Patent Description:
The aerodynamic surface comprises a skin, a stiffener arrangement, and an acoustic filler arrangement. The skin extends in a span direction from an inboard end to an outboard end and extends in a chord direction from a leading edge to a trailing edge. The skin includes a first skin portion, preferably an upper skin portion, and a second skin portion, preferably a lower skin portion. Both first and second skin portions extend from the leading edge to the trailing edge and together surround an interior of the aerodynamic surface from opposite sides.

The stiffener arrangement arranged is in the interior for stiffening the first and second skin portions and includes at least an inboard stiffener in the area of the inboard end and/or an outboard stiffener in the area of the outboard end. Preferably, both the inboard stiffener and the outboard stiffener extend in the chord direction, preferably in a chord plane. At the inboard end between the first skin portion, the second skin portion and the inboard stiffener an inboard cavity is formed. Additionally or alternatively, at the outboard end between the first skin portion, the second skin portion and the outboard stiffener an outboard cavity is formed.

The acoustic filler arrangement includes multiple filler elements and is arranged or received within the inboard cavity and/or within the outboard cavity for reducing noise generated at the inboard cavity and/or at the outboard cavity. The noise is usually generated by sharp lateral edges of the first and second skin portions upstream from the inboard and/or outboard cavity which cause vortices that in turn are responsible for an undesired broadband noise. Additionally, the noise is generated by resonance within the inboard and/or outboard cavity which acts as a Helmholtz resonator that may cause undesired tonal and broadband noise.

Similar aerodynamic surfaces are known in the art, such as flaps, where various attempts have been made in the art to fill the cavities at the flap side edges in order to reduce unpleasant noise. In one attempt the cavities have been filled by solid filler elements with a smooth outer surface. Such filler elements were able to reduce resonance within the cavities and the resulting noise. However, partial broadband noise still remained as the sharp lateral edges of the first and second skin portions upstream the cavities were still present. Thus, in another attempt the cavities have been filled by foam filler elements with a porous outer surface. Such filler elements were able to reduce also the broadband noise by the sharp lateral edges being softened by the porous edges of the filler elements. However, the foam filler elements are difficult to produce, install and maintain at a small scale or complex shape, such as in the area of the leading edge or the trailing edge of the aerodynamic surface.

<CIT> discloses a flap for operatively coupling to a wing main element of an aircraft, the flap comprising: an outer flap section having a side edge portion that at least partially surrounds a flap side-edge cavity; and a porous cavity-filler insert positioned in the flap side-edge cavity. The porous cavity-filler insert can have a lower channel formed therein, whereby the flap further includes a seal disposed in the lower channel. The seal seats against the wing when the flap is a the retracted position to prevent airflow between the side edge portion of the flap and the wing.

Other aircraft control surfaces with noise-reducing/-attenuating portions are known from <CIT>, <CIT> and <CIT>.

Therefore, the object of the present invention is to provide an aerodynamic surface enabling both efficient noise reduction and convenient and cost-efficient handling.

This object is achieved with the movable aerodynamic surface according to independent claim <NUM>, wherein the acoustic filler arrangement has a hybrid form including at least one first type filler element with a smooth, non-porous outer surface and at least one second type filler element with a porous outer surface. In this connection the term "outer surface" relates to at least the lateral surface of the filler elements facing out of the inboard cavity and/or out of the outboard cavity, i.e. the surface transverse or perpendicular to the span direction and facing laterally away from the interior of the aerodynamic surface. The term "outer surface" might also relate to the entire outer surface of the first and/or second type filler elements. Such a hybrid acoustic filler arrangement combines the advantages of both types of filler elements, i.e. of the smooth outer surface and the porous outer surface. The parts of the cavities that are sufficiently large and simple shaped are filled with the second type filler elements to achieve sufficient reduction of tonal and broadband noise, while the smaller and more complex shaped parts of the cavities are filled with the first type filler elements to allow cost-efficient production, installation and maintenance as well as convenient handling of the related filler elements. This allows that all noise due to resonance and most of the noise due to vortices can be widely reduced, while costs and effort are kept at a reasonable level.

According to a preferred embodiment, the acoustic filler arrangement includes one or more further first type filler elements and/or second type filler elements. In such a way, different parts of the cavities can be filled with different types of filler elements.

According to a further preferred embodiment, the acoustic filler arrangement is arranged in the inboard cavity and/or in the outboard cavity in such a way that the entire inboard cavity and/or outboard cavity is filled, i.e. all parts of the inboard cavity and/or outboard cavity are filled. This leads to efficient reduction of the resonance noise.

