Note: Descriptions are shown in the official language in which they were submitted.
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LIFT AUGMENTATION SYSTEM
BACKGROUND OF THE INVENTION
Broadly, this invention concerns a system for increasing the design lift
capability of an airframe either as optional new equipment or as a retrofit.
More
particularly, the invention involves a system providing additional lift
capability on
demand through use of lightweight flexible sheet materials.
SUMMARY OF THE INVENTION
A lift augmentation system according to the present invention may include a
leading edge support that is extendable. Such extendability may permit the
lift
augmentation system to telescope longitudinally along an existing wing. That
extendablity may also permit the lift augmentation system to rotate between a
stowed position and a deployed position. The lift augmentation system also
includes
at least a pair of flexible surface elements carried in part by the leading
edge support
and which function as aerodynamic surfaces for the lift augmentation system.
One
of those flexible surface elements at least partially defines the suction
surface for the
lift augmentation system. Another of those flexible surface elements at least
partially defines the pressure surface for the lift augmentation. system. To
change
the lift augmentation area, a deployment system for the lift augmentation
system is
operable to extend and retract the leading edge support as well as the
flexible surface
elements.
The flexible surface elements may be fabricated from one or more materials.
Suitable materials include, for example, fabric-based materials, composite
materials,
carbon fiber reinforced materials, synthetic polymer sheet materials, woven
cloth
materials, and materials having laminated surface layers. In some
applications,
battens may be used to locally stiffen the flexible surface elements.
The deployment system may include a spar subsystem for extending and
retracting the leading edge support and a fabric control subsystem for
deployment
and retraction of the flexible surface elements. Suitable fabric control
subsystems
may include a roller on which the flexible surface elements are wrapped. A
suitable
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conventional motor may control the deployment of the flexible surface elements
as
the lift augmentation system is extended and recover the flexible surface
elements as
the lift augmentation system is retracted. Where multiple flexible surface
elements
are used for the lift augmentation system, multiple rollers may advantageously
be
used. To secure the flexible surface elements to structural elements of the
lift
augmentation system, slide systems may be provided on structural members where
the slide systems slidably receive corresponding edges of the flexible .
surface
elements. In some applications, a cable and pulley system may be used for the
fabric deployment subsystem.
Suitable spar deployment subsystems may include various mechanical
arrangements. For example, one or more rack and pinion arrangements may be
provided with the rack element attached to a spar and the pinion drive
attached to a
stationary support. Alternatively, a screw-drive system may be used. In a
screw
drive system, a rotatable threaded member may be attached to a spar while a
fixed
cooperating element is secured to a stationary support. Or, a fixed threaded
member
carried by a spar may cooperate with a rotatable cooperating element rotatably
carried by the stationary support. Regardless of the mechanical arrangement,
the
spar deployment subsystem is preferably operable to move the leading edge
support
between first and second positions, where the first position may be a fully
stowed or
retracted position and the second position may be a fully extended or
partially
extended position. Where the lift augmentation system is positioned at the tip
of an
existing aerodynamic surface, the spar deployment subsystem may telescopically
move the spar. Where the lift augmentation system comprises a pivotal system,
the
first position is typically fully stowed while the second position is
typically fully
deployed.
The lift augmentation system of this invention can be used as a subassembly
for original equipment, or as a subassembly for retrofit applications. In
either event
it can be used with a multiplicity of airframes. Preferably, when used in a
wing-tip
augmentation scenario, the lift augmentation system increases the nominal wing
area
in the range of about 15% to about 35%. In the wing-tip augmentation
application,
the lift augmentation system has a cross-sectional configuration that
corresponds to
the cross-sectional configuration of the existing wing tip. Furthermore, the
leading
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edge element preferably has a contour conforming to the contour of the
existing
leading edge so that as the lift augmentation system is deployed and
retracted, the
leading edge element slidably moves longitudinally with respect to the leading
edge
of the wing without deleteriously affecting aerodynamics of the existing wing.
As desired, the airframe may be manned or unmanned and remotely
controlled. Furthermore, the airframe may include any of a variety of
propulsion
systems including, by way of example, a jet engine, pusher type propellers,
pull type
propellers, diesel engine, rotary engine, ducted fan engine, a mixed cycle
engine, or
a mixed combination such as a forward-mounted fuel-burning reciprocating
engine
in conjunction with an aft-mounted small jet or gas turbine engine.
