Aircraft window erosion shield

AIRCRAFT WINDOW PROTECTIVE SHIELD

TECHNICAL FIELD The present invention relates generally to aircraft, and more specifically to aircraft windows.

TECHNICAL STATUS In conventional commercial aircraft, several windows are distributed along both sides of the fuselage, from the flight deck to just before the tail. The fuselage is tubular and varies in diameter or radius between the front and rear ends of the aircraft, and therefore the size and curvature of the windows also vary throughout the body of the aircraft.

Each window includes a frame suitably mounted in a corresponding opening in the aircraft's outer casing, and each frame firmly supports a corresponding pane.

Conventional aircraft housings are made of a high strength metal such as aluminum, and the typical window frame is also made of a high strength metal. Therefore, various metal fabrication methods are used to fabricate individual window assemblies for different size and strength requirements, depending on the specific location of the window along the aircraft body.

[0005] The weight of the aircraft directly affects aircraft efficiency during flight, and therefore aircraft have been continuously developed to reduce weight while providing sufficient strength of various aircraft components to enjoy long service life. during the commercial operation.

In addition, the operating cost of commercial aircraft is a major design goal, especially with the continuously increasing fuel increase. The initial cost of manufacturing the aircraft itself is also an important design goal, with both the cost of initial aircraft acquisition and the subsequent cost of operation being significant criteria in the competitive assessment of the aircraft and its expected lifetime low cost operation. useful.

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Accordingly, it is desired to offer a lightweight composite aircraft window frame, and a protective shield for it.

DISCLOSURE OF THE INVENTION This is an erosion shield for an aircraft window which includes an annular strip having a radially outer edge and a radially inner clamp. The shield is sized to cover a composite window frame having an outer edge and an inner frame around a central opening for receiving a window pane. The clip is asymmetrical around the central opening to protect the frame and allow the shield to be mounted on it.

BRIEF DESCRIPTION OF THE DRAWINGS The invention according to preferred and exemplary embodiments, together with its additional objects and advantages, is described more particularly in the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates an example of a commercial aircraft in flight, with an enlarged sectional elevation view of one of several windows found on the aircraft.

Figure 2 is an elevation view on the outside of the exemplary window shown in Figure 1 mounted on a part of the fuselage along line 2-2.

Figure 3 is an isometric view, partially in section, of the exemplary window illustrated in Figure 2, separated from the aircraft.

Figure 4 is an enlarged cross-sectional view of a portion of the window illustrated in Figure 3 and along line 4-4.

Figure 5 is a schematic view of the aircraft window illustrated in Figure 3 showing enlarged cross sections of the erosion shield mounted to the frame in an exemplary embodiment.

Figure 6 is a further enlarged cross-sectional view of an exemplary portion of the erosion shield attached to the support frame.

Figure 7 is a schematic view of a method for cold rolling forming a flat sheet metal ring in the erosion shield

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3/19 unitary annulus illustrated in the various Figures.

Figure 8 is a schematic view of a common erosion shield sized and configured for identical use with three common window frames of different curvature.

MODE (S) FOR CARRYING OUT THE INVENTION Figure 1 illustrates an example of an aircraft or aircraft 10 powered by gas turboprop engines in flight. The aircraft includes several windows 12 arranged in rows along both sides of the fuselage or outer shell 14 from the front end of the aircraft cockpit to just before the rear tail.

[0011] The windows maintain the cabin pressure integrity and protect passengers within the cabin from the external environment, including the rapid external airflow 16 passing over the outer casing during aircraft flight.

Each window is properly mounted through a corresponding opening in the aircraft housing 14, and the windows vary in size and configuration along the aircraft body. Since fuselage 14 is generally cylindrical or tubular, it has an inner diameter, or radius A, which varies along the body of the aircraft from the pointed nose through the wide passenger body to the pointed tail.

Each window 12 is sized and configured specifically to match the local curvature or radius A of the aircraft housing, and therefore several different size windows are required for each aircraft, and must be manufactured with corresponding differences.

The various windows in the aircraft may have identical design, but may vary appropriately in configuration, including size and curvature. An example window 12 is initially illustrated in cross section in Figure 1 and in plan view in Figure 2. Each window includes a frame and unitary composite window 18 in which a conventional transparent pane 20 is suitably mounted. The frame 18 itself is properly mounted through the corresponding opening in the aircraft housing 14 and supports the glazing therein.

