GB2129748A

GB2129748A - Device for reducing squall loads on aircraft wings

Info

Publication number: GB2129748A
Application number: GB08326941A
Authority: GB
Inventors: Heinz Gunter Klug
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1982-11-10
Filing date: 1983-10-07
Publication date: 1984-05-23
Also published as: GB8326941D0; DE3241456A1; FR2535678A1; GB2129748B

Abstract

In an aircraft having airfoil wings 10 provided with flaps or passages, there are provided, over the outer portion 10c of the wing 10, slot-like narrow flow channels 11 from the underside to the upper side of the wing structure 10, so arranged and designed that the gust lift is nullified, such channels being controlled by respective flaps 12. The flaps 12 may be opened by a gust- sensing system, or by the pressure differential between the lower and upper sides of the wing exceeding a predetermined value. Upward airflow through the channels 11 causes upper surface flow separation aft of the channels, with consequent reduction of lift. <IMAGE>

Description

SPECIFICATION Device for reducing squall loads on aircraft wings This invention relates to a device or arrangement for reducing squall loads (or gust loads or turbulence loads) in the case of aircraft the airfoil wings of which are provided with flaps or passages.

Such an arrangement is already known from German Offenlegungsschrift No. 25 33 221, in which flaps on the wings open upon increase in lift loading and close upon reduction thereof. The action of this solution is based on the fact that the opening of the passages serves to reduce considerably the effective wing area. The main disadvantage of this solution is to be seen in that a wing designed in this way is too expensive, complex and complicated and scarcely feasible for practical use. The proposed measures comprising an arrangement of a number of flaps which are coupled together by means of a pull connection and which cover one or more wide gaps in the wing root region are not realisable for modern aircraft.

Disclosed by German Aislegeschrift No. 1481 931 is a control device for aircraft, wherewith the problem is solved of eliminating the disturbing moments, which act in a counter-curve sense, in the case of an aircraft, with an increase in lift by blowing-out air over the trailing wing edges. This solution functions only in conjunction with a blow-out mechanism, in which the requisite amounts of air are supplied by a compressor.

The problem underlying the present invention is to provide a device or arrangement of the kind mentioned at the beginning hereofwith which squall loads are reduced in a simple, reliable way which acts without delay.

To solve this problem, the present invention provides a device for reducing squall loads in the case of aircraft the airfoil wings of which are provided with flaps or passages, characterised by the provision in the wing structure, from the front underside to the upper side thereof, one or more fissure-like rigid flow ducts provided with flaps which automatically open the flow duct upon an upwards gust. Further optical features of the invention are set out in the features of claims 2 to 6 appearing at the end of this specification.

An exemplified embodiment of the device of the invention is discussed in the following description and shown schematically in the accompanying drawing in which: Figure 1 is a top perspective view illustrating a wing according to the invention; Figure 2 is an enlarged cross-section taken along the line A-A of Figure 1, showing the closed flap position; and Figure 3 is a cross-section corresponding Figure 2 but showing the opened flap position.

The dimensioning of the wings of a modern commercial plane or passenger aircraft is determined, to a substantial extent, by the square loads (or gust loads of turbulence loads) that are to be absorbed. Perforce these forces involve increased expenditure on structural weight and accordingly also increased fuel consumption. This led to the: development of so-called gust load reduction systems, which, however, measure the gustitselforthe effect thereof; then, by way of regulators, control surfaces are so swung that the aerodynamic loads are reduced. Proposed as control surfaces for this purpose are: ailerons, landing flap segments and individual spoilers, with which critical upward gusts are countered by symmetrical deflection and the lift is reduced.

In the case of present-day modern aircraft designs with their typical "torsion-soft" high extension wings, the aileron and landing flap deflections lead to elastic distortion of the wing, whereby a considerable part of the effect to be achieved is immediately lost. The previous attempts with spoilers display a non-linear characteristic. In the case of all previously-used surfaces there resulted difficulties from the high actuating speeds, the values of which lie at 5 Ibs, = 1 00"/sex. Moreover, the inertia forces become camparable with the aerodynamic forces.

All these previous difficulties are obviated in a surprisingly simple manner in that preferably in the outer region 1 Oc of the wing structure 10 one or more fissure-like flow ducts 11 are arranged, which are conducted from the underside 1 0a of the wing to the upper side lOb of the wing and form a secure, firm or fixed component part of the wing structure.

These flow ducts 11 have, on the underside 10a of the wing a certain intake curvature 1 1a, whereas they merge, on the upper side lOb of the wing, into a straight line 1 ib extending almost perpendicular to the outside-air incident flow direction. Each of these flow ducts, designed in this way, is sealed, in undisturbed normai flight, buy a narrowflap 12. If now a gust occurs and increases the lift, then the flap is opened and thus a flow-through occurs through the ducts 11 at the outlet of which on the wing upper side 10b of which is formed an areal or laminar jettransversely to the incident flow direction of the outer air, which jet acts like a spoiler.This leads to separation or detachment of the incident flow and thus to decrease in the additional lift which would be caused by the gust.

The opening and closing of the flaps 12 can now be effected in various ways. On the one hand this can be effected under the control of a regulator or governor, in which event various systems are:con- ceivable, for example an independent pressure regulator or a regulator which is acted upon by the aircraft electronics or other equipment. By means of such systems active load diminution is achieved. On the other hand, what prove themselves for the so-called "passive" load diminution are systems in which the flap automatically opens under a specific bias when specific pressure differences and the underside thereof are exceeded; in other words when a specific lift value is reached.Furthermore, by suitable coordination of the centre of gravity of the flap to the axis of rotation of such flap, besides the pressure difference, also the acceleration actually experienced by the wing can be enlisted for flap control.

Naturally it is possible to incorporate the aforedescribed device into the complete flight control in order to take over the roll controlling function of the usual spoilers.

The above-described device has, as compared with conventional rudder and flap arrangements, a series of advantages. Thus, in a load diminution system, slight inertial moments of the control surfaces occur; the action loss through the elastic twisting of the wing is considerably less; the linear characterstic is considerably improved as compared with a mechanical spoiler; and a genuine passive load diminution is rendered possible.

In the case of the design as a so-called roll control element, the slight inertia moments prove to be advantageous as equally are the slight aerodynamic loads on the acutator.

Claims

1. A device for reducing squall loads in the case of aircraft the airfoil wings of which are provided with flaps or passages, characterised by the provision in the wing structure, from the front underside to the upper side thereof, one or more fissure-like rigid flow ducts provided with flaps which automatically open the flow duct upon an upwards gust.

2. A device as claimed in claim 1, characterised in that the flow ducts are each arranged in the outer region of the wing.

3. A device as claimed in claim 1 or 2, characterised in that the opening of the flow ducts in begining and duration is triggered by a specific pressure difference value being exceeded.

4. A device as claimed in claim 1 or 2, characterised in that the opening of the flow ducts is performed by a regulator.

5. A device as claimed in any preceding claim charaterised in that the acceleration experienced by the wing is enlisted for control of the flaps by reason of association of the centre of gravity of the flap to the axis of rotation of the flap.

6. A device as claimed in any preceding claim characterised in that the fissure-like flow ducts merge from a lower initial curvature into a straight line which extends almost perpendicular to the outside air or the incident flow direction thereof.

7. A device for reducing squall loads in aircraft wings substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.