U.S. patent application number 10/300916 was filed with the patent office on 2003-06-05 for aircraft noise reduction apparatus.
This patent application is currently assigned to AIRBUS UK LIMITED. Invention is credited to Chow, Leung C., Foot, David A., Wood, Christopher N..
Application Number | 20030102406 10/300916 |
Document ID | / |
Family ID | 10856859 |
Filed Date | 2003-06-05 |
United States Patent
Application |
20030102406 |
Kind Code |
A1 |
Chow, Leung C. ; et
al. |
June 5, 2003 |
Aircraft noise reduction apparatus
Abstract
An aircraft, aircraft landing gear and apparatus including at
least one attachment (15,17,76,93,94,111) for noise reduction
purposes are provided. Such attachments are shaped and positioned
on the landing gear to deflect air away from noise-inducing
components (64,65) of the landing gear and to permit deflection and
articulation movement and also stowage of the landing gear whilst
the attachments are installed thereon. The attachments are not
designed to be drag-reducing.
Inventors: |
Chow, Leung C.; (Bristol,
GB) ; Foot, David A.; (Bristol, GB) ; Wood,
Christopher N.; (Nr Congleton, GB) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Assignee: |
AIRBUS UK LIMITED
|
Family ID: |
10856859 |
Appl. No.: |
10/300916 |
Filed: |
February 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10300916 |
Feb 6, 2003 |
|
|
|
09655347 |
Sep 5, 2000 |
|
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Current U.S.
Class: |
244/100R |
Current CPC
Class: |
B64C 2025/003 20130101;
B64C 25/16 20130101; B64C 25/001 20130101 |
Class at
Publication: |
244/100.00R |
International
Class: |
B64C 025/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 1999 |
GB |
9915977.4 |
Jun 29, 2000 |
PCT/GB00/02525 |
Claims
1. Aircraft noise reduction apparatus including at least one
noise-reducing attachment (15,17,76,93,94,111) for landing gear of
the aircraft shaped for positioning on the landing gear to deflect
air away from noise inducing components of the landing gear and to
permit deflection, articulation movement and stowage of the landing
gear with the attachment installed.
2. Apparatus as in claim 1 in which a said attachment comprises a
deflector screen (15,17,76,93,94,111) adapted not to completely
surround noise inducing components on the landing gear.
3. Apparatus as in claim 1 or 2 in which the attachment comprises
an axle attachment (15) positionable in front of an axle (3) for
nose gear of the aircraft.
4. Apparatus as in claim 3 in which the axle attachment is shaped
to enclose a towbar fitting (24).
5. Apparatus as in claim 3 or 4 in which the axle attachment
includes generally cylindrical wheel extensions (30,31) extending
between a central portion (32) thereof and each wheel (33).
6. Apparatus as in claim 1 or 2 in which the attachment comprises a
steering mechanism attachment (17) for positioning in front of a
steering mechanism for the landing gear.
7. Apparatus as in claim 1 or 2 including an apertured strut
attachment (16) positionable over a said aperture (40) in the strut
(14) to deflect air away from edges (41,42) of the aperture.
8. Apparatus as in claim 7 in which the attachment (16) is shaped
to blend in airflow leaving the attachment with airflow passing
over streamwise extending surfaces (45,46) of the strut, when in
use.
9. Apparatus as in claim 7 or 8 in which the attachment (16) is
shaped to deflect air away from noise-inducing elements on the
landing gear positioned to the rear of the said strut (14).
10. Apparatus as in any preceding claim in which the attachment
(15,17,76,93,94,111) is shaped to avoid regions of air stagnation
thereover, when in use.
11. Apparatus as in any preceding claim including an undertray
attachment (76) shaped to extend in front of and underneath a bogie
beam (71) of the landing gear.
12. Apparatus as in claim 11 in which the undertray (76) includes a
forward upwardly extending aerodynamic surface (82) blended
smoothly into an undersurface (83) extending underneath and along
the bogie beam with a further laterally facing surface extending
longitudinally of the bogie beam on either side of the undertray
(89,90) depending from lateral edges (87,88) of the undertray.
