U.S. patent application number 09/837638 was filed with the patent office on 2001-11-08 for aerodynamic noise reducing structure for aircraft wing slats.
Invention is credited to Carl, Udo, Gleine, Wolfgang, Mau, Knut.
Application Number | 20010038058 09/837638 |
Document ID | / |
Family ID | 7639176 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038058 |
Kind Code |
A1 |
Gleine, Wolfgang ; et
al. |
November 8, 2001 |
Aerodynamic noise reducing structure for aircraft wing slats
Abstract
A hollow expandable and contractible displacement element is
secured onto the concave rear surface of a slat facing the leading
edge of an aircraft wing. A bleed air line supplies engine bleed
air into the hollow displacement element to selectively expand or
contract the displacement element, which is preferably elastically
expandable. When the slat is extended, the displacement element is
expanded to fill-out the concave cavity on the rear surface of the
slat so as to prevent formation of a vortex in the slat air gap and
thereby to reduce aero-acoustic noise. When the slat is retracted,
the displacement element is contracted to be conformingly
accommodated in the sickle-shaped space between the slat and the
leading edge of the wing.
Inventors: |
Gleine, Wolfgang;
(Kakenstorf, DE) ; Mau, Knut; (Hamburg, DE)
; Carl, Udo; (Hamburg, DE) |
Correspondence
Address: |
FASSE PATENT ATTORNEYS, P.A.
P.O. BOX 726
HAMPDEN
ME
04444-0726
US
|
Family ID: |
7639176 |
Appl. No.: |
09/837638 |
Filed: |
April 17, 2001 |
Current U.S.
Class: |
244/198 |
Current CPC
Class: |
B64C 2230/20 20130101;
B64C 2230/06 20130101; Y02T 50/30 20130101; B64C 3/46 20130101;
B64C 2230/14 20130101; Y02T 50/32 20130101; B64C 9/24 20130101;
Y02T 50/10 20130101; B64D 15/04 20130101; Y02T 50/14 20130101; Y02T
50/166 20130101 |
Class at
Publication: |
244/198 |
International
Class: |
B64C 003/00; B64C
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 17, 2000 |
DE |
100 19 185.1 |
Claims
What is claimed is:
1. In an aircraft including a source of a pressurized fluid and a
wing arrangement, wherein said wing arrangement includes a wing
body and a slat, said wing body terminates forwardly in a leading
edge nose of said wing body, said slat has a concave rear surface
facing toward said leading edge nose, and said slat is movably
connected to said wing body to be movable between a retracted slat
position in which said slat is adjacent to said leading edge nose
with said concave rear surface facing and adjacent to said leading
edge nose and an extended slat position in which said slat is
spaced away from said leading edge nose with a slat air gap bounded
between said slat and said leading edge nose, an improvement for
reducing aero-acoustic noise generated by said wing arrangement,
wherein said improvement comprises: a hollow displacement element
that encloses at least one hollow space therein and that is
arranged and secured on said concave rear surface extending along
said slat, and a pressurized fluid line arrangement connecting said
at least one hollow space to said source of a pressurized
fluid.
2. The improvement in the aircraft according to claim 1, wherein
said source of a pressurized fluid comprises an aircraft bleed air
system including a compressor stage of an engine, and said
pressurized fluid is compressed bleed air from said compressor
stage.
3. The improvement in the aircraft according to claim 2, wherein
said slat has a plenum space therein, said wing arrangement further
includes a hot bleed air supply duct connecting said plenum space
to said aircraft bleed air system, and said pressurized fluid line
arrangement includes a bleed air line that is at least partially
arranged in said plenum space in said slat and that communicates
into said hollow space in said displacement element through said
concave rear surface.
4. The improvement in the aircraft according to claim 3, wherein
said bleed air line is regulated and connected to said aircraft
bleed air system separately and independently relative to said hot
bleed air supply duct.
5. The improvement in the aircraft according to claim 1, wherein
said improvement essentially consists of said hollow displacement
element and said pressurized fluid line arrangement, and does not
include any further movable mechanical parts.
6. The improvement in the aircraft according to claim 1, further
comprising an adhesive that adhesively surfacially bonds and
thereby secures said displacement element onto said concave rear
surface.
7. The improvement in the aircraft according to claim 1, wherein
said displacement element is expandable into an expanded
configuration of said displacement element upon inflation thereof
by introducing at least some of said pressurized fluid through said
pressurized fluid line arrangement into said at least one hollow
space, and contractible into a contracted configuration of said
displacement element upon deflation thereof by removing at least
some of said pressurized fluid from said at least one hollow
space.
