Aircraft window erosion shield

(54) Title: PROTECTIVE SHIELDING FOR WINDOWS (57) Abstract: DE AIRCRAFT.

(30) Unionist Priority: 12/01/2007 US60 / 880,100 (73) Holder (s): The Nordam Group, INC.

(72) Inventor (s): Kevin Steven Jackson, STEPHEN FREDERICK JOSEPH WALLACE, Scott Ernest Ostrem (74) Attorney (s): Alexandre Ferreira (86) International Application: pct US2008000307 of 01/09/2008 (87) International Publication: wo 2009 / 008903de 15/01/2009

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PROTECTIVE SHIELDING FOR AIRCRAFT WINDOW

TECHNICAL FIELD

The present invention relates, in general, 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 along the body of the aircraft.

Each window includes a frame properly 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 high-strength metal, such as aluminum, and the typical window frame is also made of high-strength metal. Therefore, several metal fabrication methods are used to manufacture the individual window assemblies for the different size and strength requirements, depending on the specific window location along the aircraft body.

The weight of the aircraft directly affects the efficiency of the aircraft during flight, and therefore aircraft are continually being developed to reduce the weight and at the same time provide sufficient strength for the various components of the aircraft to enjoy a long service life during operation. commercial.

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

Therefore, it is desired to offer a light composite aircraft window frame, and a protective shield for this.

DISCLOSURE OF THE INVENTION

It is an erosion shield for an aircraft window, which includes an annular band having a radially external edge and a radially internal clamp. The shield is dimensioned to cover a composite window frame having an outer edge and an inner frame around a central opening to receive a pane. The clamp 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 the preferred and exemplary embodiments, together with its additional objectives and advantages, is described more particularly in the following detailed description, considered together with the accompanying drawings, in which:

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

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

Figure 3 is an isometric view, partly in section, of the example window shown in Figure 2, separate from the aircraft.

Figure 4 is an enlarged cross-sectional view of part of the window shown in Figure 3 and along line 4-4.

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

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

Figure 7 is a schematic view of a method for forming by cold rolling a flat sheet metal ring in the unitary anti-erosion shield 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 with different curvature.

MODE (S) FOR CARRYING OUT THE INVENTION

Figure 1 illustrates an example of a plane or aircraft 10 powered by in-flight gas turboprop engines. 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's cockpit to just before the rear tail.

The windows maintain the cabin's pressure integrity and protect passengers inside the cabin from the outside environment, including the rapid flow of outside air 16 that passes over the outside frame during the aircraft's flight.

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

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

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

The composite frame 18 is illustrated in more detail in an exemplary embodiment in Figures 3 and 4. The frame includes a radially external annular flange or edge 22 and a radially internal annular flange or frame 24 surrounding a central opening 26 which is closed in a sealed manner through the pane 20 mounted on it.

The frame 24 is offset transversely from the outer edge 22 along its thickness T in common laminations along that thickness. The laminated outer edge and the frame include several blades or layers, 1 to 7 for example, which extend laterally or radially through it along the radial geometric axis R of the frame.

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

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 can be mounted. The frame 24, or frame bar, defines an annular mullion in which the pane 20 can be mounted and secured, and resists the differential pressure exerted on the window from the aircraft's pressurized cabin.

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

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

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

The two rails 40, 42 are spaced longitudinally or vertically along a major major axis 46 of the frame and define the height or length L of the frame.

The two side shoulders 36, 38 laterally connect the central opening 26, and the two rails 40, 42 provide an upper head and a lower sill 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 shown 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 aircraft frame, usually using screws or other suitable fastening devices.

In this way, the frame 24 tapers or decreases in diameter radially inward from its junction with the rib 32 to the radially internal perimeter of the frame, which defines a relatively thin arched lip 48 that surrounds or circumferentially delimits the central opening 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 flat, spaced transversely by the transition rib 32.

Consequently, the inner side 28 of the frame 24 tilts radially outwards towards the lower outer edge deviated 22 until it joins with the transition rib 32 to form a sloped annular seat 50 completely surrounding the pane 20, which has a beveled perimeter corresponding to the seat chamfer.