BRIEF DESCRIPTION OF THE DRAWINGS
Many objects and advantages of the present invention will be apparent to
those skilled in the art when this description is read in conjunction with the
attached
drawings wherein like reference numerals have been applied to like elements
and
wherein:
FIG. 1 is a schematic perspective view of an airframe having a lift
augmentation system according to the present invention;
FIG. 2 is a top view of the lift augmentation system in a fully deployed
position;
FIG. 3 is a front view of the lift augmentation system in a fully deployed
position;
FIG. 4 is a top view in partial cross section of the lift augmentation system
in
a fully deployed position;
FIG. 5 is an enlarged partial cross-sectional view taken along the line 5-5 of
FIG. 4;
FIG. 6 is an enlarged partial cross-sectional view taken along the line 6-6 of
FIG. 4;
FIG. 7 is an enlarged partial cross-sectional view taken along the line 7-7 of
FIG.4;
FIG. 8 is an enlarged partial cross-sectional view taken along the line 8-8 of
FIG. 4;
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FIG. 9 is a schematic top view of a lift augmentation system arranged for
pivotal deployment;
FIG. 10 is a view in partial cross section taken along the line 10-10 of FIG.
9;
FIG. 11 is a view in partial cross section taken along the line 11-11 of FIG.
9;
FIG. 12 is a view similar to FIG. 9 showing stowed and deployed positions
for the leading edge spar;
FIG. 13 is a schematic top view of a lift augmentation system having a pair
of wing assemblies;
FIG. 14 is a schematic front view of the embodiment of FIG. 13; and
FIG. 15 is a schematic perspective view of a lift augmentation system
mounted for use on an unmanned, unpowered airframe.
DETAILED DESCRIPTION OF THE INVENTION
For purposes of this description, the term airframe is intended to be a
generic
reference to any type of vehicle that can move through a gaseous medium such
as
air. For example, airframe includes, by way of example and without limitation,
airplanes, gliders, lifting bodies, spacecraft during recovery, helicopters,
and the
like. The airframe may be powered by a propulsion system, or it may be
unpowered. Similarly the airframe may be manned, or unmanned, or remotely
controlled.
Turning to FIG. 1, an airframe comprising a suitable conventional airplane
20 includes a high wing assembly 22 attached to and supported by a fuselage
24.
The wing assembly 22 typically has left and right wings, 22a, 22b. Each wing
normally is designed to have a nominal wing area. As depicted, the airplane 20
also
has a twin-boom tail assembly 26 attached to and supported by the high wing
22.
To provide powered flight, the airplane 20 also includes a pair of propulsion
units 28, 30. Each propulsion unit 28, 30 may operate on any suitable
conventional
fuel, including without limitation, gasoline, diesel, and synthetic fuels.
Moreover,
each propulsion unit may operate on any desired thermodynamic cycle.
Furthermore, each propulsion unit may comprise an internal combustion engine,
a
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jet engine, a rotary engine, a mixed cycle engine, or a ducted fan engine.
Each
propulsion unit may be operably connected to a propeller, or other suitable
device
for driving the airframe through air. Here, for example, a forward mounted
propeller 32 is driven by one of the propulsion units 28, while a ducted fan
34
positioned between the twin booms of the tail assembly 26 is driven by the
other one
of the propulsion units 30. The propulsion units 28, 30 can operate
simultaneously
or one at a time. Thus, the ducted fan 34 functions as a pusher-type propeller
and
could be positioned at the back of the fuselage 24 to attain quieter operation
than
would occur with a front-mounted pull-type propeller 32.
The outboard end of each wing 22a, 22b includes an extendable/retractable
wing-tip lift augmentation assembly 40. The wing-tip lift augmentation
assemblies
40 are mirror images of one another. Accordingly, it will suffice to describe
one of
the assemblies 40 as it will be understood that the other has the same
features but
operates in a reflected way. Each wing tip assembly 40 can be essentially self
contained. As a result, the wing tip assemblies 40 may be offered as a
retrofit
accessory for an existing aircraft. Alternatively, the wing tip assemblies 40
may be
offered by original equipment manufacturers as optional equipment.
