GB2100684A

GB2100684A - Flap arrangement for the leading edge of an aircraft wing

Info

Publication number: GB2100684A
Application number: GB08215918A
Authority: GB
Inventors: Werner Staudacher
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1981-06-04
Filing date: 1982-06-01
Publication date: 1983-01-06
Also published as: DE3122137C2; FR2507148B1; FR2507148A1; DE3122137A1; GB2100684B

Abstract

A flap arrangement for the leading-edge of an aircraft wing 10 comprises two flaps K1, K2 which are arranged behind one another and by means of which the distribution of S-shaped curved eddy currents over the wing 10 can be adjusted, in which respect the front flap K1 is swingable upwards and downwards and the rear flap K2 is only swingable downwards. Applicable to delta, double delta, and swept wings generating leading edge separated vortices. <IMAGE>

Description

SPECIFICATION Flap arrangement for the leading edge of an aircraft wing This invention relates to a flap arrangement for the leading edge of an aircraft wing, or such as a delta wing, a double-delta wing, a curved wing or swept-back wing, which is subject to separated or disjointed leading-edge eddy vortexes or currents.

Such flap arrangements are known 'per se' in various embodiments. If it is a matter, in the respect, of a slim highly-swept-back wing ground plan (a 50 ), then there arise, as from a specific angle of incidence, stable eddy currents which emanate from the leading edge of the flap and which develop-as shown by Fig. 1 ainto spirally rolled-up cone shaped eddies. This leads to an appreciable non-linear increase in lift (A Av) which increases with an increase in the angle of incidence and which is accompanied by a growth in resistance or drag (A Wv) because a simultaneously increasing loss of leading-edge suction force arises.

The origin of this leading-edge detachment or separation of the eddy currents is controlled by conventional leading-edge flaps, as is known from the prior art, in which respect a deflection of the flaps downwards leads to smaller effective angles of incidence (Fig. 2a) and a deflection upwards leads to higher effective angles of incidence (Fig. 2b), which in turn leads to drag-reducing or lift-increasing effects respectively.

However, for a specific angle or incidence, it is not possible and also not desirable to produce drag-optimum conditions by increasing the negative leading-edge deflection. The separation of eddy currents is effected no longer from the leading edge, but as shown in Fig. 3-from a so-called flap knee, which has the severest curvature of the wing contourl. There then arise analagous conditions as are shown in Fig. 1 in the event of the nose flap not being deflected.

The underpressures produced by the eddy currents act on the upper side of the rest of the wing as additional force. The components of this additional force are additional lift and additional drag, as shown by the vector diagram in Fig. 1.

The problem underlying the present invention is to provide a flap arrangement wings, of the kind mentioned at the beginning hereof, which avoids the disadvantages of the known arrangements in accordance with the prior art and with which it is possible both to control the separation of the eddy currents and to fix the separation region thereof on the wings.

This problem is solved in that the present invention provides a flap arrangement for the leading-edge of an aircraft wing, such as a delta wing, a double-delta wing, a curved wing or swept-back wing, which is subject to separated or disjoined leading edge eddy vortexes or currents, characterised in that the flap arrangement is split into two flaps along its length and is an integral consistuent part of the wing, in which respect: a) in its front part of the wing an s-shaped curved distribution of eddy currents is adjustable by appropriate adjustment of the flaps.

b) the front flap is movable upwards and downwards, and c) the rear flap is only movable downwards.

With the proposed arrangement in view of a decoupling of the geometric angle of incidence, the separation of the eddy currents is so controlled that optimum drag conditions are realised up to higher geometric angles of incidence and non-linear additional lift can be produced even in the case of fairly low geometric angles of incidence. Furthermore, a socalled eddy separation region can be influenced in its extend along the length and span (or width) of the wing.