In this way, the differential pressure loads acting on the pane during the flight are transmitted, through the chamfered joint, to the tapered frame 24, frame 24 which has a relatively thick fillet or arcuate junction with the transition rib 32 to, for example, in turn, transmit the pressure loads to the surrounding outer edge with reduced tension.

The outer edge 22, the rib 32 and the frame 24 illustrated in Figure 4 provide a continuous structure loading path between the concentric outer and inner perimeters of the frame, and the common layers 1-7 extend radially through it and comprise fibrous sheets of high strength fixed together in a rigid resin matrix 52, illustrated schematically in Figure 4.

The different layers illustrated in Figure 4 preferably include an externally exposed outer layer 1 facing outward from the aircraft to the environment, an internally exposed opposite transversely inner layer 7 facing inwardly in the aircraft cabin, and several internal layers or different intermediates 2 to 6, for example, laminated and hidden by the opposite inner and outer layers.

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

Additional protection for the window frame can be obtained by attaching an annular erosion shield 54 to the outside of the frame 24, as shown in Figures a 4. The erosion shield is preferably thin sheet metal, such as titanium, and provides a continuous 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 the deviation between the frame 24 and the outer edge 22 shown in Figure 4 is chosen to correspond to the thickness of the aircraft's surrounding frame 14, illustrated translucently, so that the outer surface of the frame is substantially level with the outer surface of the aircraft body.

Correspondingly, the thin erosion shield 54 is lowered into the frame and protrudes slightly or out of the aircraft body by about 1 to thousandths of an inch (0.02 to 0.08 mm) to provide a slightly raised relief raised to ensure that the erosion shield captures erosion from wind and rain instead of the window pane and edge of the hood. The slight protrusion of the uniform erosion shield, however, provides a uniform aerodynamic flow of ambient air 16 as it circulates through the window during the aircraft's operation under speed.

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

The composite laminated window frame 18 shown in Figure 3 has specific advantages in terms of design, strength and manufacture, as well as in the cost of manufacture and durability of the service life. The window frame 18 is defined by its common outer edge 22, frame 24 and transition rib 32, which can vary accordingly 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 in 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 one-piece component containing an annular band 56 formed integrally with a radially external edge 58 and a radially internal hook or clamp 60. These three components, strip 56, edge 58 and clamp 60 define, in their entirety, a relatively simple erosion shield 54 that is preferably formed of a single metal plate, or metal plate, with a constant thickness t.

The sheet metal shield 54 is preferably formed of thin titanium, with a small thickness t of about 8 thousandths of an inch (0.2 mm) to be light and have better resistance, durability, and plastic and elastic flexibility.

Band 56 forms the intermediate ring of the shield and is a flat metal plate for its smooth internal and external surfaces.

The outer edge 58 forms a rounded convex edge seen from the outside combining smoothly with the flat band 56, and the inner clamp 60 forms another rounded convex edge seen from the outside also smoothly combining with the flat band 56.

The outer edge 58 provides a rounded edge or outer arc that is aerodynamically smooth on the outer side of the shield and combines with the aircraft housing, and similarly, the inner clip 60 provides another smooth outer rounded edge along the opposite edge the central strip and blends smoothly with the window.

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

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

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

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

Therefore, the annular erosion shield 54 is preferably asymmetrical 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 that frame during flight in the aircraft's operation. Like the frame 18, the corresponding components of the shield 54 are configured in a similar manner.

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

Asymmetry is preferably introduced in the annular shield 54 surrounding the central opening 26 both for preferential protection against erosion of the underlying frame and for better aerodynamic performance, for example. More specifically, the central strip 56 is a flat or uniform metal plate, and is flat and straight in the cross section along the shield, as illustrated in more detail in Figure 5.

Similarly, the outer edge and inner clamp 60 that delimit the circumference of the strip are laterally arched from its common inner side to form a groove or annular inner rail 70 surrounding the central opening 26. The inner rail 70 is dimensioned and configured to correspond to the ring 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 between them to provide an aerodynamically uniform and smooth exposed surface around the entire circumference of the shield that is exposed during high-speed ambient air operation 16 illustrated schematically in Figure 5.

Due to the 3D configuration of the oblong window illustrated in Figure 5, the annular clamp 60 that surrounds the central opening 26 is preferably symmetrical on the opposite upper and lower sides of the secondary axis 44, while it is asymmetrical on the opposite front and rear sides main axis 46.