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The composite frame 18 is illustrated in more detail in an exemplary embodiment in Figures 3 and 4. The frame includes a radially outer annular flange or edge 22 and a radially inner annular flange or frame 24 surrounding a central aperture 26 which is sealed by the pane 20 mounted thereon.

The frame 24 is offset transversely of the outer edge 22 along its thickness T in common laminations along that thickness. The laminated outer edge and the frame include various blades or layers, 1 to 7, for example, extending laterally or radially therethrough along the radial geometry axis R of the frame.

The blades or layers are preferably different from each other transversely between the opposite inner and outer sides 28, 30 of the frame, which correspond to the inner side of the aircraft cabin and to the outer side of the aircraft housing.

The frame 24, shown in Figure 4, is raised above and transversely bridged to the lower outer edge 22 by an annular rib 32 around the entire circumference of the central opening 26. The inner side of the frame 24 and the rib 32 defines a central pocket 34 in which the pane 20 may be mounted. The sash 24, or sash bar, defines an annular miter in which the glazing 20 can be mounted and secured, and resists differential pressure exerted on the window from the pressurized cabin of the aircraft.

The outer edge 22, the frame 24 and the rib 32 are integral with each other in a single or unitary component, and are continuous in circumference around the central aperture 26 shown in Figures 2 and 3.

The integrated outer edge, frame and rib thus together define the vertical, front and rear columns or shoulders 36, 38 and upper and lower horizontal rails 40, 42 integrally joined at their opposite ends.

The shoulders 36, 38 are spaced sideways or horizontally along a minor axis 44 of the frame 18 and define the horizontal width W of the frame.

The two rails 40, 42 are spaced longitudinally or vertically along

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5/19 of a major major axis 46 of the frame and define the height or length L thereof.

The two lateral shoulders 36, 38 laterally connect the central opening 26, and the two rails 40, 42 provide an upper head and a lower threshold that vertically connect the central opening 26, and collectively the shoulders and rails completely surround the central opening 26 laterally or circumferentially.

The outer edge 22 illustrated in Figures 3 and 4 has a preferably uniform thickness T from the outer perimeter of the frame to its junction with the perpendicular rib 32, and provides sufficient surface area to structurally connect the window frame to the housing. aircraft, usually using screws or other suitable fastening devices.

In this way, the frame 24 thinners or decreases in diameter radially inwardly from its junction with the rib 32 to the radially internal perimeter of the frame, which defines a relatively thin arcuate lip 48 that circumscribes or circumferentially delimits the opening. central 26.

In the preferred embodiment, the outer side 30 along the frame 24 is generally parallel to the inner side 28 along the outer edge 22 in two different planes, generally planes, transversely spaced apart by the transition rib 32.

Accordingly, the inner side 28 of the sash 24 inclines radially outwardly toward the offset lower outer edge 22 to its junction with the transition rib 32 to form a slanted annular seat 50 completely surrounding the glazing 20 which has a corresponding chamfered perimeter conforming to the seat chamfer.

Thus, the differential pressure loads acting on the glazing during flight are transmitted through the beveled joint to the tapered frame 24, which frame 24 has a relatively thick arched fillet or joint with the transition rib 32 to in turn transmit the pressure loads to the surrounding outer edge with reduced voltage.

The outer edge 22, the rib 32 and the frame 24 shown in Figure 4

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6/19 provide a continuous structure loading path between the concentric outer and inner perimeters of the frame, and the common layers 1-7 extend radially therethrough and comprise high strength fibrous blades fixedly attached to a rigid resin matrix 52, illustrated schematically in Figure 4.

The different layers illustrated in Figure 4 preferably include an externally exposed outwardly facing outer layer 1 of the aircraft to the environment, a transversely opposite internally exposed innermost layer 7 facing the interior of the aircraft cabin, and various different inner or intermediate layers 2 to 6, for example, laminated and hidden by opposite inner and outer layers.

The exposed common outer layer 1 completely covers the outer face of the window frame to provide custom protection, including lightning protection.

Additional protection for the window frame can be obtained by attaching an annular erosion shield 54 to the outer side of the frame 24, as shown in Figures 2 to 4. The erosion shield is preferably sheet metal. It is thin, such as titanium, and provides a solid metal ring along shoulders 36, 38 and rails 40, 42, completely surrounding the central opening 26 to protect against erosion caused by wind and rain.