8. The improvement in the aircraft according to claim 7, wherein a
sickle-shaped space is formed between said leading edge nose of
said wing body and said concave rear surface of said slat when said
slat is in said retracted slat position, said displacement element
in said contracted configuration conforms to and substantially
fills said sickle-shaped space when said slat is in said retracted
slat position, and wherein said displacement element in said
expanded configuration substantially fills a concave space bounded
by said concave rear surface of said slat when said slat is in said
extended slat position.
9. The improvement in the aircraft according to claim 8, wherein
said displacement element in said expanded configuration has such a
profile shape so as to reduce or prevent the formation of an air
vortex along said slat in said slat air gap when said slat is in
said extended slat position.
10. The improvement in the aircraft according to claim 7, wherein
said displacement element comprises an elastically stretchable
material, and is elastically stretchable into said expanded
configuration and elastically shrinkable into said contracted
configuration.
11. The improvement in the aircraft according to claim 7, wherein
said displacement element comprises a flexible material that is
form-stable to stably maintain a prescribed shape of said
displacement element in said expanded configuration.
12. The improvement in the aircraft according to claim 7, wherein
said displacement element comprises a gas-tight wall member and a
layer of abrasion resistant material arranged on at least a partial
surface area of said gas-tight wall member facing said slat air
gap.
13. The improvement in the aircraft according to claim 7, wherein
said displacement element comprises a gas-tight wall member and a
high strength woven fabric layer laminated onto an outer surface of
said wall member, and said woven fabric layer forms a stretchable
and shrinkable membrane.
14. The improvement in the aircraft according to claim 7, wherein
said displacement element comprises an outer wall member
surrounding said at least one hollow space therein, and wherein
said outer wall member has a non-uniform wall thickness that
differs at different locations so as to provide a specified outer
contour shape of said displacement element respectively in said
contracted configuration and said expanded configuration.
15. The improvement in the aircraft according to claim 7, wherein
said displacement element has a teardrop-shaped cross-sectional
shape.
16. The improvement in the aircraft according to claim 7, wherein
said displacement element has a front element surface with a front
surface contour that permanently lies along and inversely matches a
concave contour of said concave rear surface of said slat and a
rear element surface with a variable rear surface contour, wherein
said rear surface contour lies along and inversely conforms to a
convex nose contour of said leading edge nose when said
displacement element is in said contracted configuration and said
slat is in said retracted slat position, and wherein said rear
surface contour includes a convexly curved surface area bounding
said slat air gap when said slat is in said extended slat position
and said displacement element is in said expanded
configuration.
17. The improvement in the aircraft according to claim 16, wherein
said rear surface contour further includes a concavely curved
surface area adjoining said convexly curved surface area and
further bounding said slat air gap when said slat is in said
extended slat position and said displacement element is in said
expanded configuration.
18. The improvement in the aircraft according to claim 1, wherein
said at least one hollow space includes exactly one single hollow
space confined within said displacement element.
19. The improvement in the aircraft according to claim 1, wherein
said at least one hollow space includes a plurality of separated
hollow chambers, and wherein said pressure fluid line arrangement
includes a plurality of separate pressure fluid lines that are
respectively individually connected to said hollow chambers and are
adapted to independently supply said pressurized fluid into said
hollow chambers.
20. The improvement in the aircraft according to claim 19, wherein
said displacement element includes a respective separating wall
between respective adjacent ones of said hollow chambers, and a
pressure compensation valve arranged in said separating wall.
21. The improvement in the aircraft according to claim 1, wherein
said pressurized fluid line arrangement includes a pressurized
fluid line as well as a shut-off valve and a pressure regulating
valve interposed in series in said pressurized fluid line between
said source of said pressurized fluid and said, hollow space of
said displacement element.
22. The improvement in the aircraft according to claim 21, wherein
said pressurized fluid line arrangement further comprises a slat
configuration controller connected by at least one signal line to
said valves to provide control signals to said valves.
23. The improvement in the aircraft according to claim 1, further
comprising a pressure relief valve arranged in and penetrating
through a wall of said displacement element into said hollow
space.
24. The improvement in the aircraft according to claim 1, wherein
said pressurized fluid line arrangement comprises a pressurized
fluid line and a pressure relief valve connected thereto.
Description
PRIORITY CLAIM
[0001] This application is based on and claims the priority under
35 U.S.C. .sctn.119 of German Patent Application 100 19 185.1,
filed on Apr. 17, 2000, the entire disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates to a structural arrangement for
aerodynamic noise reduction in connection with leading edge slats
on the wings of commercial transport aircraft. Particularly, the
structure provides an aerodynamic effect on a wing slat in order to
reduce the noise generated by air flowing around the slat, and
through the air gap between the slat and the leading edge of the
wing, especially during take-off and landing phases of flight of an
aircraft.