Similarly, the annular band 56 and the integral outer edge 58 are preferably symmetrical or uniform circumferentially around the asymmetric inner clamp 60 that surrounds the central opening 26.

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

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

Figure 5 schematically illustrates the predominant upward flow direction of the air flow 16 during the flight of the aircraft, which is generally parallel to the horizontal secondary axis 44 of the window. Once the window is annular, the local direction of the air flow changes in relation to the local geometry of the window, and specifically to the local geometry of the frame 24 and its protective shield 54.

Since the front and rear shoulders of the window are oriented vertically or generally parallel to the main axis 46, airflow generally flows perpendicularly over them during operation, first passing through the front shoulder and then passing through the rear shoulder. Therefore, the outer edge 58 on 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 clip 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 the air flow 16, the air flow will flow similarly generally parallel along its edge and clamp parts.

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

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

Therefore, the internal clamp 60 preferably has a smaller size and depth than the larger outer edge 58 to conform with the thin lip 48 and the taper of the frame.

As initially shown in Figure 5, the internal clamp 60 is preferably asymmetrical around the central opening 26 to accommodate the taper in the frame 24 and the local differences in the incident air flow during the flight of the aircraft. In particular, the internal clamp 60 has a different transverse arc length Y, Z on the corresponding front and rear shield shoulders 62, 64, differences that pass to the corresponding rails 66, 68.

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

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

For example, the inner clip 60 may have a transverse Y arc length 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 a semi-circle, or 180 degrees, along the rear shoulder 64 that defines its front edge. The front arc length Y and 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 on the corresponding front and rear of the two rails 66, 68.

In this way, the oversized clamp 60 along the front edge of the rear shoulder 64 can cover the narrow lip 48 of the rear shoulder to provide protection against erosion over its entire surface and prevent the infiltration of ambient air flow at high incident speed. between the armor and the rear shoulder. However, the inner clip 60 defines the rear edge on the front shoulder 62 and does not have to be so large, since the air flow does not fall directly on the rear edge, but leaves a whirlwind in it.

As shown in Figure 5, the internal clamp 60 is preferably small along the front shoulder 62 and larger along the rear shoulder 64, and therefore increases in size or arched length symmetrically along both the upper and lower shield rails 66, 68 between the shoulders of the front and rear armor 62, 64. Along the rear edge of the front shoulder, clamp 60 has the shortest Y arc length, and along the front edge of the rear shoulder 63, clamp 60 has the longest Z arc length, with a suitable transition in the length of arc laterally between them.

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

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

The asymmetric configuration resulting from the annular erosion shield 54 illustrated in Figure 5, therefore, provides maximum protection against erosion along all the front edge regions of the annular frame 24, since the front edge transitions from the outer edge 58 to the 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 the relative position of the front and rear edges occurring in a similar way along both rails 66, 68.

Similarly, the inner ring or rail 70 defined by the arcuate sheet metal shield 54 conforms to the exposed surface of the underlying tapered frame 24. The divergent rail 70 extends internally along the front shoulder of the shield 62 to cover the front shoulder of the frame underlying 36. In contrast, the rail 70 along the rear shoulder of the shield 64 converges slightly inward due to the larger hook-shaped clamp 60, and therefore provides a mechanical J-hook connection on the rear shoulder of the frame 38.

Figure 6 illustrates an enlarged cross-sectional view of part of the integrated window frame and shield shown 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 on the outer surface of the composite frame 24 to an appropriate depth so that the combined thickness of the thin shield 54 and the underlying adhesive 72 allows flush mounting.

As indicated above, the thickness t of the sheet metal shield 54 can be 8 thousandths of an inch (0.2 mm), and therefore the depth of seat 74 is suitably greater for flush mounting the shield using the adhesive. For example, the depth d of the seat can be about 15 thousandths of an inch (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 arched clamp 60 remains flush with the frame around the inner lip 48, and the central strip 56 provides a uniform surface with the aircraft body.

In this way, the inner side of the erosion shield 54 that defines the annular rail 70 conforms to the machined seat 74 on the outer side of the window frame 24. In addition, the transversely opposite outer side of the erosion shield maintains a streamlined surface uniform with the aircraft's surrounding housing. Losses of aerodynamic pressure are therefore reduced due to uniform erosion shielding protecting the underlying window frame.