The height or depth of deviation between the frame 24 and the outer edge 22 shown in Figure 4 is chosen to correspond to the thickness of the surrounding carcass of the aircraft 14, shown in a translucent manner, so that the outer surface of the frame substantially flush with the outer surface of the aircraft body.

Correspondingly, the thin erosion shield 54 is lowered into the frame and projects with slight elevation or out of the aircraft housing by about 1 to 3 thousandths of an inch (0.02 to 0.08 mm) to provide a slightly raised relief to ensure that the erosion shield captures wind and rain erosion rather than windowpane and shell edge. The slight protrusion of the uniform erosion shield, however, provides aerodynamic flow.

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7/19 uniform ambient air 16 as it moves through the window while operating the aircraft at speed.

In addition, the erosion shield 54 shown in Figure 4 conforms to the flat outer surface of the sash and has arcuate opposing edges that combine internally on the aircraft. For example, the erosion shield 54 preferably surrounds, in part, the lip of the sash 48 to minimize or eliminate direct exposure of the underlying composite laminate to external free-flowing air 16, which may contain rain or particles that otherwise could erode the relatively more flexible composite frame.

[0036] The composite laminated window frame 18 shown in Figure 3 has specific advantages in design, strength and fabrication as well as in manufacturing cost and lifetime durability. Window frame 18 is defined by its common outer edge 22, frame 24 and transition rib 32, which may vary appropriately in size, thickness and configuration, with corresponding differences in length L, width W and curvature in different planes represented. by the annular radius R of the window frame itself, as well as the vertical curvature A of the window frame conforming to the local curvature of the aircraft tubular cabin.

The erosion shield 54 is illustrated in more detail in Figure 5. The shield is a unitary or integral component containing an annular strip 56 integrally formed with a radially outer edge 58 and a radially inner hook or clamp 60. These three components, strip 56, edge 58 and clamp 60 in their entirety define a relatively simple erosion shield 54 which is preferably formed of a unitary sheet metal, or sheet metal, of constant thickness t.

Sheet metal shield 54 is preferably formed of thin titanium, with a small thickness t of about 8 mils (0.2 mm) to be lightweight and have better strength, durability, and plastic and elastic flexibility. Band 56 forms the intermediate ring of the shield and is a flat sheet metal for its smooth inner and outer surfaces.

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Outer edge 58 forms an outwardly convex rounded edge smoothly blending with the flat strip 56, and the inner clip 60 forms another outwardly convex rounded edge smoothly blending in with the flat strip 56

Outer edge 58 provides a rounded edge or outer arc that is aerodynamically smooth on the outer side of the armor and matches the aircraft casing, and similarly the inner clamp 60 provides another smooth outer rounded edge along opposite edge of the center strip and blends smoothly with the pane.

The erosion shield 54 conforms to the exposed outer surface of the support frame 24 to which it is properly secured. The strip 56 is preferably attached to the flat surface of the frame, with the outer edge matching the strip with the surrounding outer edge 22 of the frame where it meets the outer casing 14 of the fuselage. In addition, the inner clip 60 coats or covers the lip end of the frame 24 around the central opening 26 into which the pane 20 is mounted.

[0043] The specific advantages of sheet metal erosion shielding 54 are its unitary and fully annular configuration and its thin profile with three-dimensional (3D) amplitude. These aspects enable the effective fabrication of the shield itself, advantages in mounting it with the supporting window frame, and preferential erosion protection of the underlying composite window frame when used in the application of aircraft flying at high speed in the environment.

The metal erosion shield protects the composite frame from damage and erosion caused by high-speed rain and high-speed particles charged into the air stream.

Figures 2 and 3 illustrate the predominant horizontal flow of air flow 16 during flight operation of the aircraft. Figure 5 also illustrates the predominant backward air flow 16 during operation, which moves differently through the different portions of the generally oblong aircraft window.

Therefore, the annular erosion shield 54 is preferably

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9/19 asymmetric around its circumference and around the central common opening 26 of the shield itself and the supporting window frame 18.