Each wing-tip assembly 40 is movable between a first, fully retracted
position 40' (shown in phantom lines in FIG. 2) and a second position (shown
in
solid lines in FIG. 2). The second position may be the fully extended position
depicted in FIG. 1 or an intermediate position located between the fully
extended
and fully retracted positions. In this way, as the wing-tip assembly 40 is
extended,
the area of the associated wing 22a, 22b is increased and the available lift
for the
airplane 20 increases. A wing-tip assembly 40 may increase the nominal area of
the
associated wing by as much as about 100%. Preferably, the area increase will
be
about 50% and most preferably the area increase will be in the range of about
15%
to about 35%. Moreover, the wing-tip assembly increases the aspect ratio for
the
combined original wing and assembly 40, thereby increasing the lift and
aerodynamic efficiency of the resulting combination.
While the chord of the wings 22a, 22b in FIG. 1 is shown as a constant, the
wing-tip assembly 40 can be used with wings that taper in the direction from
the
fuselage to the wing tip. Regardless of whether the wing is tapered or not,
the
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leading edge of the wing-tip assembly should be essentially collinear with the
leading edge of the associated wing. Moreover, the trailing edge of the wing-
tip
assembly 40 should be essentially parallel to its leading edge, with the chord
of the
wing-tip assembly 40 being substantially the same length as the chord of the
associated wing tip.
To further enhance the lift augmentation properties of the wing-tip assembly
40, it may be provided with an upwardly extending fence 42, as well as a
downwardly extending fence 44. As desired, the fences 42 on opposite wing tips
may have a dihedral angle between them. Likewise, the fences 44 on opposite
wing
tips may also have a dihedral angle therebetween. These wing-tip fences 42, 44
are
effective to reduce the secondary air circulation flow between the bottom or
pressure
surface of the wing and the top or suction surface of the wing. Reduction of
that
three-dimensional secondary flow also enhances the lift otherwise available
from the
wing 22. As will be described more fully below, these wing-tip fences 42, 44
may
also function as fairings to conceal apparatus related to extension and
retraction of
the lift augmentation system 40.
Turning now to FIG. 2, the wing-tip lift augmentation assembly 40 includes
an extendable leading edge support 50 having a length which exceeds the
spacing
between the retracted position 40' and the extended position. In this way, the
leading edge support 50 can provide additional cantilever support for the lift
augmentation system. Preferably the leading edge support 50 includes an edge
cuff
52 which may be fabricated from a carbon-fiber-reinforced epoxy matrix or
other
equivalent material, including laminates. The edge cuff 52 conforms to the
leading
edge contour of the associated wing 22b and has a length sufficient to give
continuity to the leading edge when the lift augmentation system assembly 40
is
fully extended. To support the edge cuff 52 and reduce forces resisting its
sliding
movement, suitably shaped polytetrafluroethylene (Teflon~) pads (not shown),
or
other suitable material with similar characteristics, may be provided between
the
leading edge cuff 52 and the upper and lower surfaces of the wing leading
edge.
The pads can be applied to either the inside of the leading edge cuff 52 or to
the
external surfaced of the wing. Preferably, the pads are applied to the inside
surfaces
of the edge cuff 52 to reduce potential disruption of airflow over the wing in
normal
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operation. Those pads also permit the cuff 52 design to support some torsion
and
bending loads which are applied to the associated wing 22b when the lift
augmentation system is deployed.
The lift augmentation system 40 also includes at least two flexible surface
elements, one surface element 54 is located on the top or suction surface of
the lift
augmentation system while one other surface element is located on the bottom
or
pressure surface of the lift augmentation system . Moreover, it is
contemplated that
two or more surface elements 54, 56 may be used for the suction surface, as
well as
for the pressure surface of the lift augmentation system 40.