13. Apparatus as in claim 11 or 12 in which the undertray (76) is
attachable to axles (72,73) on the landing gear bogie by means of
band-type clamps (79,80) adapted to pass around the axle/bogie beam
and through at least one part-annular chamber (99,100) formed in an
extension piece fixed to the undertray.
14. Apparatus as in any preceding claim including a pair of
articulating fairing attachments (93,94) for attachment to a
forward articulation link (67,68) of a bogie of the landing gear,
one articulated fairing being mounted to each articulation link
with an aerodynamically contoured interface (105) being defined
between the fairings comprising a generally spherical element (106)
on one fairing (94) co-operating with generally circular section
(107) tubing of the other fairing (93).
15. Apparatus as in claim 14 when dependent upon any one of claims
11 to 13 in which the undertray (76) and lower articulation link
fairing (93) in use lie closely adjacent one another with the
landing gear bogie (71) in its approach-to-landing
configuration.
16. Apparatus as in any preceding claim including a door attachment
(111) attachable to a door (112) which is attached to the landing
gear, the door extending generally streamwise to one side of the
landing gear, the door attachment (111) being positionable to
extend from the door in front of at least a main leg (64) of the
landing gear.
17. Apparatus as in claim 16 in which the door attachment (111) is
adapted for sealing engagement with the door (112).
18. Aircraft landing gear including apparatus according to any
preceding claim.
19. Aircraft landing gear as in claim 18 in which at least one said
attachment is shaped and positioned such that airflow over the
attachment (16) during flight leaves the attachment substantially
in the free steam direction.
20. Aircraft landing gear as in claim 18 or 19 in which at least
one said attachment (111) is positioned to deflect incident air
away from an air accelerating region formed between two components
(64,65) of the landing gear.
21. Aircraft including landing gear according to any of claims 18
to 20.
Description
[0001] This invention relates to aircraft noise reduction
apparatus, in particular to apparatus to reduce noise emanating
from landing gear of the aircraft when deployed on approach to
landing.
[0002] The invention has particular application to commercial
aircraft when landing at airports in or near to built up areas
where aircraft approach noise is an increasing nuisance with
increasing frequency of use of airports and ever larger aircraft.
Noise emanating from commercial aircraft, whether cargo aircraft
and/or passenger carrying aircraft, is now an important
environmental issue. The increasing frequency of use of airports
has led to aircraft of increasing size being used. This in turn has
led to greater noise being generated by each aircraft in its
approaches to the airport. Modern high bypass ratio turbofan
engines are now extremely quiet on approach to landing and dominant
noise on some aircraft types, perceived at ground level, is
starting to become the noise generated by landing gear and by high
lift devices on the wings.
[0003] This invention addresses the problem of aircraft noise, as
perceived at ground level, generated by landing gear. Although
noise is likely to be induced by any element which creates
turbulence in the airflow past the landing gear, those elements
which have been found particularly likely to create high noise
levels are as follows:--elements which act as Helmholz resonators
such as hollow axles, apertures, fastener fittings, spindles, etc;
also elements likely to create small vortices such as small
protuberances, sharp edges; dresssings such as small pipes, tubes,
cables, and coil springs, etc. All such features are to be found
aplenty on modern landing gear and tend to be more prevalent in the
region of steering gear and wheel axles.
[0004] Although wind tunnel tests have been carried out on landing
gear fully enclosed by fairings to determine noise levels in the
far field, such full enclosure fairings are normally completely
impractical for everyday use on an aircraft. This is because
articulation of the landing gear during deployment and retraction
movement is prevented by the fairings and because very limited
stowage space in the landing gear bay in most aircraft will not
accommodate full enclosures owing to the space which they take up.
Additionally, full enclosure fairings render daily visual
inspection regimes and maintenance of the landing gear almost
impossible. Firstly, this is because visible inspection through
such fairings is generally impossible and secondly because regular
removal of such fairings for inspection or maintenance is far too
time consuming and difficult. To date therefore no practical
solution to the problem of landing gear induced airframe noise has
been found.