The erosion shield 54 initially illustrated in Figure 3 is sized and configured to match the size and configuration of the exposed laminated frame 24 of the window frame 18 to protect this frame during flight in aircraft operation. Like frame 18, corresponding components of shield 54 are similarly configured.

More specifically, the band 56, the edge 58 and the clamp 60 of the unitary shield 54 together form front and rear vertical shoulders 62, 64 spaced laterally or horizontally along the common minor axis 44 of the shield and the frame, and also they form upper and lower horizontal rails 66, 68 spaced longitudinally or vertically along the major major axis 46, yet again common to the shield and frame. The corresponding shoulders and rails of the shield 54 and the underlying frame circumferentially surround the common central aperture 26 in which the pane is mounted.

The asymmetry is preferably introduced into the annular shield 54 surrounding the central aperture 26 for both preferential erosion protection of the underlying frame and for improved aerodynamic performance, for example. More specifically, the center strip 56 is a flat or uniform sheet metal, and is flat and straight in cross section along the shield, as illustrated in more detail in Figure 5.

Similarly, the outer edge and inner clip 60 delimiting the circumference of the strip are laterally arcuate from its common inner side to form a groove or annular inner rail 70 surrounding the central opening 26. The inner rail 70 is sized and configured to match the annular profile of the frame 24 on which it is mounted.

In contrast, the opposite outer side 30 of the shield 54 is continuously uniform over the convex edge 58 and the clamp 60 and the flat central strip 56 therebetween to provide a smooth, aerodynamically exposed surface around the entire circumference of the shield. shield that is exposed

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10/19 during high-speed ambient air operation 16 shown schematically in Figure 5.

Due to the 3D configuration of the oblong window shown in Figure 5, the annular clamp 60 surrounding the central aperture 26 is preferably symmetrical on the opposite upper and lower sides of the secondary axis 44, while it is asymmetric on the front sides. and rear axles of the mainshaft 46.

Similarly, the annular strip 56 and the integral outer edge 58 are preferably symmetrical or uniformly circumferentially around the asymmetric inner clamp 60 surrounding the central aperture 26.

The convex edge 58 preferably has a uniform arc length X radially outwardly from its junction with the center strip 56, with the arc length being circumferentially uniform around the shoulders 62, 64 and the rails. 66, 68 of the entire armor. The arc length X should be sufficient to properly match the erosion shield inwards around the entire perimeter of the underlying frame 24 to prevent high-speed outside air 16 from seeping under the shield and prevent undesirable lifting forces on she.

As shown in Figure 5, the outer edge 58 blends internally below the outer surface of the fuselage surrounding outer casing 14, and the small recess or gap found between them can be filled with a suitable seal to cover the edge and continue the aerodynamically smooth surface between lane 56 and the aircraft body. The X-arc length of the edge can be up to about 90 degrees to cover the frame until it joins the frame rib 32.

[0056] Figure 5 schematically illustrates the predominant upward flow direction of airflow 16 during aircraft flight, which is generally parallel to the horizontal secondary axis 44 of the window. Since the window is annular, the local airflow direction changes relative to the window's local geometry, and specifically to the local frame geometry 24 and its protective shield 54.

[0057] Once the front and rear shoulders of the window are oriented

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11/19 vertical or generally parallel to the mainshaft 46, air flow generally flows perpendicularly over them during operation, first passing through the front shoulder and then past the rear shoulder. Thus, the outer edge 58 in the front shoulder 62 acts as the front edge of the shield, but becomes the rear edge of the shield along the rear shoulder 64.

Thus, the inner clamp 60 forms the rear edge along the front shoulder 62, but becomes the front edge along the rear shoulder 64.

Since the shield rails 66, 68 are oriented generally parallel to the secondary axis 44 in the predominant direction of air flow 16, air flow will flow similarly generally parallel along its edge and clamp portions. .

However, since the exemplary window configuration is vertically oblong and generally rectangular, its shoulders and rails are correspondingly arched, with the rails joining shoulders at arched corners around the central opening. This further complicates the high-speed relative flow of airflow along the locally curved corner portions of the frame and shield, specifically along the two rails and their shoulder joints.

Since the frame 24 shown in Figure 5 tapers radially inwardly relative to the relatively thin inner lip 48, the corresponding cross section of the erosion shield 54 complements this taper to surround the window and minimize any internal deviation of the window. from the aerodynamically uniform cast line or outer surface of the aircraft.