The flexible surface elements are preferably fabricated from sheet material
that is sufficiently flexible that it can be rolled. The material may be woven
or non-
woven. The flexible surface elements may also be fabricated from any suitable
conventional dimensionally stable synthetic material such as aramid fiber
(e.g.,
Kevlar~), polyester fiber (e.g., Dacron~), ultra high molecular weight
polyethylene
fibers (e.g., SpectraTM), high strength liquid crystal polymer fiber (e.g.,
VectranTM),
nylon, or the like. Furthermore, the material of. the flexible surface
elements is
selected such that it is sufficiently strong that it can withstand, without
failure,
aerodynamic pressures and forces to which the lift augmentation system will be
subjected during flight operations. Material having carbon fiber reinforcement
is
also suitable for these flexible surface elements. Such carbon fiber
reinforcement
may be used as a component of a fabric-based material. The material may
comprise
a film of synthetic polymer sheet material, or a composite material. For
example, a
composite material may comprise a cloth woven with aramid, polyester, and/or
carbon fibers and including laminated surface layers such as a polyester film
(e.g.,
Mylar~) for strength and stretch resistance and an outer layer of PVF film
(e.g.,
Tedlar) or PVDR (e.g., Kynar) for ultraviolet protection.
A deployment system is provided to extend and retract the lift augmentation
system relative to the wing tip and to extend and retract the flexible surface
elements, thereby changing the augmentation area. The deployment system
includes
a spar subsystem for extending and retracting one or more spars and a fabric
control
subsystem for deploying and retracting flexible surface elements.
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To support the lift augmentation system 40 relative to the wing or airframe, a
leading edge spar 60 (see FIG. 4) may be attached to a bulkhead 62 at the tip
of a
wing. Preferably , the leading edge spar 60 is mounted so that is can move
longitudinally with respect to itself as the lift augmentation system 40 moves
between its first and second positions. To provide the required structural
support,
the leading edge spar 60 may also be supported by other structures in the
existing
wing. A mid-chord spar 64 may also be provided for support of the lift
augmentation system. The mid-chord spar 64 would also be longitudinally
slidable
with respect to itself as the lift augmentation system 40 moves between its
first and
second positions. A suitable conventional actuator 66, such as a DC motor, may
be
provided for at least one of the spars 62, 64. Preferably an actuator 66 is
provided
for each spar to reduce binding during deployment and retraction.
Mechanically, the lift force exerted on the wing tip assembly may be reacted
by the suitable conventional frictionless bearings (not shown) that guide the
associated spars 60, 74 during extension and retraction. The outboard bearing
generates a downwardly directed reaction force while the inboard bearing
generates
an upwardly directed reaction force, the bearing reaction forces generating a
force
couple that reacts at least part of the moment exerted by the lift force on
the end of
the corresponding wing 22.
One end of each flexible surface element 54, 56 is attached to the bulkhead
62 to secure it and provide a substantially continuous aerodynamic surface for
the
associated wing. The other end of each flexible surface element 54, 56 is
preferably
attached to a fabric control subsystem for regulating the deployment and/or
retraction of the flexible surface elements. The fabric control subsystem may
include, for example, one or more corresponding rollers carried at the end of
the lift
augmentation system within the fairings provided by the lift enhancement
devices
42, 44. The flexible surface element collection/deployment rollers may be
carried
on a single shaft and operated by a suitable conventional actuator 68, such as
a DC
motor, which is also located within the fairings provided by the lift
enhancement
devices 42, 44. For example, the actuator 68 may include a gear (see FIG. 5)
which
meshes with a gear 70 at the end of the roller shaft. Thus, as the actuator 68
operates, it can control the rate at which the flexible surface elements 54,
56 are
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deployed or retracted. Moreover, the actuator 68 provides a mechanical detent
to
rotationally fix the collection/deployment rollers so that the quantity of the
flexible
surface deployed can be controlled. The roller assembly (see FIG. 4) carried
at the
outboard end of the wing tip assembly 40 furls and deploys the flexible
surface
material. More particularly, the flexible surface element 56 (see FIG. 7) may
be
furled on a forward roller assembly 72 and the aft surface element 56 may be
furled
on a corresponding aft roller assembly (not shown). To simplify operation, the
upper surface element 54 may be positioned above a corresponding lower surface
element 54'. The upper and lower surface elements 54, 54' are simultaneously
deployed and furled from the roller assembly 72 by wrapping them
simultaneously
around the roller assembly 72 during furling and by simultaneously paying them
out
from the roller assembly 72 during deployment.