[0005] According to a first aspect of the invention there is
provided aircraft noise reduction apparatus including at least one
noise-reducing attachment for landing gear of the aircraft shaped
for positioning on the landing gear to deflect air away from noise
inducing components of the landing gear and to permit deflection,
articulation movement and stowage of the landing gear with the
attachment installed.
[0006] The attachments may comprise deflector screens adapted not
to completely surround noise inducing components on the landing
gear. The said lack of a complete surrounding being for the
purposes of allowing the said access and foldability of the landing
gear.
[0007] Induced noise is proportional to the sixth power of the
relative velocity of the airflow and component around which the air
flows, and attachments of the invention are positionable to deflect
incident air away from noise inducing components, preferably into
the free stream.
[0008] The attachments must withstand all aerodynamic loads and
foreign object damage, and it will be appreciated that the use of
attachments according to the invention may increase landing gear
drag.
[0009] Preferably a said attachment is shaped such that when
positioned on the landing gear, airflow over the attachment during
flight leaves the attachment substantially in the free stream
direction.
[0010] Preferably a said attachment is shaped to avoid or minimise
an air stagnation region forming in front thereof when positioned
on the landing gear and in use. Such stagnation regions tend to
increase both drag and noise emanating downstream of the stagnation
region. The term "in front of" as used herein refers to a position
upstream in the airflow, during flight.
[0011] In regions of the landing gear where incident air is
accelerated between components of the landing gear, such as struts,
stays and actuators, at least one said attachment is preferably
positioned to deflect incident air away from the said
air-accelerating region. In this way any noise-inducing components
of the landing gear positioned in the said air-accelerating region
will not be subject to the passage of such accelerated high speed
air past them.
[0012] The apparatus may include an axle attachment positionable in
front of an axle for nose gear of the aircraft to deflect air away
from noise inducing components such as landing gear dressings in
the region of the axle.
[0013] The axle attachment may be shaped to shield items such as a
towbar fitting on the nose gear and the said shaped portion is
desirably separately removable or pivotable out of the way in order
to provide access to such a towbar fitting without disturbing the
remainder of the axle attachment. Cam fasteners or other quick
release fittings are suitable for fastening the shaped portion.
[0014] The axle attachment may extend laterally into close
proximity with the wheels and may include generally cylindrical
wheel extensions extending between a central portion thereof and
each wheel whereby to deflect air away from noise inducing
components on the axle and at the same time to deflect air away
from a cavity formed within each wheel.
[0015] The wheel extensions preferably extend into close proximity
with a rim of each wheel. Alternatively the wheels may be fitted
with inner hub caps or wheel fillers. Such fillers may be of say
foam material formed in two opposing sections with wedge-shaped
elements driven into position therebetween. The foam or like
material is preferably covered on the outside with a weatherproof
material.
[0016] The axle attachment may include upper extension portions for
positioning on either side of a main leg of the nose gear to
deflect air away from torque link attachments usually sited on the
axle.
[0017] The apparatus may include a said attachment positionable in
front of a steering mechanism for the landing gear. Such a steering
mechanism has been found to be prone to noise inducement including,
as it usually does, many sharp edges, apertures and sundry pipe and
cable work.
[0018] Similarly, the axle attachment deflects air away from
another region of the landing gear particularly prone to noise
inducement, i.e. the joint between the main leg and the axle, again
liable to include sundry sharp edged fittings and pipe and cable
work.
[0019] For circular landing gear components such as main legs or
actuators positioned immediately in front of noise inducing
components, transition strips of tape may be attached to the
circular component on either side thereof to encourage clean
detachment of airflow therefrom and to encourage airflow away from
a region immediately behind the circular component.
[0020] Where articulation and stowage permits it, components such
as circular legs or actuators may be fitted with trailing
extensions from either side thereof. Such extensions, in
combination with the component, may then act as an attachment
according to the invention to deflect air away from noise inducing
components behind the said component with trailing extensions.
[0021] The said apparatus may include at least one said attachment
positionable in front of an apertured landing gear strut or stay to
deflect air away from edges of the aperture.