Thus, the inner clamp 60 preferably has smaller size and depth than the larger outer edge 58 to conform to the thin lip 48 and the tapering of the frame.

As initially shown in Figure 5, the inner clamp 60 is preferably asymmetric around the central opening 26 to accommodate the tapering in the frame 24 and the local differences in incident air flow during aircraft flight. In particular, inner clamp 60 has different transverse arc length Y, Z

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12/19 on the shoulders of the corresponding front and rear shield 62, 64, which differ to the corresponding rails 66, 68.

Since the predominant direction of air flow 16 in Figure 5 is from left to right, inner clamp 60 is preferably greater in arc length Z along the back shoulder of shield 64 than along shoulder. front of the shield 62.

Since the frame frame 24 thickens radially outwardly from its inner lip 48 to its junction with the annular rib of frame 32, the outer edge 58 of the erosion shield 54 preferably has an arc length. X is a transverse curvature or radius greater than that of the inner clamp 60 whose curvature or radius is relatively small to surround the relatively narrow frame lip 48 with the corresponding arc length Y, Z being suitably small.

For example, the inner clamp 60 may have a transverse arc length Y of about a quarter of a circle, or 90 degrees, along the length of the front shoulder 62 to define its rear edge. In addition, the same clamp 60 has a rear arc length Z of approximately one half circle, or 180 degrees, along the rear shoulder 64 which defines its front edge. The front arc length Y and the rear arc length Z remain substantially uniform or constant throughout the vertical length of the front and rear shoulders 62,64 and remain uniform in size at the corresponding front and rear portions of the two rails 66,68.

In this manner, the larger size clamp 60 along the front edge of the rear shoulder 64 can cover the narrow lip 48 of the rear shoulder to provide erosion protection on its entire surface and to prevent infiltration of ambient air flow into high speed incident between the armor and the rear shoulder. However, the inner clamp 60 defines the rear edge on the front shoulder 62 and need not be so large since the air flow does not fall directly on the rear edge but leaves a swirl of air therein.

As shown in Figure 5, inner clamp 60 is preferably small.

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13/19 along the front shoulder 62 and larger along the rear shoulder 64, and therefore increases in size or length symmetrically arched along both upper and lower shield rails 66, 68 between the front and shoulder shoulders. rear 62, 64. Along the rear edge of the front shoulder, clamp 60 has the shortest arc length Y, and along the front edge of the rear shoulder 63, clamp 60 has the largest arc length Z, with a proper transition in arc length laterally between them.

For example, the arc length of the clamp 60 may increase linearly between the two shoulders, as illustrated, or may have an abrupt increase as desired. Since the main axis 46 laterally divides the window frame and the shield into two substantially equal parts or halves, the transition length increase in arc preferably occurs along both closely adjacent or closely spaced rails 66, 68. at the intersection of the main axis with its intermediate parts, or the positions at 12 o'clock sharp and 6 o'clock sharp.

The transition in clamp size 60 shown in Figure 5 may occur at the top and bottom of the shield in a relatively small arcuate transition band K of a few degrees both forward and backward of the shield's vertical centerline. In this transition region K, free-flowing air 16 travels generally parallel along the shield and its clamp junction with the mounted pane, and begins the transition to the front edge of the rear shoulder, for which maximum protection against damage is desired. erosion.

The resulting asymmetrical configuration of the annular erosion shield 54 illustrated in Figure 5 therefore provides maximum erosion protection across all front edge regions of annular frame 24 as the front edge transitions from the edge. 58 along the front shoulder of the shield 62 to the inner clamp 60 along the rear shoulder of the shield 64, with the change in relative position of the front and rear edges occurring similarly along both rails 66, 68.

Similarly, the inner ring or rail 70 defined by the plate shield

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Arcuate metal 14/19 54 conforms to the exposed surface of the underlying tapered frame 24. The rail 70 diverges widens internally along the front shoulder of the shield 62 to cover the front shoulder of the underlying frame 36. In contrast, the rail 70 along the rear shoulder of the shield 64 converges slightly inwardly due to the larger hook clamp 60, and therefore provides a mechanical J-hook connection over the rear shoulder of the frame 38.

