for about 75% of its extent from the center to the outer ends of the wing 12 a boundary layer fence 22nd to get those over the wing 12 to direct current flow.

Crosswise in the middle of the aircraft 10 there is an aircraft fuselage 16 . Between the fuselage 16 and the wing 12 A fuselage-surface transition forms, which is also known as the wing root. In the embodiment shown, this area is on both sides of the aircraft fuselage 16 a stall edge 18th in the wing nose 14th educated.

Like in the 1 is clearly visible, the flow separation edge leads 18th to do that on the plane 10 appropriate current 24 in the area of the flow separation edge 18th tears off, so no longer runs laminar over the wing surface, but turbulences 26th on the surface of the wing 12 and behind the wing 12 forms.

Through the stall edge 18th This ensures that the lift generating flow over the surface of the wing 12 deliberately tears off at an angle of attack at which the flow is otherwise still laminar over the rest of the wing 12 flows and creates buoyancy there. This has the effect that the lift at the wing root, ie relatively centrally in the transverse direction and due to the sweep of the wing 12 collapses as far forward as possible first. With that there are the ailerons 28 (see. 2 ) in the outer area of the wing 12 still effective because there is still a laminar flow here 24 is applied, the roll moment even with a one-sided stall is small and easily compensated because of the small distance to the central longitudinal axis and the small lever connected to it, and the aircraft 10 tilts forward around the transverse axis, ie it lowers its nose and can thus quickly return to a state of smaller angles of attack. The ailerons 28 are designed as so-called elevons in the embodiment shown. This is a combination of aileron and elevator ("Elevon", derived from Elevator = elevator and Aileron = aileron), which is used in tailless aircraft and enables control around the longitudinal axis and the transverse axis.

2 Figure 3 is a schematic representation of a preferred aircraft 10 . In addition to the in 1 shown elements 2 Ailerons 28 or elevons in the outer area of the wing 12 as well as a pusher propeller 30th and two cabin doors 32 .

In 2 are the stall edges 18th on both sides of the fuselage 16 highlighted to make them easier from the normal wing nose 14th to delimit.

3 Figure 3 is a schematic cross-sectional view of a profile of the wing 12 of the aircraft 10 . In the front area of the profile, i.e. on the wing nose 14th is the stall edge 18th indicated as a triangular area in cross section.

4th Figure 3 is an enlarged view of the stall edge 18th out 3 , being next to the stall edge 18th also in dashed lines the profile 34 without flow separation edge 18th is indicated. So it is easy to see how the flow separation edge 18th in the wing 12 is integrated.

The preferred aircraft makes it possible to control an excessive flight condition more easily and safely than in the case of tailless aircraft from the prior art.

Claims (8)

Aircraft (10) which is designed as a tailless aircraft (10) and has a wing (12) with a wing nose (14), characterized in that the aircraft (10) has a flow separation edge (18) on the wing nose (14), which is designed to bring about a targeted separation of the lift-generating flow over the wing (12) in the area of the flow separation edge (18) at a certain angle of attack of the wing (12). Airplane (10) after Claim 1 , wherein the aircraft (10) is designed as a flying wing aircraft. Aircraft (10) according to one of the preceding claims with rearwardly directed wing swept, wherein the flow separation edge (18) is arranged in an inner region of the wing (12). Aircraft (10) according to one of the preceding claims, wherein the aircraft (10) in addition to the wing (12) has a centrally arranged fuselage (16), the flow separation edge (18) in the region of a transition between the wing (12) and the Body (16) is arranged. Airplane (10) after Claim 4 , wherein at least one flow separation edge (18) is arranged on the wing nose (14) on both sides of the fuselage (16). Aircraft (10) according to one of the preceding claims, wherein the flow separation edge (18) is integrated into the wing (12). Aircraft (10) according to one of the preceding claims, wherein the aircraft (10) is designed for unmanned operation. Aircraft (10) according to one of the preceding claims, wherein the aircraft (10) is designed for autonomous flight operation.

Images