Various actuating mechanisms may be contemplated for the spar deployment
subsystem to deploy the wing-tip lift augmentation system assembly 40 relative
to
an existing wing. For example, one suitable actuating mechanism may include a
suitable conventional gear rack 70 (see FIG. 6) attached to or integral with
the
leading edge spar 60. The gear rack 70 cooperates with a corresponding
actuator 66
(see FIG. 4) to extend and retract the assembly 40 relative to the wing by
longitudinally translating the leading edge spar 60. Another suitable
mechanism
would be a rotary screw and conforming threaded collar. Here, the screw may be
attached to either the leading edge spar or the existing wing structure and
the
conforming collar may be attached to the other of the leading edge spar or the
existing wing structure. Either the screw or to conforming collar may be
rotated to
advance and retract the leading edge spar relative to the existing wing.
. While the accompanying figure depict the leading edge spar as a single
element, it is contemplated that the leading edge spar may also be a sectional
system
where shorter sections telescopically are received by other sections so that
the
overall length of the leading edge spar can be reduced. In such an
arrangement, the
spar deployment subsystem can telescopically move the leading edge between
first
and second positions as described. Furthermore, the leading edge spar may be
telescopically received in a conforming sleeve which can be mounted to an
existing
aircraft structure to simplify retrofit applications.
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To facilitate proper tracking of the surface elements during retraction and
deployment, each flexible surface element may include fore and aft
protrusions, e.g.,
80, 82 (see FIGs. 6 and 8), that are received in correspondingly shaped
channels e.g.,
84, 86, provided in the front and mid-chord spars 60, 64, respectively. More
particularly, the upper flexible surface element 54 has a protrusion 80 (see
FIG. 6)
supported close to the upper edge of the leading edge spar 60 and another
protrusion
82 (see FIG. 8) supported close to the upper edge of the spar 64. Similarly,
the
lower flexible surface element has a protrusion 80' (see FIG. 6) supported
close to
the bottom edge of the leading edge spar 60 and another protrusion 82'
supported
close to the bottom edge of the spar 64. The other flexible surface elements
56, 56'
have a protrusion 83, 83', respectively, at the forward edge (in the direction
of
airflow over the lift augmentation system) but not at the rear edge. The
protrusion
83 of the upper flexible surface element 56 is located at the upper edge of
the spar
64 while the protrusion 83' of the flexible surface element 56' is located at
the lower
edge of the spar 64. The rear edges (see FIG. 4) of the aft flexible surface
elements
56, 56' are connected to hold them together during use. In some applications,
it may
also be desirable to shape those rear edges by providing a concave curvature
facing
the downstream direction for flutter control or compensation.
Those protrusions 80, 80', 82, 82', 83, 83' and the associated channels are
analogous to the bolt rope used in sails and the corresponding spar channels
provided to receive them. As seen in FIG. 7, the end portion 90, 90' of each
channel 84, 84' may be faired or smoothed to provide a gradual entry for the
edge of
the flexible member thereby reducing the likelihood of damage to the flexible
members 54, 54' from sharp edges. With this arrangement the flexible surface
elements can be securely carried by at least one spar in such a way that
smooth
airflow over the spar-surface element interface is maintained.
Another embodiment of the lift augmentation system according to this
specification is depicted in FIG. 9. In this embodiment, the deployment system
includes a spar deployment subsystem that pivotally extends and retracts the
leading
edge spar while the fabric control subsystem extends and retracts flexible
surface
elements along the leading edge spar. For example, in this embodiment, the
lift
augmentation system 40 includes an extendable leading edge spar that can be
moved
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about a vertical axis through a pivot 100 in a plane. The extendable leading
edge
spar 102 is positioned at the forward edge of the lift augmentation system 40.
A
wing-tip assembly 104 may be pivotally connected to the outboard end of the
leading edge spar 102 and defines the outboard end of the lift augmentation
system
40.
To provide lift augmentation, a flexible surface element 106 extends
rearwardly from the leading edge spar 102. When fully deployed, the flexible
surface element 106 also extends from the fabric control subsystem which may
include a roller assembly 108 attached to an airframe to the wing-tip assembly
104
at the end of the spar 102. The flexible surface may be fabricated from the
same
materials described above in connection with the wing-tip mounted embodiment
of
the lift augmentation system. This embodiment of the lift augmentation system
may
increase the lift area of an airframe by more than 100%. In some applications,
this
embodiment of the lift augmentation system may prove the entire lifting
surface for
an airframe.