According to a further preferred embodiment, the acoustic filler arrangement is arranged in the inboard cavity and/or in the outboard cavity in such a way that the outer surfaces, in particular the lateral surfaces facing out of the inboard cavity and/or out of the outboard cavity, of the first and second type filler elements extend in the same plane, which is preferably the same plane in which at least some of the lateral edges of the first and second skin portions extend and which preferably extends transversely or perpendicularly to the span direction. In such a way, the inboard cavity and/or the outboard cavity is preferably fully and continuously filled with the filler elements which form a continuous and smooth common lateral surface, preferably together with the lateral edges. This further improves noise reduction.

According to a further preferred embodiment, at the inboard end and/or at the outboard end, i.e. at the lateral edges, the first skin portion and/or the second skin portion has at least one cut-out, i.e. a recess, in the area of the second type filler element, preferably in a central area of the inboard and/or outboard cavity. , the lateral edge of the first and/or second skin portion does not extend in the same plane as the porous outer surface of the second type filler element but instead is recessed or setback in the span direction relative to the porous outer surface of the second type filler element. In such a way, there are no sharp lateral edges present in the area of the cut-out, but rather porous lateral edges of the second type filler element, which largely reduce vortices and thus broadband noise. The cut-outs preferably have a depth, i.e. a span extension, of between <NUM>% and <NUM>%, preferably between <NUM>% and <NUM>%, most preferred about <NUM>%, of the maximum profile thickness of the aerodynamic surface. The cut-outs might not extend along the entire chord extension of the second type filler element, so that there is a non-cut out area at both chord ends of the second type filler element for a better hold of the second type filler element. The cut-outs might have edges extending in chord direction and parallelly spaced from the lateral surface.

According to a further preferred embodiment, the first type filler element is formed, preferably entirely formed, of a non-porous, solid material, which is preferably lightweight and resistant, such as plastic or metal, preferably aluminium, titanium or polymeric resin, which might or might not have a hollow inside. This relates to a very simple and efficient design. The first type filler element and/or the second type filler element can be fixed in the inboard cavity and/or in the outboard cavity by adhesive and/or by mechanical retainers, such as bolts.

According to a further preferred embodiment, the second type filler element is formed, preferably entirely formed, of a porous material, preferably of a foam. This relates to a very simple and efficient design.

In particular, it is preferred that the porous material is an acoustic noise reduction foam, such as a metal foam or a plastic foam. This material allows efficient noise reduction.

According to a preferred embodiment, the inboard cavity and/or the outboard cavity is divided in multiple cavity sections separated from one another by one or more cavity walls. Such cavity walls are provided e.g. for stiffening or as a guide rail for receiving a guide roller, such as a so-called fish mouth of a flap.

In particular, it is preferred that each cavity section is filled with at least one first type filler element and/or second type filler element. Thus, no cavity section remains unfilled which improved noise reduction.

It is also preferred that at least one cavity is filled with both at least one first type filler element and at least one second type filler element. Thus, two different type filler elements are arranged in one common cavity section, which might be required, e.g., near edges or corners.

According to a preferred embodiment, at least one, preferably two, first type filler elements are arranged in the cavity in the area of the leading edge. At least one second type filler element is arranged in the cavity in a central area. At least one first type filler element is arranged in the cavity in the area of the trailing edge. In such a way, the small and complex shapes at the leading edge and the trailing edge are filled with the more convenient first type filler elements, while the central area can be filled with the more complex porous second type filler element. This relates to a very simple design and effective noise reduction.

It is preferred that the cavity comprises at least one front cavity section in the area of the leading edge and a rear cavity section in the area of the trailing edge and preferably also in a central area. Preferably, two front cavity sections are arranged in the area of the leading edge, preferably on opposite sides of a guide rail for receiving a guide roller, such as a so-called fish mouth of a flap. The at least one front cavity section, preferably each of the two front cavity sections, is filled with at least one first type filler element. The rear cavity section is filled with at least one first type filler element arranged in the area of the trailing edge and preferably having a wedge shape, and at least one second type filler element arranged upstream from the at least one first type filler element arranged in the area of the trailing edge. In such a way, the second type filler element is arranged between at least two first type filler elements arranged at the leading edge and the trailing edge. This relates to a very simple design and effective noise reduction.

According to a preferred embodiment, the aerodynamic surface is formed as a high lift flap, i.e. a trailing edge flap, movably mounted to the trailing edge of a wing for an aircraft. Alternatively, the aerodynamic surface might be formed as another high lift surface, such as a slat, or as a control surface, such as an aileron, a rudder or an elevator. Reducing the noise originating from the flap side edges largely reduces the overall noise during take-off and approach of an aircraft.

A further aspect of the invention relates to a wing for an aircraft comprising the aerodynamic surface according to any of the afore-described embodiments. Alternatively, the aerodynamic surface might be part of the vertical tail plane or the horizontal tail plane. The features and effects described above in connection with the aerodynamic surface apply vis-à-vis also to the wing.