BACKGROUND INFORMATION
[0003] Various noise sources contribute to the total noise
generated during the flight of a modern commercial transport
aircraft.
[0004] Among the various noise sources, aero-acoustically generated
noise that results from the flow pattern of air around the aircraft
structure is becoming an evermore significant portion of the total
flight noise. This is because the noise generated by other sources
such as the engines has been reduced in recent years by technical
advances of those components. In present day commercial transport
aircraft, it is roughly estimated that approximately 50% of the
total flight noise during a landing approach is generated by the
flow of air around the aircraft structure, while the other half of
the total noise is generated by the engines.
[0005] Further improvements, i.e. reductions, in the noise
generated by the engines are only practically and economically
efficacious if similar technical advances for reducing the
aerodynamic flow noise around the aircraft fuselage can be
simultaneously achieved. It is becoming especially important to
reduce the aerodynamic flow noise in view of ever stricter noise
level limits, especially around airports with a high aircraft
traffic volume. A major factor contributing to the total
aerodynamic flow noise during landing and take-off of a modern
commercial transport aircraft, is the noise generated by the
airflow around high-lift slats deployed from the leading edges of
the wings during the landing and take-off phases.
[0006] To facilitate an understanding of the aerodynamic noise
generated in connection with the leading edge slats, FIG. 4 of the
present application shows representative streamlines of the air A
flowing around a generally conventional wing, which is
schematically shown in section. The wing arrangement includes a
main wing 2, a leading edge slat 1 that is extended or deployed
forward of the leading edge of the main wing 2, and a landing flap
11 that is extended or deployed rearward from the trailing edge of
the main wing 2. Throughout this specification, the term forward
and the like refers to the normal forward flight direction of the
aircraft, for example the direction in which the aircraft nose and
the wing leading edges are oriented. As is generally known, the
extended slat 1 and landing flap 11 change the effective camber and
angle of attack of the airfoil profile of the wing structure, and
also influence the airflow over the surfaces of the wing, so as to
increase the lift, e.g. for landing and takeoff. In this extended
configuration, the slat 1 is deployed forwardly and downwardly from
the leading edge nose 2A of the main wing 2 so as to form a slat
air gap 13 between a rearwardly facing concave curved surface 3 of
the slat 1 and the convexly profiled leading edge nose 2A of the
main wing 2.
[0007] On the other hand, during cruise flight, the slat 1 is
retracted into a retracted position (not shown) directly on the
leading edge nose 2A of the main wing 2 so as to reduce the
aerodynamic drag and avoid unnecessary increased lift. In this
context, the leading edge slat 1 must be retracted smoothly and
flushly against the leading edge nose 2A of the main wing 2, so as
to form a substantially continuous aerodynamic contour. Namely, the
slat 1 is adjacent to the leading edge nose 2A, with at most only a
small, aerodynamically insignificant, gap or space therebetween.
Therefore, the rear concavely curved surface 3 of the leading edge
slat 1 has a profile curvature substantially matching that of the
leading edge nose 2A of the main wing 2, so that the slat 1
smoothly matches or mates onto the leading edge nose 2A of the main
wing 2 without a resistance-causing gap or discontinuity
therebetween.
[0008] Unfortunately, the profile curvature of the rear concave
surface 3 of the slat 1 may be optimal for mating onto the leading
edge nose 2A of the main wing 2 in the retracted position, but it
is not optimal for the airflow through the slat air gap 13 between
the leading edge nose 2A and the slat 1 in its deployed position as
shown in FIGS. 4. As a result, the airflow A forms an eddy or
vortex 15 that extends lengthwise along the length of the slat 1
(i.e. in the wing span direction). This vortex 15 involves the
turbulent eddy recirculation of air in the hollow space defined and
bounded by the rear concave curvature 3 of the slat 1, whereby this
space generally has a tapered concave shape or tear-drop shape.
This vortex 15 further exhibits or generates a fluctuating fluid
pressure field of the affected airflow, which is believed to be the
cause of the aerodynamic noise generated in this area. Noise
measurements in an aero-acoustic wind tunnel have confirmed that a
significant reduction of the noise generated by the extended slat
can be achieved by arranging a rigid fairing or filler member in
the space along the rear concave curvature 3 of the slat 1, which
would otherwise be occupied by the vortex 15.