The roller assembly 108 may be rotated by a suitable conventional actuator
110, such as a DC motor. The roller assembly 108 is operable to furl or roll
up the
flexible surface element 106 when it is retracted to a stowed position and can
control
or brake the deployment of the flexible surface element as it is deployed to
the
position depicted in FIG. 9. As with the first embodiment, at least a pair of
flexible
surface elements 106, 107 (see FIG. 10) are provided, one 106 being on the top
or
suction surface, and the other 107 being on the bottom or pressure surface of
the lift
augmentation system.
The leading edge spar 102 has a cross-sectional shape that is smoothly
rounded and that functions as the leading portion of an airfoil. At the back
of the
leading edge spar 102 a pair of brackets 112, 114 are provided to support the
corresponding forward edge of the associated flexible element 106, 107. To
this
end, the brackets 112, 114 may, for example, be fashioned by an extrusion
process.
Regardless of how the brackets 112, 114 are fabricated, each bracket includes
a
corresponding channel 116, 118 to receive and hold an enlarged edge 120, 122
of
the associated flexible member 106, 107. Each bracket 112, 114 also includes a
plurality of bearing races 130, 132, 134, 136. The bearing races 132, 138
oppose
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one another, as do bearing races 134, 136. Moreover, the bearing races 130,
132,
134, 136 circumscribe the channel 116. Thus, when viewed in cross section, the
brackets 112, 114 define a rearwardly projecting finger extending from a
position
adjacent to the upper and lower surfaces, respectively, of the leading edge
spar 102.
As illustrated (see FIG. 9), the flexible surface elements 106 may taper from
the root of the wing at the pivot 100 to the tip of the wing at the plate 104.
So that
the entire flexible surface elements 106, 107 can be retracted, the roller
assembly
108 has a length sufficient to wrap the widest part of the flexible surface
element
106. Preferably, the upper and lower flexible surface elements 106, 107 are
joined
at the trailing edge 150, or within a distance of about 10% of the chord
length of the
lift augmentation system cross section. That connection helps the flexible
surfaces
106, 107 retain an airfoil shape in cross section and helps reduce the
possibility of
separation between the suction and pressure surfaces at the trailing edge.
If desired, the upper and lower flexible surface elements 106, 107 may have
one or more battens 152. The battens 152 can be spaced at intervals along the
leading edge spar 102. When used, the battens 152 help stiffen the flexible
surface
elements and help preserve an airfoil shape. As an alternative, vertically
extending
fabric webs may be provided at intervals along the spar 102 to regulate the
spacing
between the upper and lower surface elements 106, 107. Such fabric webs may be
a
substantially continuous cross-section of the desired airfoil shape, or
material strips
spaced chordwise and attached to both the upper and lower surface elements
106,
107.
To exend the flexible surface elements 106, 107 to the deployed position, a
headboard 154 (see FIG. 9) is attached to the outboard end of both surface
elements
106, 107. The headboard 154 securely clamps the ends of the surface elements
106,
107 together (see FIG. 11). In addition, the headboard 154 includes a
plurality of
linear reduced friction bearings 160, 162, 164, 166, 168, 170, 172, 174 that
cooperate with the bearing races 132, 134, 136, 138 (see FIG. 10) provided on
each
of the brackets 112, 114. Those bearings allow low friction sliding to occur
between
the headboard 154 (see FIG. 11) and the leading edge spar 102. Moreover, the
bearings are arranged in the headboard 154 so that a longitudinal axis 180 of
the
headboard 154 defines a fixed angle with a chord 182 of the lift augmentation
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system. For these purposes, the chord is taken as a line through the
forwardmost
point of the leading edge spar 102 and the trailing edge of the flexible
surface
elements 106, 107. With this arrangement, the headboard 154 also fixes the
angle of
attack for wing-tip of the lift augmentation system system.