[0022] For a said strut or stay having surfaces extending
approximately streamwise in the airflow a said attachment may be
shaped to blend in airflow leaving the attachment with airflow
passing over the said streamwise extending surfaces. Alternatively,
where further noise inducing elements are positioned on the landing
gear to the rear of the said attachment, the attachment may be
flared or otherwise shaped also to deflect air away from the said
rearward noise inducing elements. In this regard it has been
determined that for an attachment to accelerate incident air is not
unacceptable so long as the accelerated air does not pass over
noise-inducing components.
[0023] A said attachment whilst being shaped to avoid any regions
of air stagnation where possible may also be shaped or flattened as
appropriate to avoid other elements of the landing gear or further
attachments, during movement such as articulation and/or stowage of
the landing gear.
[0024] Where the landing gear includes a wheeled bogie having a
bogie beam the apparatus may include an attachment in the form of
an undertray extending in front of and underneath the bogie beam to
deflect air away from noise inducing elements in the region of the
bogie beam, for example brake rods, bearings and their mountings,
other fittings and sundry pipe and cable work.
[0025] An advantage of the undertray not extending above and behind
the bogie beam is that inspection and maintenance access and air
cooling are not thereby prevented by the attachment.
[0026] Where the bogie beam is tilted upwardly at the front, during
approach, the area of the bogie beam left exposed is downstream of
the undertray and thus the passage of high speed air past noise
inducing components associated with the bogie beam is prevented by
the undertray attachment.
[0027] Preferably the undertray includes at least one door therein
to provide access to concealed items such as jacking points for the
bogie.
[0028] The undertray may have a single curvature aerodynamic
surface and may be of a width to permit air to pass between the
undertray and wheels on the bogie to cool brakes. Preferably the
undertray includes a forward upwardly extending aerodynamic surface
blended smoothly into an under surface extending underneath and
along the bogie beam, desirably with a further surface extending
longitudinally of the bogie beam on either side of the undertray
depending from lateral edges of the undertray, preferably
orthogonal to the said aerodynamic surface. In this way air
spilling over each lateral edge of the undertray in the region of
wheel brakes will be able freely to flow past the brakes but will
not be accelerated past the brakes by any funnelling effect of the
surface contours of the undertray.
[0029] Where the bogie includes a pair of forward articulation
links a said attachment may comprise a pair of articulating
fairings, one mounted to each articulation link with an
aerodynamically contoured interface being defined between the
fairings. Preferably the said interface comprises a generally
spherical element on one fairing co-operating with generally
circular section tubing of the other. The spherical element
desirably has its centre coincident with a pivot axis between the
articulating links.
[0030] Where the landing gear includes a door attached thereto
extending in a generally streamwise direction to one side of a main
leg of the landing gear a said attachment may comprise a deflector
fairing extending from the door in front of at least the main leg
of the landing gear. Preferably the fairing is positionable in
sealing engagement with the door and may additionally extend in
front of any further struts, stays and/or actuators for the landing
gear located in the vicinity of the main leg thereby to deflect air
away from all said landing gear components. For a main landing gear
having a drag stay extending upwardly in the vicinity of the main
leg and a retraction actuator similarly extending upwardly in the
vicinity of the main leg, the said fairing not only achieves
deflection of the air away from any noise inducing fittings on the
main leg, but also deflects air away from passages formed between
any combination of the main leg, the actuator, the drag stay and
the main leg door where air would otherwise be accelerated
therethrough usually past sundry noise inducing fittings.
[0031] For a large aircraft the undertray may be in excess of 2
metres in length and is desirably constructed to possess adequate
longitudinal and torsional stiffness to enable handling when off
the aircraft.
[0032] The front portion of the undertray desirably has extension
portions to extend around the lower articulation link fairing and
thus provide a smooth airflow in this area, upon approach to
landing. Generally a main landing gear with a bogie will approach
landing with the rear wheels deflected downwardly and the front
wheels deflected upwardly. The undertray and lower articulation
link fairing thus desirably lie closely adjacent one another when
the bogie is in approach configuration.