[0009] Attempts have been made in the prior art to reduce the
aerodynamically generated noise, especially in connection with the
slats and the mounting thereof. For example, a study in this regard
was published by Werner Dobrzynski and Burkhard Gehlhar entitled
"Airframe Noise Studies on Wings with Deployed High-Lift Devices",
from the Deutsches Zentrum fuer Luft und Raumfahrt e.V. (DLR),
Institut fuer Entwurfsaerodynamik, Abteilung Technische Akustic,
Forschungszentrum Braunschweig, Germany, at the Fourth American
Institute of Aeronautics and Astronautics AIAA/CEAS Aeroacoustics
Conference on Jun. 2 to 4, 1998 in Toulouse, France.
[0010] Among other things, this study disclosed a proposed noise
reducing arrangement in which a sheet metal guide member is
pivotally connected to the slat in the area of the concavely curved
rear or inner surface of the slat facing toward the leading edge
nose of the main wing. This sheet metal air guide can be pivoted
relative to the slat. Particularly, the air guide member can be
extended or deployed relative to the slat during take-off and
landing when the slat is deployed relative to the wing. On the
other hand, the sheet metal air guide member will be pivoted
against the slat during cruise flight when the slat is to be
retracted relative to the wing. While such a proposed solution may
have achieved a reduction of aerodynamically generated noise in
wind tunnel tests, it is considered that such a solution could
never be practically carried out in an actual aircraft
construction, for practical reasons.
[0011] For example, in the previously proposed arrangement, when
the slat is retracted against the leading edge nose of the main
wing for cruise flight, the gap between these two components is not
sufficiently large for accommodating a rigid air guide member
tilted or pivoted inwardly against the rear surface of the slat. On
the other hand, if the gap is made larger to accommodate the air
guide member, then a disadvantageous aerodynamic gap or
discontinuity would be formed along the aerodynamic contour
provided by the slat and the wing in combination. Moreover, if a
flexible air guide component is provided, which is to be adapted
against the inner contour of the slat in the retracted position,
then such a component would not have sufficient strength and
stiffness in order to withstand the aerodynamic forces in the
deployed condition.
[0012] Moreover, such a guide element would be expected to have a
tendency to flutter due to the alternating aerodynamic pressure
effect, or simply due to a failure to remain sufficiently rigid to
withstand the aerodynamic forces. Namely, the proposed sheet metal
separating surface or air guide member will be subjected to
considerable fluctuating aerodynamic forces, which will presumably
excite vibrations or oscillations in the member, since it is only
to be pivotally connected to the lower edge of the slat without any
further stiffening means. Such fluttering generates a significant
noise radiation, which is directly contrary to the object of
reducing the noise. Furthermore, a pivotally connected sheet metal
member requires additional mechanical movable parts, which leads to
an increased total weight of the aircraft, as well as increased
manufacturing and maintenance costs. It would also be necessary to
construct the pivot joint in such a manner that the transition from
the underside of the slat to the joint of the separating surface is
free of contour discontinuities or gaps, which makes it necessary
to achieve a very high manufacturing accuracy.
[0013] Additional problems arise because the contour of the rear
surface of the slat as well as the geometry of the slat air gap
change over the span width of the wing, so that the air guide
element or elements must be configured with a bend or twist along
the length thereof, whereby the tilting and retracting mechanism
becomes further complicated.
[0014] A failure situation, for example involving a blockage of the
mechanical system of the slat arrangement, would become very
critical, because then the slat could no longer be retracted if the
air guide member is blocked or jammed in its deployed or extended
position.
[0015] The above mentioned conference proceedings provide no
suggestions toward overcoming the just mentioned significant
problems and disadvantages in actually trying to carry out the
proposed solution using a pivotable air guide member in
practice.
SUMMARY OF THE INVENTION
[0016] In view of the above, it is an object of the invention to
provide a structure for reducing the aero-acoustically generated
noise of the air flowing around a slat, which significantly reduces
the noise generation on the slat of a commercial transport
aircraft, without disadvantageously influencing the aerodynamic
characteristics such as the lift and the air resistance of the
wing.
[0017] Moreover, the structure or arrangement should be fail-safe,
so that in the event of a total or partial failure of the
arrangement, no dangerous effects that would influence the further
flight of the aircraft may arise. Furthermore, the inventive
structural arrangement shall entirely avoid the use of movable
mechanical elements and elements that significantly increase the
total weight of the aircraft. The inventive structural arrangement
shall also be easily installable or even retrofittable into
existing aircraft, and have a simple and minimal maintenance
requirement. The invention further aims to avoid or overcome the
disadvantages of the prior art, and to achieve additional
advantages, as apparent from the present specification.