The invention will be described further, by way of example, with reference to the accompanying drawings in which: Figure la is a perspective view of eedies or vortices arising at the leading edge of a known flap arrangement; Figure ib is a section along the line A-A in accordance with Fig. 1 a and a vector diagram for the section; Figure 2a is a section through a wing in which respect its flap is deflected or extended downwards, and illustrates the flow conditions around the wing and flap caused by a large angle of incidence; Figure 2b is a view similar to that of Fig. 2a but in which the flap is extended upwards; Figure 3 is a view similar to that of Figs. 2a and 2b but illustrating the formation of the eddy at a flap knee;; Figure 4a is a londitudinal-section of the preferred flap arrangement of the invention with the flaps in the downwardly-extended state from the wing; Figure 4b is a view similar to that of Fig. 4a but with the flaps in the upwardly-extended state and with a vector diagram; Figure 5 is a view similar to that of Fig. 4a but illustrating the positional control of the leading-edge eddy; Figure 6a is a side view of the wing and flap arrangement; Figure 6b is a side view of the wing and flap arrangement with the flaps extended downwards; Figure 6c is a side view of the wing and flaps over which flows an S-shaped curved eddy currents; Figure 7a is a plan view of a delta wing with a continuous leading-edge flap; Figure 7b is a plan view of a wing adjoint piece or attachment bent or elbowed in the front part of the wing;; Figure 7c is a plan view of a further wing shape with an appropriate leading-edge flap arrangement in accordance with the invention; Figure 7d is a plan view of a fourth wing shape with an appropariate leading-edge flap arrangement in accordance with the invention and Figure 7e is a plan view of a fifth wing shape and an appropariate leading-edge flap arrangement in accordance with the invention The preferred flap arrangement of the invention as illustrated in Figs. 4a to 7e comprises two flaps K, and K2, of lengths t1, t respectively, and is an integral consituent part of a wing 10, in which respect an s-shaped curved air flow distribution can be produced in the front part of the wing 10 by appropriate adjustment of the flaps K, and K2. In this respect front flap K, is swingable both upwardly and downwardly.Rear flap K2, on the other hand, is only movable downwards. In Fig. 4b is shown the undesired eddy currents that occur--exactly as is the case with the flap arrangement of the prior art if the flap K2 is extended upwardly. In this case, the eddy currents produce, precisely as in the case of the so-called flap knee (Fig. 3), underpressures which act on the rest of the wing in addition to the normal forces.

The front flap K is shorter in length than the flap K2. Both flaps K,, K2 are connected together and are mutually twistable in known 'per se' manner through a hinge connection, in which respect the hinges' rotary shaft or axis is mounted in hinge eyes. The control of flaps K1, K2 takes place in similarly known manner through a normal flap control arrangement. Through the coordination of the flaps K,, K2 and their respective lengths t,, t2, a control and check of the position and severity of the eddy currents about the wing 10 is achieved. Through this coordination it is possible to cause an underpressure to act on the downwardy-extended second flap K2. The underpressure is produced by controlled eddy currents on the upper side of the wing 10 and acts normal to the flap surface.At the same time, the reabutment line or re-contiguity line "W" if the eddy current can be placed into the vicinity of flap knee 11, so that a possible normal component on the part of the wing 10 lying therebehind-as shown in Fig. 5-is minimized.

The separation areas, that occur in the flap arrangements of the prior art and that are illustrated in Fig. 3, are achieved, in a manner favourable to lift and drag, by the re-orientation, now made possible, of the eddy currents in the sense of a synergetic effect. Simulataneously with the described preferred arrangement a considerably better lift-drag ratio (or gliding ratio) A/W is attained.

The preferred flap arrangement can be used both for slim, highly-sweptback wing ground plans (delta and sweptback wings) and for highly-sweptback parts of composite (or compound or complex) wing ground plans (hybrid wings, curved wings and double-delta wings).

Exemplified embodiments of these wings are shown in Figs. 7ato 7e.

The formulae in the Figures do not require any detailed explanations. Designation by W, is eddy drag, designated by Nv is the normal force and by A the lift. w7K, and a7K2 denote the respective flap extension angles and c1, c2, c1, and c2, are geometric characteristic magnitudes of flap length.

As a result of the proposed measures, the arising additional force is converted by a combination of the leading-edge flap extensions into a component contrary to the drag, in that the eddy currents are conducted along the leading-edge flaps and appropriately controlled.

Claims

1. A flap arrangement for the leadingedge of an aircraft wing, such as a delta wing, a double delta-wing, a curved wing or sweptback wing, which is subject to separated or disjoined leading-edge eddy vortexes or currents, characterised in that the flap arrangement is split into two flaps along its length and is an integral constituent part of the wing, in which respect a) in its front part the wing an s-shaped curved distribution of eddycurrents is adjustable by appropriate adjustment of the flaps b) the front flap is movable upwards and downwards, and c) the rear flap is only movable downwards.

2. A flap arrangement as claimed in claim 1, characterised in that the front flap is shorter in length than the rear flap.

3. A flap arrangement as claimed in claim 1 and 2, characterised in that the eddy of vortex currents produce a reabutting flow close to a rear flap knee.

4. A flap arrangement for the leading edge of an aircraft wing substantially as hereinbefore described with reference to and as illustrated in Figs. 4a to 7e of the accompanying drawings.