WO2007135383A1

WO2007135383A1 - Heating system for leading edge of aircraft

Info

Publication number: WO2007135383A1
Application number: PCT/GB2007/001829
Authority: WO
Inventors: Anthony Bardwell; Maxwell Brown; Paul Nicklin
Original assignee: Gkn Aerospace Services Limited
Priority date: 2006-05-23
Filing date: 2007-05-15
Publication date: 2007-11-29
Also published as: GB0610258D0; GB2438389A

Abstract

A layered heating system for heating a leading edge component of an aircraft . The system includes a removable heating layer (20). The system also includes a layer (30) for removably adhering the heating layer to the leading edge component. A method for maintaining a leading edge component 40). The method includes removing at least a removable heating layer and applying a replacement removable heating layer.

Description

HEATING SYSTEM FOR LEADING EDGE OF AIRCRAFT

BACKGROUND OF THE INVENTION

This invention relates to a heating system for a leading edge of an aircraft. In particular, this invention relates to a heating system which is layered and which is removable from the leading edge.

Leading edge components of an aircraft such as a wing slat or propeller are generally heated to reduce the build up of ice which could interfere with the operation of the component to the detriment of the safety of the aircraft.

For example, currently most civil aircraft wing slat designs use hot gas for ice protection purposes. Such technology employs bleeding air from the engines, and ducting the bled air to the wing slat via tubes. The hot air is finally distributed to the slat nose skin via small holes in the tubes. The system is mainly suitable where the aircraft structure is fabricated of sheet metal, and can more easily withstand the temperature of the hot gasses from the engine. The slat is generally fabricated as a one-piece riveted structure in such a way as to create a pressure box for the hot gas bounded by the nose skin to the front, and a nose beam to the rear. The system is not efficient, as it cannot discriminate what part of the wing slat structure to heat up, and resultantly ice protect. Furthermore, this system of ice protection is both complicated and expensive.

The ice protection system for a leading edge component requires periodic maintenance. This usually requires removal of, a leading edge component such as a wing slat. Removal of the wing slats or other leading edge components renders the aircraft out of service during this maintenance which incurs a considerable inconvenience and loss of revenue to the aircraft operator.

Furthermore, damage to the leading edge component by impacts, particularly from vehicles servicing the aircraft at an airport, are a common occurrence. Damaged wing slats require time consuming removal, sourcing of a replacement wine slat and fitting and re-alignment of the replacement wing slat to the wing. This procedure is time consuming, again causing considerable inconvenience and loss of revenue to the aircraft operator.

This invention has been made in consideration of at least some of the problems indicated above.

SUMMARY OF THE INVENTION

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.

Aspects of the invention are defined in the accompanying claims.

According to an aspect of the invention there can be provided a layered heating system for heating a leading edge component of an aircraft. The system includes a removable heating layer. The system also includes a layer for removably adhering the heating layer to the leading edge component.

The layered form of the heating system allows it easily to conform to a curved surface of a leading edge component of an aircraft. The removability of the heating layer allows it to be easily replaced, thereby significantly reducing maintenance costs.

A dielectric layer can be provided for electrically insulating the heating layer from the leading edge component, which may be made from an electrically conductive material e.g. Titanium. The dielectric layer may be fused to the leading edge component and hence not removable. Alternatively, the adhesive layer may be located between the leading edge component and the dielectric layer, whereby the dielectric layer can be removed with the heating layer. A dielectric top layer can be provided for covering a surface of the heating layer distal the leading edge component, thereby protecting the heating layer and preventing electrical shorting of the heating layer. At least one of the dielectric layers can include polyimide.

A ground plane layer can be located between the heating layer and the dielectric top layer for sensing failures in the heating layer. The ground plane layer can include patterned carbon ink. The heating layer can include a fabric carrier and an electrically conductive medium, in the form of a heating mat. The fabric carrier can include dry glass cloth. The fabric carrier and electrically conductive medium can be infused with an adhesive. This forms a particularly robust yet cost effective construction. The adhesive may be a resin adhesive. Thus the heating layer can be constructed using a resin infusion process.

The heating layer can further include a resistance temperature detector (RTD) layer, which may be located adjacent the heating mat.

The adhesive layer can include a heat conductive dielectric for improving heat conduction between the leading edge component and the heating layer.

A backing layer can be provided, which can be peeled away to expose the adhesive layer for application of the heating layer (and other layers of the heating system) to the leading edge component.

According to another aspect of the invention there can be provided a leading edge component for an aircraft and a layered heating system as described above on an surface of the leading edge component.

According to a further aspect of the invention there can be provided an aircraft comprising a leading edge component as described above.

According to another aspect of the invention there can be provided a method for maintaining a leading edge component as described above. The method includes removing at least the removable heating layer and applying a replacement removable heating layer.