The outer edge 58 of the erosion shield is internally combined in the surrounding opening of the aircraft body to prevent infiltration of the high-speed airflow. The corresponding gap around the edge 58 can be adequately filled with a seal to provide a smooth and continuous junction with the aircraft's surrounding housing.

In addition, quite significantly, the thin narrow lip 48 of the window frame 24 is protected by the exposed outer clamp 60 of the shield with greater surface coverage along the lip of the front edge 48 of the rear shoulder of the shield 62 than along of the rear edge lip 48 of the front shoulder of the shield 62.

Therefore, the unitary sheet metal erosion shielding 54 described above has a relatively simple configuration, but still enjoys many advantages in terms of configuration, fabrication, assembly and performance.

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

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

A suitable laminating forming apparatus 76 can be used to plastically laminate the initially flat 54M sheet 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 the arched outer edge 58 and the clamp 60 to the desired shape, forming the necessary inner rail 70.

A cold rolling forming process suitable to form the shield 54 can be carried out commercially by Ducommun Aero Structures of Gardena, CA.

The 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-sectional profile of the rail. Still, the relatively narrow ring of the relatively large perimeter of the shield introduces significant elastic flexibility to the shield, which can be used for additional advantage both in the assembly with the underlying window frame 18 and for differences in the curvature of the window.

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 clamp 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 hooking the clamp 60 from the rear shoulder 64 of 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 attached or hooked along a large part of its extension close to the rear lip 48 of the underlying frame.

Since the internal clamp 60 decreases in size along the tracks of the semi-circular shield to a quarter of a circle, the assembly process can be completed simply by fitting the divergent rail 70 into the correct position around the corresponding parts of the frame 24 firstly along both shield rails 66, 68 as they fit in the correct position on the corresponding rails of the frame 40, 42. Then, the front track 70 of the front shoulder of the shield 62 is fitted with a downward motion in its seated position on the front shoulder of the frame 36.

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 both rails 40, 42 and the front shoulder 38 of the underlying frame.

The adhesive 72 is applied properly between the shield and the frame immediately before its assembly. The nisiaiauci shield is therefore connected both mechanically and adhesive to the underlying window frame in an integral assembly with it.

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

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

Since the rear clamp 60 partially surrounds the narrow lip 48, significant reaction loads prevent high-speed airflow from infiltrating that front edge gasket. In addition, the full surface coverage of the rear clip 60 fully protects the front edge of the rear shoulder of the underlying frame 38.

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

Another advantage of the 3D unit erosion shield configuration 54 is illustrated schematically in Figure 8. As indicated above, the aircraft includes rows of corresponding windows on opposite sides of the fuselage, which share the common configuration of the oblong window frame 18. Due to the curvature variable in the aircraft's tubular cabin, the window frames 18 conform to the curvature indicated in general by the radius A introduced 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 can vary not only from window to window, but can also vary between two shoulders 36, 38 in an individual window. In Figure 8, this is represented by the six radii of curvature AF which can vary by a mere fraction of one percent.

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

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

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 of common size and configuration or identical.

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

The erosion shield of common design 54 can therefore simply undergo elastic flexing during the hooking and fitting assembly on the different underlying window frames to match its different curvature within the elastic flexibility of the erosion shield.

Figure 8 illustrates schematically that the erosion shield of a design 54 can undergo elastic bending along the secondary axis 44 or the main axis 46, or both, to correspond to the different AF curvatures of the different window frames. Erosion shielding of common design, therefore, reduces the total number of different design parts or designs required for a specific aerodynamic application, and this consequently reduces the manufacturing cost.

Thus, the relatively simple sheet metal erosion shield 54 revealed above easily conforms to the 3D configuration of the tapered window frame 24 to provide protection against erosion throughout its perimeter and at the same time maintain an aerodynamically uniform profile with the pane. 20 mounted inside the frame and the aircraft frame surrounding the frame. 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 free-flowing air flow at high speed passing through the window during the aircraft's flight.

The erosion shield is easily manufactured 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 set having greater strength and durability due to the cooperation of the high strength materials that compose it.

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