AU6391580A - Composite leading edge for aircraft - Google Patents

Description

COMPOSITE LEADING EDGE FOR AIRCRAFT BACKGROUND The invention relates to leading edges of aircraft sections and particularly to such leading edges which include rubber coverings such as deicer or erosion shoes or boots.

Certain sections of today's aircraft employ rubber sheet-like components along portions of their leading edges, such as deicer or erosion "shoes". These rubber components, also sometimes referred to as

"boots" or "blankets", are often attached along leading edges of aircraft sections through use of a suitable adhesive or cement disposed between the outer surface of the section leading edge portion and the inner surface of the rubber component. Actual application of the rubber component to the leading edge portion is sometimes performed in the field or may be done in the factory of the rubber component manufacturer who is furnished all or a portion of an appropriate aircraft section structure in order to apply the component.

Because selected sections of aircraft such as airfoils or nose sections, are critically contoured metal structures, great care must be exercised to assure that the contour of the leading edges of such sections remain aerodynamically suitable during applica¬ tion of the rubber component and that the adhesion between the leading edge surface and the rubber is of such uniformity and strength that the rubber component will remain secure during service conditions. Also, care must be exercised to assure that the outer surface of the applied rubber component remains as smooth as possible for aerodynamic reasons.

Despite extreme care taken in applying these rubber components to leading edges, it is common to find that aircraft sections have irregular or non- smooth rubber component surfaces at their leading edges. Also, it is possible that the rubber component can be destroyed or lost during service due to in¬ sufficient adhesion. Furthermore, it has been found that when replacement of rubber components is necessary, this operation is difficult and inefficient.

SUMMARY This invention provides a removable leading edge portion for a selected section of an aircraft which leading edge portion is a molded non-metallic composite member consisting of an inner rigid component and an outer sheet-like flexible elastomeric component. The composite is shaped and formed in a mold with the rigid component forming to substantially the leading edge contour and the elastomeric component mold bonding to the outer surface of the inner component and conforming to the proper aerodynamic contour. The outer surface of the outer rubber component forms substantially free of surface irregularities or wrinkles due to the fact that substantially all irregularities of the elastomeric component occur along the interface of its inner surface and the rigid component outer surface. These molded composites are readily installed to function as the leading edge of a selected aircraft section, are easily replaceable, provide a substantially wrinkle-free outer elastomeric surface for the leading edge, and provide an elastomeric shoe or boot which is uniformly and strongly bonded because of its being formed simultaneously with the inner component in an appropriate mold. The molded composite as applied to an aircraft section, provides a desired aerodynamic surface and an aerodynamic force load carrying member or aerodynamic force transmitting member according to the composite design and manner of attachment.

THE DRAWINGS In the drawings of this specification, the invention is illustrated with respect to several pre¬ sently preferred embodiments wherein

y > ^ Fig. 1 is a perspective view of a portion of an aircraft wing structure;

Fig. 2 is a cross-section of the wing structure of Fig. 1 taken along lines 2 - 2 of Fig. 1; Fig. 3 is a cross-sectional view similar to

Fig. 2 of a wing structure illustrating a modification; Fig. 4 is^' a perspective view of a portion of an aircraft; and

Fig. 5 is a cross-sectional view of the nose structure of the aircraft shown in Fig. 4, taken along lines 5 - 5 of Fig. 4.

DESCRIPTION In Fig. 1 of the drawings, an aircraft wing is generally referenced 10, which wing comprises a principal or main body portion 12 and a leading edge portion 14. The leading edge portion 14 is illustrated as removably secured to the wing main portion 12 by ^"a series of spaced"fasteners 16. Although not shown, the removable leading edge portion 14 is understood to extend continuously to the wing tip (also not shown) . The construction of this leading edge portion is in accordance with a presently preferred embodiment of the present invention shown in more detail in Fig. 2, or, alternatively, in Fig. 3. In Fig. 2, removable leading edge portion 14 is shown as a structural composite comprising an outer flexible sheetlike component 20 and an inner rigid component 24. Outer component 20 is preferably composed of flexible reinforced or unreinforced rubber, or rubberlike material. Inner component 24 is preferably composed of rigid nonmetaUic material such as plastic. The outer and inner components are mold bonded to each other (i.e. are united in a mold used to form the composite to the leading edge contour) . The rubber outer component 20 as shown in