Figure 6 illustrates an enlarged sectional view of a portion of the integrated window frame and shield illustrated in Figure 5, with the entire erosion shield 54 being fixedly attached to the otherwise exposed surface of the frame frame 24 using a suitable adhesive 72, such as epoxy.

The thin erosion shield 54 is preferably flush mounted on the outer surface of the frame 24, which has a corresponding recessed seat 74 specially configured for it. The seat 74 can be precisely machined to the outer surface of the composite frame 24 to a suitable depth so that the combined thickness of the thin shield 54 and the underlying adhesive 72 permits flush mounting.

As indicated above, the thickness t of sheet metal shield 54 may be 8 milliseconds (0.2 mm), and therefore the depth of seat 74 is suitably greater for flush mounting of the shield using the sticker. For example, the depth d of the seat may be about 15 milliseconds (0.38 mm), with the difference in thickness being provided for the thickness of the specific adhesive used.

Seat 74 faces outwards and internally receives the inner rail of the erosion shield 54 so that the outer edge 58 remains flush with the frame 24 at its support end and the arcuate clamp 60 remains flush with the frame around the inner lip 48, and the center strip 56 provide a uniform surface with the aircraft housing.

Thus, the inner side of the erosion shield 54 defining the annular rail 70 conforms to the machined seat 74 on the outer side of the frame

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15/19 of window 24. In addition, the transversely opposite external side of the erosion shield maintains an aerodynamically uniform surface with the surrounding aircraft casing. Aerodynamic pressure losses are therefore reduced due to uniform erosion shielding protecting the underlying window frame.

The outer edge 58 of the erosion shield blends internally into the surrounding opening of the aircraft casing to prevent high velocity airflow infiltration. The corresponding gap around edge 58 may be suitably filled with a seal to provide a smooth and continuous junction with the surrounding aircraft housing.

In addition, quite significantly, the thin narrow lip 48 of the window sash 24 is protected by the exposed outer clip 60 of the larger surface-shielded shield along the front edge lip 48 of the rear shoulder of the shield 62. that along the rear edge lip 48 of the front shoulder of the shield 62.

Accordingly, the unitary sheet metal erosion shield 54 described above has a relatively simple configuration, yet still enjoys many advantages over configuration, fabrication, assembly and performance.

For example, Figure 7 schematically illustrates an exemplary method for producing or fabricating erosion shielding from an initially flat sheet metal 54M.

The initially flat sheet metal 54M is suitably cut to the required oblong configuration with sufficient material to form the corresponding portions of the final erosion shield.

An appropriate rolling forming apparatus 76 may be used to cold-roll the initially flat plate 54M in the final 3D configuration of the erosion shield. The flat plate is properly guided through the apparatus 76 in one or more passes to laminate to the desired shape the arcuate outer edge 58 and the clamp 60 forming the rail

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16/19 internal 70 required.

A cold-roll forming process suitable for forming the shield 54 may be carried out commercially by Ducommun Aero Structures of Gardena, CA.

Final erosion shield 54 is a fully annular component with increased strength and stiffness due to the bending moment of inertia created by the 3D cross-section profile of the rail. Still, the relatively narrow ring of the relatively large perimeter of the shield introduces significant elasticity into the shield, which can be used for added advantage both in mounting with the underlying window frame 18 and for differences in window curvature.

More specifically, Figure 5 also schematically illustrates a method of mounting the 3D erosion shield 54 on the underlying composite window frame 18.

Since the rear clip 60 is generally semi-circular and partially closes the rear rail 70 in a collective form of a J-hook, the assembly process can begin by simply snapping the clip 60 from the rear shoulder 64. from the shield to the complementary arched lip 48 along the corresponding rear shoulder 38 of the frame. The intrinsic flexibility of the annular erosion shield allows the rear shoulder 64 thereof to be secured or hooked along much of its extension along the rear lip 48 of the underlying frame.

Since the inner clamp 60 decreases along the semi-circular shield rails to a quarter of a circle, the assembly process can simply be completed by fitting the interior into the correct position of the divergent rail 70 around it. corresponding portions of the frame 24 first along both shield rails 66, 68 as they fit into the correct position on the corresponding frame rails 40, 42. Thereafter, the front rail 70 of the front shoulder of the shield 62 is moved downwardly in a position seated on the front shoulder of the frame 36.