A further aspect of the invention relates to an aircraft comprising the aerodynamic surface according to any of the afore-described embodiments, and/or comprising the wing according to any of the afore-described embodiments. The features and effects described above in connection with the aerodynamic surface and the wing apply vis-à-vis also to the aircraft.

Hereinafter, a preferred embodiment of the invention is described in more detail by means of a drawing. The drawing shows in.

In <FIG> an aircraft <NUM> according to the invention is illustrated. The aircraft <NUM> has a fuselage <NUM>, wings <NUM>, a vertical tail plane <NUM> and a horizontal tail plane <NUM>. Each wing <NUM> comprises a main wing <NUM> and at least one movable aerodynamic surface <NUM> in the form of a high lift flap <NUM> mounted to the trailing edge of the main wing <NUM> movably between a retracted position and an extended position.

As shown in <FIG>, the aerodynamic surface <NUM> comprises a skin <NUM>, a stiffener arrangement <NUM>, and an acoustic filler arrangement <NUM>. The skin <NUM> extends in a span direction <NUM> from an inboard end <NUM> to an outboard end <NUM> and extends in a chord direction <NUM> from a leading edge <NUM> to a trailing edge <NUM>. The skin <NUM> includes an upper, first skin portion <NUM> and a lower, second skin portion <NUM>. Both first and second skin portions <NUM>, <NUM> extend from the leading edge <NUM> to the trailing edge <NUM> and together surround an interior <NUM> of the aerodynamic surface <NUM> from opposite upper and lower sides.

The stiffener arrangement <NUM> arranged is in the interior <NUM> for stiffening the first and second skin portions <NUM>, <NUM> and includes an inboard stiffener <NUM> in the area of the inboard end <NUM> and an outboard stiffener (not shown) in the area of the outboard end <NUM>. Both the inboard stiffener <NUM> and the outboard stiffener extend in the chord direction <NUM>. However, only the inboard end <NUM> is shown in the Figures, so that the invention is described hereinafter only with reference to the inboard end <NUM>, although the outboard end <NUM> might be formed in the same way as the inboard end <NUM>. At the inboard end <NUM> between the first skin portion <NUM>, the second skin portion <NUM> and the inboard stiffener <NUM> an inboard cavity <NUM> is formed.

The acoustic filler arrangement <NUM> includes multiple filler elements <NUM> and is arranged within the inboard cavity <NUM> for reducing noise generated at the inboard cavity <NUM>. The noise is usually generated by sharp lateral edges <NUM> of the first and second skin portions <NUM>, <NUM> upstream from the inboard cavity <NUM> which cause vortices that in turn are responsible for an undesired broadband noise. Additionally, the noise is generated by resonance within the inboard cavity <NUM> which acts as a Helmholtz resonator that may cause undesired tonal and broadband noise.

As shown in <FIG>, the acoustic filler arrangement <NUM> has a hybrid form including three first type filler elements <NUM>' with a non-porous, smooth outer surface <NUM> and one second type filler element <NUM>" with a porous outer surface <NUM>.

The acoustic filler arrangement <NUM> is arranged in the inboard cavity <NUM> in such a way that the entire inboard cavity <NUM> is filled, i.e. all parts of the inboard cavity <NUM> are filled. The acoustic filler arrangement <NUM> is arranged in the inboard cavity <NUM> in such a way that the smooth outer surfaces <NUM> of the first type filler elements <NUM>', in particular the lateral surfaces <NUM> facing out of the inboard cavity <NUM>, extend in the same plane as the lateral edges <NUM> of the first and second skin portions <NUM>, <NUM>. In such a way, the inboard cavity <NUM> is fully and continuously filled with the filler elements <NUM> which form a continuous and smooth common lateral surface <NUM> together with the lateral edges <NUM> in the area of the first type filler elements <NUM>'. However, cut-outs <NUM> are provided in the first and second skin portions <NUM>, <NUM> in the area of the second type filler element <NUM>", which will be described in more detail further below.

The first type filler element <NUM>' is entirely formed of a non-porous, solid material, in the present embodiment aluminium, which has a hollow inside. The second type filler element <NUM>" is entirely formed of a porous material in the form of an acoustic noise reduction foam, in the present embodiment a metal foam. Both first and second type filler elements <NUM>', <NUM>" are fixed in the inboard cavity <NUM> by bolts <NUM>.

The inboard cavity <NUM> is divided in multiple cavity sections <NUM> separated from one another by several cavity walls <NUM>. Each cavity section <NUM> is filled with at least one first type filler element <NUM>' or second type filler element <NUM>". One cavity section <NUM> is filled with both one first type filler element <NUM>' and one second type filler element <NUM>".