This embodiment of the lift augmentation system is also movable between a
first position (see FIG. 12) and a second position. Here, the first position
is fully
retracted (shovnnn in phantom lines). In the second position, the leading edge
spar
102 is fully extended and is generally perpendicular to the axis of the roller
assembly 10~. To rotate the leading edge spar from the retracted position 102'
to
the extended position, a cable-and-pulley arrangement may be used. For
example,
one end of a flexible deployment cable 190 may be attached to the leading edge
spar
102 inboard of the outboard end of the spar 102. Preferably, the cable-to-spar
connection is located at about the middle of the distance between the pivot
100 and
the outboard end of the spar 102. The deployment cable 190 passes around a
pulley
192 mounted to the housing 194 and then goes into the housing 194 where it is
wound on a suitable conventional winding mechanism (not shown). As the
deployment cable 190 is wound in, the leading edge spar 102 rotates about the
pivot
100 from the first position 102' to the fully deployed position.
The deployment system also includes a second cable, the luff tensioning
cable 200. One end of the Tuff tensioning cable 200 is attached to the
headboard
154. The Tuff tensioning cable then passes around a pulley 202 carried at the
downstream end of the wing-tip assembly 104, and around another pulley 204
carried at the end of the leading edge spar 102. The luff tensioning cable 200
then
passes internally through the leading edge spar 102 to the housing 194 where a
suitable conventional cable winder (not shown) is provided.
After the leading edge spar 102 has been extended, the luff tensioning cable
200 is wound in. Initially the headboard 154 is held in its stowed position.
As the
luff tensioning cable tightens, the wing-tip assembly 104 rotates about its
pivot 206
from the stowed position 104' where it is in substantial longitudinally
alignment
with the leading edge spar 102 to its deployed position where it extends
rearwardly
from the leading edge spar 102. Preferably the outboard surface of the wing-
tip
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assembly 104 and the forward most edge of the leading edge spar 102 are
substantially perpendicular at full deployment.
Continued winding of the tuff tensioning cable 200 causes the headboard
154 to be drawn outwardly along the leading edge spar 102 until the flexible
surface
elements 106, 107 are fully deployed (see FIG. 9). As the headboard 154 moves
along the leading edge spar 102, the linear bearings move along the brackets
112,
114 (see FIG. 11) and the enlarged edges 120, 122 of the flexible surface
elements
106, 107 are pulled longitudinally through the corresponding slots 116, 118.
With
final tensioning of the cable 200, the trailing edge 150 (see Fig. 10) of the
flexible
surface elements 106, 107 is held in proper spatial relation to the leading
edge spar
102 so that the desired airfoil shape of the lift augmentation system cross
section is
attained.
The flexible surface elements 106, 107 can be retracted by easing tension on
the cable 200 and actuating the roller 108 to wind in the elements 106, 107.
Moreover, to retract the leading edge spar, aerodynamic drag can be used to
swing
the spar about its pivot 100 when tension on the cable 190 is eased.
It will be appreciated by those skilled in the art that it would also be
possible
to use hydraulic actuators for the spar deployment subsystem so that the
leading
edge spars can be retracted with a powered and controlled system.
This second embodiment of the lift augmentation system is well-suited for
use with an airframe having short stubby wings or no wings. For example, a
helicopter with no wings may be provided with a lift augmentation system of
this
pivotally deployed embodiment. One lift augmentation system would be mounted
on each side of the helicopter with the stowed position having the leading
edge spar
against the helicopter fuselage. When deployed the lift augmentation system
extends laterally outwardly from the helicopter body or fuselage. A mirror
image
lift augmentation system is provided on the other side of the helicopter.
These lift
augmentation systems are lightweight and can be used to facilitate quiet
operation of
the helicopter. More particularly, with the wings deployed, the helicopter can
operate in an autorotation mode to reduce noise from the main rotor while the
flexible wings provide a glider-like operability. In this application, the
lift
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augmentation system provides substantially the entire lifting surface area for
the
helicopter - except for the main rotor blades.
The second embodiment of the lift augmentation system may also be used
for an independently mountable wing assembly for use with structures or
airframes
that have not been designed with wings and for which some gliding capability
is
desired. Examples of such structures are lifting bodies, air-dropped cargo
containers
and the like. For these applications, the lift augmentation system provides
the entire
lifting surface area for the airframe.
For such applications, wing assembly 220 comprising a pair of lift
augmentation systems symmetrically arranged with respect to one another (see
FIG.
13) can be used. The leading edge spars 102, 102" of the wing assembly 220
rotate
between the retracted positions 102', and 102"', respectively, as discussed
above.