[0033] The undertray may be attachable to axles on the bogie,
and/or to the bogie beam itself by means of band-type clamps
adapted to pass around the axle/bogie beam and through at least one
part-annular chamber formed in an extension piece fixed to the
undertray.
[0034] In general, all attachments will be as easily removable as
possible, employing either existing screw-type fasteners on the
gear and/or clamps around items of the gear such as struts, stays
and axles. Some attachments will inevitably need to be removed for
maintenance, at some stage, and here ease of removal and re-fitting
is essential. All attachments are also preferably retro-fittable to
existing designs of landing gear.
[0035] According to a second aspect of the invention there is
provided aircraft landing gear including apparatus according to the
first aspect of the invention.
[0036] According to a third aspect of the invention there is
provided an aircraft incorporating landing gear fitted with
noise-reduction apparatus according to the first aspect of the
invention.
[0037] The invention will now be described by way of example with
reference to the accompanying drawings of which:--
[0038] FIG. 1 is an orthogonal view of nose landing gear fitted
with apparatus according to the invention,
[0039] FIG. 2 is an orthogonal cut away view of main landing gear
when fitted with apparatus according to the invention,
[0040] FIG. 3 is an orthogonal view of part of a nose landing gear
fitted with an attachment according to the invention,
[0041] FIG. 4 is a top plan view of a torque link with fairing
attachment,
[0042] FIG. 5 is a section along the line V-V of FIG. 4,
[0043] FIG. 6 is a section through a nose landing gear lower drag
stay with fairing attachment,
[0044] FIG. 7 is a side view of a landing gear articulation link
with fairing,
[0045] FIG. 8 is a side detail view of a front end of an undertray
attachment according to the invention,
[0046] FIG. 9 is a section taken along the line IX-IX of FIG. 8,
and
[0047] FIG. 10 is an orthogonal view of an aircraft main landing
gear with wheels removed to show landing gear dressings.
[0048] Referring to FIGS. 1 and 3, an aircraft nose landing gear is
shown having wheels 1, 2, an axle 3 (see FIG. 3), a main telescopic
leg 4, and steering mechanism shown generally at 5, an upper drag
stay 6 pivotally connected to a lower drag stay 7 at pivot 8 and to
the leg 4 at pivot 9, pintle bearings 10, 11, a drag stay release
mechanism 12 and torque links 13, 14. The nose gear is fitted with
various noise-reducing attachments as follows. All have been
designed to provide the most streamlined shape commensurate with
maximum total noise reduction and providing room for articulation
of the landing gear during use, during retraction/deployment and
during stowage. Drag may actually be increased owing to the fitting
of the attachments. Shown in FIGS. 1 and 3 is an axle fairing
attachment 15; a lower torque link attachment 16 (shown in FIG. 1
only); a steering mechanism attachment 17; steering actuator covers
18, 19; a lower drag stay attachment 20 and main fitting
attachments 21, 22.
[0049] Referring to FIG. 3, the axle fairing attachment 15 is
clamped around the leg 4 by a clamp (not shown). A lower hinged
portion 23 covers a towbar fitting 24 and may be hinged about the
axis 25 for access to the towbar fitting. An upper portion 26 of
the axle attachment 15 has extension portions 27, 28 positioned to
deflect incident air away from lower pivots 29 of the lower
articulation link 14. Cylindrical extensions 30, 31 extend between
a central portion 32 of the attachment and wheels 33. The
cylindrical extensions 30, 31 extend in close proximity with rims
117 of the wheels to prevent noise being generated by the passage
of incident air across Helmholz resonators formed by the
wheels.
[0050] External wheel cover attachments 34 extend into close
proximity with rims 35 of each wheel whilst not overlapping the
tyre 36, so that inspection of the tyres is not interfered with.
Such wheel covers may be annular in shape to fit around central
forced-air-cooling ducts for the wheels and may be mounted
thereon.