[0018] The above objects have been achieved according to the
invention in an aircraft wing arrangement including a main wing and
a slat that is movably connected to the main wing so as to be
movable between an extended position in which the slat extends
forwardly of the leading edge nose of the wing and a retracted
position in which the slat is arranged adjacent to the leading edge
nose. Particularly according to the invention, the aircraft wing
arrangement includes an improved structure for reducing
aero-acoustically generated noise, comprising a displacement
element (which is especially and preferably an expandable
displacement element such as a hollow bellows or inflatable elastic
displacement element) that is arranged on the concavely curved rear
surface of the slat that faces toward the leading edge nose of the
main wing. The inventive improvement further comprises a pressure
conduit such as a bleed air line that communicates with a hollow
space in the displacement element so as to selectively expand or
contract the displacement element. The terms "conduit", "line",
etc. refer generally to any duct, hose, pipe, tube, channel,
conduit or the like through which a fluid may be conveyed. Any
available pressurized fluid and preferably pressurized air can be
used to selectively expand the displacement element. Preferably,
compressed bleed air from the engine or engines of the aircraft is
controlledly supplied into the expandable displacement element.
[0019] When the displacement element is completely contracted, it
is rather thin and contracted against the concave rear surface of
the slat, so that it can be accommodated in the crescent-shaped or
sickle-shaped space (referring to the cross-sectional shape)
between the slat and the leading edge nose of the main wing when
the slat is fully retracted. On the other hand, when the
displacement element is fully expanded, it preferably has a
substantially teardrop shaped cross-section, which protrudes
rearwardly from the concavely curved rear surface of the slat and
forms a protruding convexly curved surface of the displacement
element that faces the leading edge nose of the main wing. Thus,
when the slat is in the extended position, the slat air gap between
the slat and the leading edge nose of the main wing is bounded
between the convexly curved rear surface of the expandable
displacement element and the aerodynamically convexly curved
profile contour of the leading edge nose. The rear surface of the
expandable displacement element may further have a compound
curvature including convex and concave portions, to optimize the
flow configuration of the slat air gap.
[0020] The inventive improved structure achieves several
advantages. The expandable displacement element improves or even
optimizes the flow configuration of the slat air gap, so that the
aerodynamic effectiveness of the slat can be improved, and
especially so that the formation of a vortex on the rear surface of
the slat is avoided, thereby significantly reducing the
aero-acoustic generation of noise from the slat. On the other hand,
when the expandable displacement element is deflated and thus
contracted, it is rather thin and conformable to the concavely
curved contour of the rear surface of the slat, so that it can be
compactly accommodated between the slat and the leading edge nose
of the wing when the slat is in the fully retracted position. In
this configuration, the displacement element flexibly deformably
adapts to the available space between the retracted slat and the
leading edge nose of the wing and thus advantageously fills any gap
remaining between the slat and the wing. The structure is
economical and simple to fabricate and to install, and may even be
easily retrofitted onto existing aircraft. The added weight is
quite low. The arrangement provides a fail-safe operation, whereby
even a complete failure of the arrangement will not hinder the
normal retraction or extension of the slat relative to the
wing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order that the invention may be clearly understood, it
will now be described in connection with example embodiments, with
reference to the accompanying drawings, wherein:
[0022] FIG. 1 is a schematic cross-sectional view of a slat in a
retracted position relative to a main wing, with an expandable
displacement element arranged on a rear surface of the slat being
in a contracted or deflated condition;
[0023] FIG. 1A is an enlarged detail view of a portion of FIG. 1,
especially showing a bleed air line supplying bleed air into the
expandable displacement element;
[0024] FIG. 2 is a schematic sectional view of the arrangement of
FIG. 1, but with the slat in an extended position and the
displacement element in an expanded condition;
[0025] FIG. 3 is a schematic cross-sectional view similar to FIG.
2, but showing an alternative embodiment with a multi-chambered
expandable displacement element rather than a single-chambered
displacement element; and
[0026] FIG. 4 is a schematic cross-sectional view of a conventional
wing arrangement showing the air streamlines that prevail when a
slat and a landing flap are extended.
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE
BEST MODE OF THE INVENTION
[0027] The general structure of a main wing 2 with an extended
high-lift slat 1 and an extended landing flap 11, as well as the
aerodynamic flow streamlines A associated therewith, in a
conventional arrangement, have been discussed above in connection
with FIG. 4. The point of the invention is especially to avoid or
reduce the formation of the vortex 15 along the slat 1 while
improving the aerodynamic configuration of the slat air gap 13 when
the slat 1 is in the extended position, while still allowing a
proper full retraction of the slat 1 against the leading edge nose
2A of the main wing 2. The inventive arrangement shall not have
disadvantageous influences on the aerodynamic characteristics, such
as the lift and the aerodynamic resistance, but rather actually
improves these aerodynamic characteristics.