Deployment of the flexible surface elements 106, 106' may be coordinated. For
example, the roller assemblies 108, 108' may have gears 210, 212,
respectively, that
are engaged with one another to ensure that the deployment and tensioning of
the
two sides of the wing assembly 220 are symmetrical. If the application
requires that
the lift augmentation system s of the wing assembly 220 have a swept-back
configuration, that configuration is readily accomplished by arranging the
angle
between the axes of the roller assemblies 108, 108' at twice the desired sweep
angle
for the leading edge spars 102, 102".
To support the spars 102, 102" in a high-wing position, each lift
augmentation system may have a vertical strut 222, 224 which carries the
associated
pivot 100, 100'. In addition, spar-support struts 230, 232 may be provided
extending between the associated leading edge spar 102, 102' and the bottom of
the
struts 230, 232. With this arrangement, the spars 102, 102' can be constrained
to
move in a plane to which the pivot axis is perpendicular.
Turning to FIG. 15, an air-droppable container 250 is shown having a
rectangular prismatic shape. Any other suitable conventional shape is also
contemplated including, for example, circularly cylindrical, prisms with
semicircular, trapezoidal, or triangular cross sections. If desired, a fairing
may be
attached to the forward end of the container 250. Similarly, if desired, a
fairing or
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directional control structure 252 may be attached to the back end of the
container
250 to provide vertical and horizontal stabilization surfaces.
To increase the lateral range of the container during an air-drop, a flexible-
wing lift augmentation system 220 is attached to the top of the container 250.
To
some extent, the wing system 220 converts the container 250 to a glide
vehicle. The
lift augmentation system is stowed in a pod 254 at the time the container
starts
dropping and is deployed to the position shown by remotely controlled
apparatus.
The struts 230, 232 support the wing 220 both laterally and longitudinally
with respect to the container 250. To that end, suitable support struts and
elevatable
arms are provided, some of which can be located within fairings around the pod
254
and its vertically extending portions. Those support struts and arms may be
further
operable to adjust the elevation of the front and rear portions of the pod 254
so that
the angle of attack for the wing 220 can also be controlled and/or adjusted.
The wing assembly 220 may be positioned generally at the center of the
container 250.
The lift augmentation system of this invention provides substantial
advantages. For example, testing of the lift augmentation system has confirmed
a
substantial reduction in ground run can be attained - on the order of 40% --
and that
a significant reduction in take-off speed can also be achieved - on the order
of 32%
in certain applications. Flight test simulations also indicate that the
takeoff distance
to cleas a 50-foot obstacle can also be materially reduced - on the order of
40%.
Landing performance with the lift augmentation system has even more improved
metrics than take-off.
Similar controlled descent performance capabilities of the top-mounted lift
augmentation system in a pod make it a competitive candidate for application
to
space re-entry or to airdrop cargo operations. The pod-mounted lift
augmentation
system offers a small, compact unit for easy handling and shipping yet
provides
wing area for lift and autonomous descent control for accurate placement on
target.
Other advantages for the "wing-tip lift augmentation system" include
realization of significant gains in wingspan and aspect ratio, thereby
efficiently
improving the lift to drag relation. In the retracted mode, the wing-tip lift
augmentation system provides a short, low aspect ratio and low drag profile
which
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configures an aircraft for speed. Conversely, when deployed, the wing
extensions
increase the aspect ratio to optimize high lift and slow flight in a "loiter"
mode. The
extended configuration is advantageous for short field operations and long
endurance applications. Importantly, the wing-tip lift augmentation system
provides
the opportunity for in-flight deployment at reduced power for slow, long
endurance
loiter capability or transitions between loiter and higher speed operational
modes.
Further advantages of the lift augmentation system are that the system is not
airframe platform dependent and that the speeds in the retracted configuration
are
better than the rotary wing craft. For military applications, the lift
augmentation has
the further advantages of near-silent operation with the concomitant tactical
potential.
It will thus be apparent that a new lift augmentation system has been
described above. Moreover, it will be apparent to those skilled in the art
that
numerous modifications, variations, substitutions, and equivalents exist for
various
features of the invention. Accordingly, it is expressly intended that all such
modifications, variations, substitutions, and equivalents that fall within the
spirit and
scope of the invention, as defined by the appended claims, be embraced
thereby.