[0051] In FIG. 1 the lower torque link attachment 16 is generally
domed but with a scallop to provide clearance when the links 13 and
14 move together during compression of the main leg 4. Referring to
FIGS. 4 and 5 such an attachment as that shown at 16 is shown
bolted into position using bolts 37, 38 passing through the
attachment 16 for fastening behind a backing plate 39 placed behind
an aperture 40 in the torque link 14. Edges 41, 42 defining the
aperture 40 are therefore covered by the attachment 16, just as are
edges 43, 44. It will be noted that streamwise extending surfaces
45, 46 are blended in with the attachment 16 such that air leaving
the attachment at positions 43, 44 blends with free stream air
passing over surfaces 45, 46.
[0052] The steering mechanism attachment 17 is a generally domed
shape formed to minimise any stagnation areas centrally thereof.
Edge region 47 is shaped and positioned to merge air leaving the
attachment with free stream air, tangential thereto. The region of
the landing gear behind the attachment 17 is prone to noise
generation and this attachment is effective for reducing noise
emanating from the landing gear.
[0053] Steering actuator covers 18, 19 have domed ends 48, 49 and
smoothly curving portions 50, 51 covering actuator tubes (not
shown) and sundry pipework (not shown).
[0054] Referring to FIGS. 1 and 6, the lower drag stay 7 has a
fairing attachment 20 positioned in front thereof. The attachment
20 is not designed to fit closely with the drag stay 7 but is made
deliberately wider to deflect air not only past edges 52, 53 but
also away from coil springs 54, 55 of the drag stay release
mechanism 12. It will be noted that edge regions 56, 57 of the
attachment 20 are shaped to blend in air leaving the attachment
with free stream air. The coil springs 54, 55 may be fitted with
socks, preferably transparent for inspection purposes, to reduce
induced noise.
[0055] Lastly, main fitting attachments 21, 22 cover apertures
defined between the main leg 4, diagonal bracing member 58 and a
pintle member 59. The main fitting attachments are relatively
planar on their front surface to allow space for articulation of
the nose gear during retraction and stowage.
[0056] It will be seen that the fitting of relatively brief fairing
attachments to the nose gear has had the effect of covering many
quite troublesome areas of noise generation but that these
attachments may be easily removed for access and are in all cases
designed to allow for compression of the main leg and articulating
movement of the nose gear and stowage thereof in its stowage bay
(not shown). It will be noted that in all cases the attachments are
designed to be retro-fittable to an existing landing gear, clamping
having been used throughout as a method of attachment.
Additionally, the relatively small size of the attachments~has kept
additional weight to a minimum.
[0057] The skilled reader will note that the upper drag stay 6 has
no fairing attachment thereon. This part of the drag stay is
largely contained within the fuselage of the aircraft.
[0058] Upper torque link 13 has not been fitted with a fairing
attachment as it lies at least partly behind the steering mechanism
attachment 17. Clearly an attachment could be fitted to this part
of the linkage if the particular landing gear design would
substantially benefit from it.
[0059] Referring to FIG. 10, an aircraft main landing gear is shown
minus wheels but with its dressings 60, 61, 62, 63 shown. The
landing gear comprises a main telescopic leg 64, a retraction
actuator 65, a drag stay 66, upper and lower articulation links 67,
68, upper and lower torque links 69, 70, a bogie beam 71, axles 72,
73 and brake rods 74, 75.
[0060] Dressings 62 are largely out of the airflow and do not
significantly affect noise levels from the landing gear. Dressings
60, 61, 63 are in the airflow when the landing gear is deployed on
approach and are sources of noise from the landing gear, especially
when combined with other components. It is believed that vortices
shed from dressings impact on to other components then to generate
noise.
[0061] Referring now to FIGS. 2, 7, 8 and 9, a main landing gear
similar to the one shown in FIG. 10 is shown with various
noise-reducing fairing attachments fitted, together with details of
certain attachments. Referring to FIG. 2, parts common to FIG. 10
have been shown with identical reference numerals. An undertray
attachment 76 is shown clamped to the bogie beam 71 by clamps 77,
78 and also by clamps 79, 80 (see FIGS. 8, 9) to the axles 72, 73.