[0028] The inventive structural arrangement will now be described
in connection with FIGS. 1 to 3. The key components of the
inventive structural arrangement are a hollow displacement element
4, and a pressurized fluid line such as a bleed air line 20 that
provides compressed bleed air selectively into the hollow
displacement element.
[0029] The displacement element 4 is particularly expandable and is
arranged and secured on the concavely curved rear facing surface 3
of the slat 1. Preferably, the displacement element 4 is a hollow
body that is inflatable so as to be selectively blown-up or
expanded by a pressure medium selectively introduced therein from
the pressure medium line, e.g. the bleed air line 20, as will be
described in greater detail below. In the illustrated embodiment,
the displacement element 4 is an inflatable, elastically expandable
hollow bag or bellows element comprising an elastically stretchable
material that is substantially gas-tight. Alternatively, the
material of the displacement element 4 need not be elastically
stretchable, but instead may merely be flexibly deformable so as to
be inflatable to an expanded inflated condition and contractible to
a deflated or contracted condition, without stretching and
shrinking.
[0030] Preferably, the displacement element 4 extends
longitudinally along the entire length of the slat 1 in the span
direction, and extends vertically along or covers the entire
concavely curved rear surface 3 of the slat 1 facing toward the
leading edge nose 2A of the wing 2. The displacement element 4 may
be secured to the slat 1 by any conventionally known means, but
preferably is adhesively bonded in a fully surfacial manner to the
entire concave contoured rear surface 3 of the slat 1 using any
suitable adhesive. Thereby, the expandable displacement element 4
does not require any additional mechanical supports, guide members,
mountings, or actuators for securing the displacement element 4 to
the slat 1, or for selectively deploying the displacement element 4
between its expanded condition and its contracted condition.
[0031] Instead, the displacement element 4 is simply constructed
and adapted to be two- or three-dimensionally expandable into the
appropriately contoured expanded shape as shown in FIG. 2, and to
be contractible into the contracted shape shown in FIG. 1. To
achieve this, the material of the element 4 is preferably
form-stable to maintain the desired specified configuration,
especially in the expanded condition. This may be achieved, for
example, with an appropriately layered or composite material, for
example including a shape-retaining mesh or woven fabric bag in
combination with a gas-tight membrane layer. Also, the wall
thickness of the walls of the displacement element 4 is
appropriately dimensioned, and may be non-uniform with different
wall thicknesses in different areas, in order to provide the
appropriate shape respectively when the displacement element 4 is
in the contracted condition as shown in FIG. 1 and/or in the
expanded condition as shown in FIG. 2.
[0032] Preferably, at least the outer rear surface 17 of the
displacement element 4 facing away from the slat 1 and generally
toward the wing 2 further includes an outer layer of an abrasion
resistant material to provide protection against mechanical damage
as well as attack by aggressive agents such as environmental
pollutants, possible exhaust gases, spilled fuel, hydraulic oil, or
the like, and generally to increase the durability, wear
resistance, and operating life of the displacement element 4, with
a low maintenance and upkeep requirement. For example, a high
strength and abrasion resistant woven fabric can be laminated onto
the wall material of the displacement element 4 on the rear surface
17 thereof. This layer can further provide the expanding and
shrinking function of an elastic membrane while defining the
contour shape of the element 4. Moreover, this membrane constrains
and protects the displacement element 4 against bursting in the
event of over-pressurization thereof. In any event, the material or
materials, the geometry, and the pressurization of the displacement
element 4 are selected in such a manner that the inflated element 4
will be form-stable and maintain the proper contour shape without
fluttering even in the event of pressure fluctuations of the air
flowing through the slat air gap 13.
[0033] As mentioned above, a pressure medium, and preferably
compressed engine bleed air, is selectively provided into the
hollow space of the displacement element 4 so as to selectively
contract the element into the contracted condition shown in FIG. 1,
or to expand the element into the expanded condition shown in FIG.
2, or to adjustably partially expand the element 4 to any
intermediate condition to achieve the required contour shape
thereof to optimize the aerodynamic flow conditions through the
slat air gap 13 under different flight conditions or
configurations. To achieve this, any suitable bleed air line is
connected from the bleed air system of the aircraft into a hollow
space 7 within the expandable displacement element 4.
