The present invention relates to an aircraft with wings whose maximum lift can be altered by controllable wing components. It is the purpose of the invention to reduce the structural weight of an aircraft, which reduction can be achieved in that the maximum possible load acting on the wings is limited by means of a suitable control system.
In the case of high wing loads in an aircraft it is known to achieve a reduction in the bending moment of the wings in that the outboard ailerons are adjusted so as to achieve a reduction in lift while at the same time, by way of compensation for this reduction in lift, the angle of attack of the inboard wing is increased. This known counterchange of the wing configuration requires considerable regulating effort, and in practical application has only resulted in comparatively modest savings in structural weight.
It is an object of the present invention to design an aircraft according to the precharacterising part of claim 1 such that a noticeable reduction in the structural weight of the wings can be achieved, wherein in particular in regard to gust loads the international certification regulations concerning load factors are to be taken into account.
According to the invention the object of the invention is met in that in an aircraft according to the precharacteristing part of claim 1 detectors are provided which during flight register the actual wing load at any given time, and in that a control device or regulating device is provided which then acts on the wing components, in the sense of reducing the maximum possible lift, when a predefined value of the wing load is reached.
Consequently, the design according to the invention leads to a reduction of the maximum possible wing load by forces resulting from aerodynamic lift at the expense of additional resistance. However, since this effect only takes place in those operating states in which only limited lift of the wings is required, the possible maximum load of the wing structure can be reduced in this way, and thus the structural weight can be correspondingly reduced without disregarding the safety aspects prescribed by international certification regulations.
According to the invention the wing components are then adjusted in the sense of a reduction in lift when the aircraft is above its operating point A2 (in other words the approach speed with flaps retracted) in the range of the average flight speed. Generally speaking, the effect on the wing components is opposite the normal effects, known in the state of the art, for increasing wing lift. In this process the resistance increases at the same time to the extent to which the maximum load which a wing can generate is reduced. During high flying speeds the wing components can be returned to the normal position because in these flight states the lift and thus the maximum load on the wings is anyway limited by the compressibility of the air.
According to a further embodiment of the invention, parameters such as for example speed, altitude, air path climb angle, angle of attack, etc. which are subsumed as flight state parameters in the scope of the present invention, are additionally fed to the control device or regulating device as control variables or regulating variables; and control rules or regulating rules are installed which prevent the wing components from being adjusted, in the sense of a reduction in lift, before an unstable flight state is reached. This design according to the invention makes it possible to extend as far as possible the operating range within which a reduction in the maximum possible lift of the wings is adjustable, i.e. to fully utilise the lower limit value of lift generation, which limit value has to be maintained in order to ensure safe flight and safe manoeuvrability of the aircraft.
According to another aspect of the invention, for the purpose of registering the wing load, the deflection of the wings is to be measured by means of sensors arranged at suitable positions in the wings. Such sensors can for example be wire strain gauges.
According to still another aspect of the invention, trailing-edge flaps, known per se, on the wings serving as lift-altering wing components. However, extendable stallstrips in the leading-edge region of the wings are also possible, either as an alternative or in addition.
Moreover, according to a further aspect of the invention the stallstrips are completely retractable into the contour of the wings, and the movement wells are closable by means of suitable covers. In this way it is possible to avoid additional resistance and thus loss in those operating regions where a reduction in lift is not desired.
In any case it might be advantageous if the lift-reducing components are arranged in those regions of the wings that are located away from the fuselage, because a reduction in the maximum possible forces resulting from aerodynamic lift in the outboard regions of the wings has a greater effect on bending loads than does a reduction in the inboard regions of the wings.
Below, the invention is explained with reference to the enclosed drawings, as follows:
The aircraft shown in
The curves 31, 32, 33 in the diagram according to
Analogously, the second curve 32 shows the decrease in wing load when the stallstrip 12 is extended (in
The dotted curve 33 in
Calculations relating to the wing of a large passenger aircraft have shown that if the trailing-edge flap is swivelled upward by approximately 10°, a reduction in the maximum lift of approximately 13% is achieved. The resulting additional resistance of the aircraft was approximately 5%. It can be assumed that trailing-edge adjustment in the sense of reducing maximum lift is required only during 5% of the flight time to be considered, so that the additionally generated resistance would only translate into a reduction of 0.25% in the flying range of the aircraft. On the other hand, calculations show that the 13% load reduction would return a reduction in the weight of the wing, which reduction because of the correspondingly increased fuel tank capacity would translate into a gain of 2% in the flying range. A comparison shows that a large passenger aircraft designed according to the invention could achieve a net gain of approximately 1.7% in its flying range.
Number | Date | Country | Kind |
---|---|---|---|
10 2004 045 732.8 | Sep 2004 | DE | national |
This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/631,302 filed Nov. 29, 2004 and of German Patent Application No. 10 2004 045 732.8 filed Sep. 21, 2004, the disclosure of both applications is hereby incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP05/10228 | 9/21/2005 | WO | 00 | 3/16/2007 |
Number | Date | Country | |
---|---|---|---|
60631302 | Nov 2004 | US |