Fig. 2 and in accordance with a preferred embodiment is a deicer shoe or blanket. As such, component 20 includes a plurality of chambers 22 adapted to receive fluid, such as air, from a fluid source (not shown) . Upon receipt of air into chambers 22, portions of the outer surface 26 of flexible component 20 expand or bulge such as to break up ice which may form along the leading edge portion of the wing. Deicers such as just described are generally known as pneumatic deicers. It is understood that deicer component 20 could also be an electrical type deicer wherein a rubber blanket or shoe is provided with embedded resistance coils which, when ' energized, generate heat to melt ice which may form along the leading edge of the wing. Control of deicer operation, whether pneumatic or electrical, is usually by the aircraf operator . As stated, inner component 24 is preferably of rigid plastic material and more preferably, is constructed of such plastic reinforced by glass fibers. This more preferred material, which is easily formed to selected contours by molding, manifests strength and durability in performance comparable to that of a metal leading edge. Inner component 24 is carefully formed to a preselected contour dictated by the required aero¬ dynamic shape of the structure of which it is to form part. As seen further in Fig. 2, deicer outer component 20 is of such area so as.to cover substan¬ tially all of the outer surface 27 of inner component 24. This enables a good bond to be formed along the inner surface 25 of deicer 20 and outer surface 27 of component 24 during mold forming of the composite 14. Also, as seen in Fig. 2, the marginal areas 23 of component 24 are not covered by deicer 20 and are formed slightly thicker than remaining areas so as to receive fasteners 16 securing the composite 14 to the main body 12 of the wing. It is also understood that composite 14 may be secured to the wing body 12 by means other than fasteners, such as, for example, by suitable adhesives.

In Fig. 3, an alternate design is shown wherein composite 14' secured to wing body 12' by fasteners 16' comprises a flexible rubber outer compon- ent 20' and an inner rigid plastic component 24'. The difference between composite 14' and composite 14 as shown in Fig. 2 is that outer component 20' of compos¬ ite 14' is a simple rubber sheet member which does not function as a deicer. Thus, in this case rubber com- ponent 20' functions solely as a protective covering for the leading edge area of the aircraft. These protective coverings or "erosion shoes" are often used rather than deicer blankets where ice formation is not an expected occurrence. In both Figs.2 and 3, it is noted that the composites are applied to a wing structure which is foreshortened at what is typically its leading edge section such that the inner components 24 (Fig. 2) or 24' (Fig. 3) become the force load carrying or aero- dynamic force transmitting members. It is understood, however, that composites according to the present invention may be applied in glove-like fashion over wing sections which have not been foreshortened where a leading edge portion of the wing remains integral with the wing body. This alternate form has the advantage that the force carrying and transmitting function of the rigid component of the composite is complemented by the wing proper through presence of the integral leading edge of the wing. Figs.4 and 5 illustrate another preferred environment where the present invention is applicable. Fig. 4 shows an aircraft 30 wherein the nose area 32 thereof is constructed in accordance with the present invention. Sensitive equipment such as radar equipment is often mounted within these nose portions and such nose portions commonly feature erosion shoes or blankets As seen in Fig. 5, nose portion 32 of plane 30 is a removable composite comprising an inner rigid component 44 and an outer flexible component 40 shown in the form of an erosion shoe. Erosion shoe 40 of composite 32 forming the nose portion of aircraft 30 is also composed of flexible reinforced or unreinforced rubber or rubberlike material. Inner rigid component 44 is preferably rigid plastic, and also, more preferably, fiber reinforced plastic as is the inner components 24 and 24' of leading edge composites 14 or 14". As in the embodiments previously described, inner component is carefully formed to a preselected contour in a mold along with the erosion shoe sheet to achieve strong and uniform bonding between the inner surface 45 of the erosion shoe component 40 and the outer surface 47 of inner compon¬ ent 44.

From the foregoing, it is evident that this invention has application to other aircraft sections where rubber covered leading edges are used. Thus, for example, these removable leading edge composites could be used as the leading edges of tail wings, tails, propellers or rotor blades in rotary wing type aircraft. As previously indicated, leading edge com- posites constructed in accordance with the present invention are readily molded composites. Typically these composites can be mold formed by placing within a mold cavity of required preselected aerodynamic contour the two component materials in uncured, partially cured or cured states. Specifically, a suitable sized layer or layers of rubber can be placed against the female portion of the mold, against which rubber layer is placed the fiber reinforced plastic layer in a par¬ tially cured state. A male mold member, or preferably conventional bagging techniques, can then form the composite by pressure against the female mold member, while heat introduced into the mold cures the composite within the aerodynamically contoured cavity between the mold members. Mold forming these composites in this manner has been found to provide a leading edge with well-bonded components wherein the outer rubber component is substantially smooth and wrinkle-free. This latter characteristic is believed due to phenomena occurring during the molding operation, where surface irregularities appear adsorbed along the interface between the inner surface of the outer flexible component and the outer surface of the inner rigid component.

From the foregoing specification which describes the invention in several preferred embodiments, it is evident that departures from and modifications to these embodiments can be made within the scope of the invention, which scope is to be measured by the following claims.

Claims (6)

CEAIMS

1. For use on a selected section of an aircraft, a removable leading edge portion having a predetermined aerodynamic contour and comprising a molded, non-metallic composite consisting essentially of:

(A) an inner, rigid component having an outer surface conforming substantially to said contour; and

(B) an outer, flexible, sheet-like elastomeric component having (1) an inner surface mold bonded to the outer surface of said inner component, and (2) a smooth outer surface conforming to said contour.

2. The invention defined in Claim 1 wherein said outer component is a deicer shoe.

3. The invention defined in Claim 1 wherein said outer component is an erosion shoe.

4. The invention defined in Claim 1 wherein said inner component consists essentially of fiber reinforced plastic.

5. The invention defined in Claim 4 wherein said outer component is an erosion shoe.

6. The invention defined in Claim 4 wherein said outer component is a deicer shoe.