[0034] As shown in FIGS. 1 and 2, a telescoping tube 9 is connected
between the slat 1 and the wing 2, and may movably or extendably
mount the wing 1 on the wing 2. This telescoping tube 9
additionally conveys hot engine bleed air through an air duct 18
into an air plenum space 5 within the hollow interior of the slat
1. This portion of hot bleed air heats the slat 1 and may then be
exhausted out of an exhaust blowing opening 19, both for the
purpose of de-icing, for example. Another portion of engine bleed
air can be separately conveyed, for example through a separate air
line extending in the telescoping tube 9, to a bleed air line 20
that extends longitudinally at least discontinuously or
section-wise in the hollow plenum space 5 within the slat 1, and
from there penetrates through the rear surface 3 of the slat 1 and
through the adjoining wall of the displacement element 4, to
communicate into the hollow space 7 within the element 4, as shown
in detail in FIG. 1A. In this manner, a bleed air supply with
appropriate control and pressure regulation is provided for
selectively inflating or contracting the displacement element 4,
completely separately from the hot bleed air supply that is blown
into the plenum space 5 of the slat 1 for the purpose of
de-icing.
[0035] The pressurized fluid may be provided from any pressurized
fluid source in the aircraft, but is preferably engine bleed air
from the aircraft bleed air system, which taps compressed bleed air
from the compressor stages of the main engines and/or an auxiliary
power unit engine of the aircraft. Then, from the bleed air system,
the compressed bleed air is delivered through at least one shut-off
valve or control valve 25 and at least one pressure regulating
valve 26 in series to the bleed air line 20 that communicates into
the hollow space 7 of the displacement element 4. The valve
arrangement is connected for control signal reception from a slat
contour regulating or controlling unit 27, which provides control
signals for controlling the valve or valves. Thereby, the inflation
and deflation of the displacement element 4 is selectively
controlled as will be described below. These valves can be located
at any point between the bleed air system of the aircraft and the
outlet of the bleed air line 20 into the displacement element 4. It
should be noted that at least the portion of the bleed air line 20
extending through the telescopable tube 9 may be a flexible hose or
compensating pipe connection in order to allow an adaptable
movability of the components, and particularly the slat 1 relative
to the wing 2.
[0036] It should be clear that the compressed bleed air provided
through the control valves to the bleed air line 20 and into the
hollow space 7 of the displacement element 4 selectively inflates
the displacement element 4 to the required inflated or partially
inflated condition. On the other hand, there must also be provision
for deflating the displacement element 4. This can be achieved by
closing the supply shut-off valve 25 while allowing air to vent out
of the pressure regulating valve 26 located serially downstream
from the control valve. In this state, if the displacement element
4 is mechanically squeezed between the slat 1 and the wing 2 as the
slat is being retracted, then the air will be squeezed out of the
displacement element 4 and allowed to escape through the pressure
regulating valve 26.
[0037] Alternatively, the displacement element 4 can be actively
deflated and contracted by actively sucking air back out through
the bleed air supply line 20, through a suitable connection to any
available suction source in the aircraft. As a further alternative,
a controlled or passive venting valve or pressure regulating valve
23 may be provided directly through the wall of the displacement
element 4. Thereby, air can be vented out of the hollow space 7 in
the event of an over-pressure inflation of the displacement element
4, or to achieve the normal collapsing of the element 4 into the
contracted condition due to a squeezing force applied thereto by
the slat 1 and the leading edge nose 2A of the wing 2 as the slat 1
is retracted (or due to the elastic shrinking of the element 4
itself), or in the event of a failure of the pressurization system,
whereby the element 4 can be contracted even from a fully inflated
and pressurized condition, when the slat 1 is retracted and thereby
squeezes the element 4 between the slat 1 and the wing 2.
[0038] While FIG. 2 shows a simple single-chamber embodiment of a
displacement element 4 having a single hollow space 7 therein, FIG.
3 shows an alternative of a multi-chambered displacement element 4,
which has, for example, three hollow chambers 8 separated from each
other in the overall hollow space 7. Preferably, the three hollow
chambers 8 each respectively receive separately controlled or
regulated supplies of pressurized bleed air through respective
branches of the bleed air line 20 from the bleed air system of the
aircraft. By separately controlling the supply of pressurized air
into the three separate spaces or chambers 8, the particular
sectional shape of the displacement element 4 can be controlled
with greater precision.