As shown in <FIG>, the inboard cavity <NUM> comprises two front cavity sections <NUM> in the area of the leading edge <NUM> which are arranged on opposite sides of a so-called fish mouth <NUM> of the flap <NUM>, which refers to a guide rail for receiving a main wing based guide roller for guiding the aerodynamic surface <NUM> during extension or retraction movement. The inboard cavity <NUM> further comprises a rear cavity section <NUM> extending in the area of the trailing edge <NUM> and also in a central area <NUM>. Each of the two front cavity sections <NUM> is filled with one first type filler element <NUM>'. The rear cavity section <NUM> is filled with one first type filler element <NUM>' arranged in the area of the trailing edge <NUM> and having a wedged shape, and one second type filler element <NUM>" arranged upstream from the trailing edge <NUM> and the related first type filler element <NUM>'. In such a way, the second type filler element <NUM>" is arranged in a central area <NUM> between at least two first type filler elements <NUM>' arranged at the leading edge <NUM> and the trailing edge <NUM>.

As shown in <FIG>, cut-outs <NUM> are formed in the first and second skin portions <NUM>, <NUM> in the area of the second type filler element <NUM>", i.e. in area of the rear cavity section <NUM> in the central area <NUM> of the inboard cavity <NUM>. Specifically, the lateral edge <NUM> of the first skin portion <NUM> has a cut-out <NUM> in the area of the second type filler element <NUM>", as shown in <FIG>, and the lateral edge <NUM> of the second skin portion <NUM> has a cut-out <NUM> in the area of the second type filler element <NUM>", as shown in <FIG>. This means, the lateral edges <NUM> of the first and second skin portions <NUM>, <NUM> do not extend in the same plane as the porous outer surface <NUM> of the second type filler element <NUM>" and, thus, of the lateral surface <NUM>, but instead are recessed in the span direction <NUM> relative to the porous outer surface <NUM> of the second type filler element <NUM>", so that there are no sharp lateral edges <NUM> present in the area of the cut-out <NUM>, but rather porous lateral edges of the second type filler element <NUM>", which largely reduce vortices and thus broadband noise. The cut-outs have a depth, i.e. a span extension, of about <NUM>% of the maximum profile thickness of the aerodynamic surface <NUM>. The cut-outs <NUM> in the present embodiment do not extend along the entire chord extension of the second type filler element <NUM>", so that there is a non-cut out area <NUM> at both chord ends of the second type filler element <NUM>" for a better hold of the second type filler element <NUM>". The cut-outs <NUM> in the present embodiment have edges extending in chord direction <NUM> and parallelly spaced from the lateral surface <NUM>.

Although not shown in the Figures, the outboard end <NUM> of the aerodynamic surface <NUM> might be formed in the same way as the inboard end <NUM>, including an outboard cavity (not shown) formed similar as the inboard cavity <NUM> and filled with an acoustic filler arrangement <NUM> as described above in connection with the inboard cavity <NUM>.

Claim 1:
A movable aerodynamic surface (<NUM>) for an aircraft (<NUM>), comprising
a skin (<NUM>) extending in a span direction (<NUM>) from an inboard end (<NUM>) to an outboard end (<NUM>) and extending in a chord direction (<NUM>) from a leading edge (<NUM>) to a trailing edge (<NUM>), wherein the skin (<NUM>) includes a first skin portion (<NUM>) and a second skin portion (<NUM>) both extending from the leading edge (<NUM>) to the trailing edge (<NUM>) and together surrounding an interior (<NUM>) from opposite sides, and
a stiffener arrangement (<NUM>) arranged in the interior (<NUM>) for stiffening the first and second skin portions (<NUM>, <NUM>) and including at least an inboard stiffener (<NUM>) in the area of the inboard end (<NUM>) and/or an outboard stiffener in the area of the outboard end (<NUM>),
wherein at the inboard end (<NUM>) between the first skin portion (<NUM>), the second skin portion (<NUM>) and the inboard stiffener (<NUM>) an inboard cavity (<NUM>) is formed, and/or at the outboard end (<NUM>) between the first skin portion (<NUM>), the second skin portion (<NUM>) and the outboard stiffener an outboard cavity is formed,
wherein an acoustic filler arrangement (<NUM>) including multiple filler elements (<NUM>) is arranged within the inboard cavity (<NUM>) and/or the outboard cavity for reducing noise generated at the inboard cavity (<NUM>) and/or at the outboard cavity,
wherein
the acoustic filler arrangement (<NUM>) has a hybrid form including at least one first type filler element (<NUM>') with a smooth outer surface (<NUM>) and at least one second type filler element (<NUM>") with a porous outer surface (<NUM>).