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The J-shape of the rear rail 70 provides a mechanical interlock between the rear shoulder of the shield 64 and the rear shoulder of the underlying frame 38, which therefore locks the entire annular shield over the corresponding seat along of both rails 40, 42 and the front shoulder 38 of the underlying frame.

Adhesive 72 is properly applied between the shield and the frame immediately before mounting. The installed shield is therefore mechanically and adhesively connected to the underlying window frame in an integral assembly therewith.

Conversely, any attempt to disassemble the frame shield requires overcoming the cured adhesive 72 therebetween, as well as overcoming the substantial locking force created by the rear clamp 60.

In Figure 5, high-speed free-flowing air 16 flows downstream over the erosion shield during operation and passes over the underlying pane, which is preferably mounted with a small recess of about 1 to 3 thousandths. inch (0.02 to 0.08 mm), for example, within the erosion shield in the central aperture 26, as shown in Figure 6.

Since the rear clamp 60 partially surrounds the narrow lip 48, significant reaction loads prevent high-velocity airflow from infiltrating this front edge joint. In addition, the total surface cover of the rear clip 60 fully protects the front edge of the rear shoulder of the underlying frame 38.

A suitable seal or gasket may be placed between the pane and its frame seat 50, and may also be used to fill the gap between clamp 60 and the pane.

Another advantage of the 3D configuration of unitary erosion shield 54 is shown schematically in Figure 8. As indicated above, the aircraft includes corresponding rows of windows on opposite sides of the fuselage, which share the common configuration of the oblong window frame 18. Due to the variable curvature of the aircraft tubular cabin, the window frames 18 conform to the

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18/19 curvature generally indicated by radius A entered above.

However, the curvature or radius of the cabin and the corresponding windows varies between the front and rear of the aircraft, and therefore the corresponding curvature of each window frame may not only vary from window to window, but may also vary. range between the two shoulders 36, 38 in an individual window. In Figure 8, this is represented by the six radii of curvature AF which may vary by a mere fraction of one percent.

However, even this slight variation in curvature requires corresponding modifications in the configuration of the windows for the different locations in the aircraft cabin.

[0098] A single aircraft can have about ninety-two windows in seventeen different sizes and configurations, including five weights, from extra light to extra heavy. All windows will have similar oblong configurations, and all windows will use a corresponding oblong erosion shield.

However, instead of having seventeen different sized erosion shields 54 to seventeen different sized window frames, the intrinsic flexibility of the erosion shield can be advantageously used to decrease the number of different designs required for them.

[0100] For example, several window frames 18 may have different AF curves along their shoulders, requiring different size window frames 18 for them, but these different window frames may share an erosion shield 54 in size and common or identical configuration.

In particular, each of the three window frames 18 shown in Figure 8 may have an identical erosion shield 54, differing only in their corresponding curvature to conform or correspond to the different curvature AF of the three window frames.

The commonly designed erosion shield 54 can therefore simply be flexibly biased during hook mounting and snapping into the different underlying window frames to match their different curvature within the elastic flexibility of the erosion shield.

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Figure 8 schematically illustrates that the erosion shield of a design 54 may be flexibly biased along the minor axis 44 or major axis 46, or both, to match the different AF bends of the different moldings. window. Commonly designed erosion shielding therefore reduces the total number of different design parts or designs required for a specific aerodynamic application, and thus reduces the manufacturing cost.

Accordingly, the relatively simple sheet metal erosion shield 54 disclosed above easily conforms to the 3D configuration of tapered window frame 24 to provide erosion protection throughout its perimeter while maintaining an aerodynamically uniform profile. with the pane 20 mounted within the sash and the aircraft housing surrounding the sash. The shield is preferably asymmetrical to provide a mechanical interlock between the shield and the tapered frame that is effectively resistant to the aerodynamic pressure forces of the high-speed free-flowing airflow through the window during aircraft flight.

[0105] Erosion shielding is easily fabricated from a common sheet metal and laminated or stamped to the desired shape, and quickly affixed to the underlying composite window frame in an integrated assembly having increased strength and durability due to the co-operation of surface materials. high strength that make it up.

Although it has been described herein what would be considered to be preferred and exemplary embodiments of the present invention, other modifications of the invention will be apparent to those skilled in the art based on the teachings disclosed herein, and it is therefore desired to ensure in the appended claims all modifications that fit the true spirit and scope of the invention.