[0039] While the expanded displacement element 4 of FIG. 2 has a
general tear-drop shape defined by the material and shape of the
displacement element 4 and by its pressurization condition, the
three-chambered displacement element 4 of FIG. 3 may have a more
complex shape, for example including a better-defined complex
curvature including a convex curvature portion 17A and a concave
curvature portion 17B on the rear surface 17 of the displacement
element 4. Thereby, the aerodynamic flow conditions through the
slat air gap 13 can be optimized for different flight conditions.
Each of the chambers of this displacement element may individually
be provided with a respective venting valve or pressure relief
valve like the valve 23 described above. Also, a pressure
compensating valve 24 may be provided in each of the dividing walls
between the respective chambers 8.
[0040] Now, the operation of the inventive system or structural
arrangement will be described in connection with FIGS. 1 to 3. FIG.
1 shows the state with the slat 1 retracted adjacent to the leading
edge nose of the wing 2, which is generally the cruise flight
configuration. In this configuration, the displacement element 4
has been deflated so that it can be accommodated in the small
sickle-shaped gap between the rear surface 3 of the slat 1 and the
leading edge nose 2A of the wing 2, while flexibly conforming to
these two bounding surfaces and adaptively substantially filling
out the gap space therebetween (for example filling at least 90% of
the available gap space). The hollow space 7 within the
displacement element 4 preferably contains some air in this state,
to ensure that the element 4 still adaptively fills out the
available space. In this state, however, the remaining air in the
hollow space 7 is not under considerable pressure. Instead, the
pressurized air has either been actively sucked out of the element
4 or allowed to passively escape in any of the manners described
above.
[0041] For example, when the slat 1 is about to be retracted from
the extended position shown in FIG. 2, the shut-off valve 25 and
pressure regulating valve 26 are appropriately controlled to vent
the pressurized air out of the element 4, for example under the
influence of the elastic contraction of the element 4, and/or under
the collapsing effect of the element 4 being squeezed between the
slat 1 and the wing 2 as the slat is retracted.
[0042] Also note that the wall thickness of the element 4 can be
non-uniform to help ensure the proper cross-sectional profile of
the element 4 in the retracted state as shown in FIG. 1.
[0043] Then, when the slat 1 is extended into the position shown in
FIG. 2, appropriate control signals are provided to the shut-off
valve 25 and pressure regulating valve 26 so as to inflate the
single chamber or multiple chambers 7, 8 of the displacement
element 4 to achieve the desired inflated condition as shown in
FIGS. 2 or 3. In this condition, the displacement element 4 fills
out the concave space of the rear surface 3 of the slat 1 and
improves the flow configuration through the slat air gap 13 so as
to prevent or reduce the formation of a vortex 15 at the location
of the displacement element 4. This configuration is generally
applicable during take-off and landing of the aircraft. The exact
degree of inflation of the element 4 can be adjusted, depending on
the particular conditions. Then, when the slat 1 is again to be
retracted, the displacement element 4 must simply be depressurized
again as described above, so that the element 4 will contract or be
collapsed so as to adaptively be accommodated in the remaining
space between the retracted slat 1 and the leading edge nose 2A of
the wing 2.
[0044] A complete system according to the invention may include a
plurality of displacement members 4 respectively arranged on
separate slat members of the aircraft wing, whereby each of the
displacement elements 4 generally is constructed and operates as
described above. However, the plural displacement elements 4 may
respectively have different dimensions, different configurations,
different air volume capacities, and different expansion
characteristics, in order to achieve different displacement element
geometries of the respective plural elements 4, at different
locations or portions of the aircraft wing. Such different
properties may be required, for example, in connection with an
outboard slat in comparison to an inboard slat, for example due to
the tapering configuration of the aircraft wing and different
aerodynamic conditions at different locations.
[0045] The inventive arrangement completely avoids additional
mechanical positive guide mechanisms or positioning mechanisms, and
instead can entirely consist of an inflatable bag-like or tube-like
displacement element 4 adhesively bonded onto the rear surface of
the slat 1, and connected by a bleed air line 20 to the bleed air
system of the aircraft. This provides an especially simple system,
with very low cost, weight and maintenance, and also very low risk
of failure or malfunction. Moreover, even in the event of a partial
or complete failure of the system, the inventive system would not
cause any interference to the normal operation of the slat. Namely,
even if the slat is retracted while the displacement element 4 is
fully inflated, the pressure relief valves will ensure that the
pressurized air will be vented out of the displacement element and
that the displacement element can be collapsed between the slat and
the wing as the slat is retracted.
[0046] Although the invention has been described with reference to
specific example embodiments, it will be appreciated that it is
intended to cover all modifications and equivalents within the
scope of the appended claims. It should also be understood that the
present disclosure includes all possible combinations of any
individual features recited in any of the appended claims.
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