The undertray 76 has a single curvature aerodynamic surface 81
extending over a forward upwardly extending portion 82 and a lower
portion 83 extending under the bogie beam. A rear curved portion 84
keeps incident air away from the rear axle 73 and its dressings 61
(see FIG. 10). The undertray has a pair of openable access doors
85, 86 for access to jacking points (not shown). Depending from
lateral edges 87, 88 of the undertray are a pair of laterally
facing surfaces 89, 90 extending longitudinally of the bogie beam
on either side of the undertray. The forwardly upwardly extending
portion 82 has extensions 91, 92 wrapping around a lower
articulation link fairing attachment 93 which works in conjunction
with an upper articulation link fairing attachment 94. With the
landing gear in the approach position as shown in FIG. 2 it can be
seen that the forward portion 82 of the undertray wraps neatly
around the lower articulation link fairing attachment 93 to provide
a smooth aerodynamic contour of low noise configuration. It will be
appreciated that the forward portion 82 of the undertray
effectively deflects incident air away from the dressings 60.
[0062] The undertray is of a width to permit air to pass between
wheels 95, 96 and the undertray for brake cooling. The form of the
edges 87, 88 and longitudinally extending surfaces 89, 90 permits
air to pass over brake callipers (not shown) between the undertray
and the wheels but does not funnel air through these regions at
increased speed and therefore create unnecessary noise. The shape
of the undertray is generally adapted to deflect air away from
noise inducing components on the bogie beam and landing gear
generally whilst affording maximum access to the upper and side
parts of the bogie beam for inspection and maintenance purposes.
Weight saving is also achieved by this configuration, relative to a
full enclosure.
[0063] The clamps 79, 80 for clamping the undertray to the axles
72, 73 comprise bands 97, 98 passing through part annular elements
99, 100 attached to the undertray (see FIGS. 8 and 9). This method
of fitting is extremely rigid, robust and of relatively light
weight.
[0064] The articulation link fairing 93, 94 is shown in FIG. 2 and
also in more detail in FIG. 7. It will be appreciated that the
articulation links 67, 68 (see FIG. 10) work in conjunction with
telescopic compression of the main leg 64. For this reason the
fairing attachments 93, 94 must be able to pivot with respect to
each other. Each is separately clamped to its articulation link by
clamps 101, 102, 103, 104 (see FIG. 7) but the two interact with
each other in region 105 about the pivot centre. It will be seen
that upper attachment 94 has a part spherical portion 106 adapted
to pass inside a co-operating part cylindrical portion 107 of the
lower attachment 93 during pivoting movement of the articulation
links. The centre of portions 106 and 107 coincides with the pivot
centre of the articulation links. A clearance of 2 mm is preferred
between portions 106, 107. Edge regions 108, 109 of the attachment
are designed to deflect air leaving the attachments 93, 94 away
from noise-inducing elements on the main leg 64.
[0065] Referring to FIG. 2, forward drag stay 110, retraction
actuator 65 and main leg 64 are all shielded from the airstream by
a door deflector attachment 111 attached in sealing engagement to a
wing skin door 112 attached to the main leg 64. Owing to the way
the landing gear is stowed in the bay, space is extremely tight in
this area and the deflector attachment 111 achieves the object of
deflecting air away from the main leg, the actuator and the forward
drag stay without interfering with the stowage of the gear. Air
which would otherwise have been accelerated between any combination
of the leg, the retraction actuator, the forward drag stay and the
door is therefore deflected away from such potential noise-inducing
"channels" and around the main leg 64 into the free stream. The
attachment 111 is clamped by through bolts to the forward drag stay
110 and comprises a first portion 113 having a generally concave
aerodynamic surface 114 and a second portion 115 having a generally
convex aerodynamic surface 116.
[0066] Once again it will be seen that with relatively minimal use
of retro-fittable and easily removable attachments according to the
invention that all major noise-inducing areas of the landing gear
have been protected from the airflow. At the same time articulation
and stowage of the landing gear has not been hindered and
additional weight has been kept to a minimum.
* * * * *