According to a further aspect of the invention there can be provided a method of installing a layered heating system as described above on a leading edge component of an aircraft. The method includes removably applying the heating layer to the leading edge component using the layer for removably adhering the heating layer to the leading edge component.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same may be carried into effect reference is now made by way of example only to the accompanying drawings in which like reference signs relate to like elements and in which:

Figure 1 shows an example of a leading edge component of an aircraft, and a heating system according to an embodiment of the invention applied to the leading edge component; Figure 2 shows an example of a heating system for a leading edge component according to an embodiment of the invention; and

Figure 3 shows another example of a heating system for a leading edge component according to an embodiment of the invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

DESCRIPTION OF PARTICULAR EMBODIMENTS

Particular embodiments will now be described by way of example only in the following with reference to the accompanying drawings.

According to an embodiments of this invention, a layered heating system can be provided for heating a leading edge component of an aircraft. The system includes a removable heating layer. An adhesive layer is provided, which can be used to removably adhere the heating layer to a surface of a leading edge component. The removability of the heating layer reduces down time and subsequent costs during maintenance, since replacement of the heating system is simplified.

Figure 1 shows an example of a leading edge component of an aircraft, and a heating system according to an embodiment of the invention.

The leading edge component includes an outer skin 40, which is supported by a structure 50. The outer skin may be constructed from, for example, titanium, which is electrically conductive. In the present example, the leading edge structure is a wing slat. In other examples, the leading edge component could be a propeller fin. During flight, air moves over the leading edge component in the general direction indicated by the arrow labelled 'A' in Figure 1.

A heating system 10 according to an embodiment of the invention is applied to the outer skin 40. In particular, the heating system is applied to an inner surface 12 of the outer skin.

As described above, and as shown in Figures 1 and 2, the heating system 10 is layered. In particular, the heating system 10 includes a heating layer 20 and an adhesive layer 30. The adhesive layer allows the heating layer to be applied to the inner surface in a convenient manner. The heating system may, for example, be provided in sheet form with an additional backing layer which can be removed before applying the heating layer 20 to the surface 12 of the leading edge component using the adhesive layer 30.

Since the heating system is thin (typical thincknesses for various layers described herein is discussed below in relation to Figure 3), it can be easily moulded to comply with the curved surfaces which are typically found in aerodynamic leading edge components.

Removal of the heating system is easily achievable according to an embodiment of this invention, since the heating layer can simply be disconnected from any electrical connections which are provided for powering the heating and/or for monitoring operations, and then pulled away from the surface 12. A replacement heating layer 20 can then be applied to the surface 12. It will be appreciated that this method of replacing a heating system 10 for a leading edge component is significantly easier than would be achievable with existing heating systems, which include, for example, a complex system of tubes for bleeding hot air from the aircraft engines on to the component.

With reference to Figure 2, it can be seen that the adhesive layer is positioned between the heating layer 20 and the outer skin 40 of the leading edge component. In some examples, the adhesive layer can include particles of a dielectric which has a good thermal conductivity, which can facilitate heat transfer from the heating layer 20 to the outer skin 40. While the adhesive layer 30 and heating layer 20 can be provided together in sheet form as described above, alternatively, they could be applied separately to the surface 12 of the outer skin 40 in separate steps. A typical thickness of the adhesive layer 30 would be 0.001" to 0.004", preferably 0.002".

Figure 3 shows in more detail the various layers of a heating system 10 according to an embodiment of this invention.

The example shown in Figure 3 includes an adhesive layer 30 and heating layer

20, which itself can include a number of different components. In this example, the heating system 10 also includes a dielectric layer 28a, which can serve to electrically insulate the heating layer 20 from the outer skin 40 which is typically constructed from a material which is electrically conductive (e.g. Titanium).

A dielectric top layer 28b can also be provided to electrically insulate and protect the heating layer 20 and its various components.

The dielectric layers 28a and 28b can comprise, for example, polyimide. A typical thickness of the dielectric layers 28a and 28b would be 0.001" to 0.004", preferably 0.002".

In the example shown in Figure 3, the adhesive layer 30 and the dielectric layer

28a may appear in reverse order. Accordingly, the dielectric layer 28a may be part of the outer skin 40, and form the surface 12. The dielectric layer 28a may be applied to the outer skin 40 by fusing at high temperatures. Ih this example, the adhesive layer 30 would be adjacent the heating layer 20.

As shown in Figure 3, the heating layer can include a number of different components. The heating layer 20 can achieve heating by feeding an electrical current through a resistive material to create Joule heating.

In the present example, the heating layer includes a fabric carrier layer 24, for carrying an electrically resistive material (for example a metal). During manufacture, the metal can, for example, be sprayed onto the fabric carrier layer 24. The fabric carrier layer may, for example, comprise dry glass cloth. A typical thickness of the fabric canier layer would be 0.010" to 0.030", preferably 0.014".

The heating layer can also include a resistance temperature detector (RTD) 26. In accordance with an embodiment of this invention, the RTD is provided in layered form and is located adjacent the fabric carrier layer 24. By measuring the resistance of the RTD layer, the temperature and heat output of the heating layer 20 can be monitored. The heating layer 20 can also include an adhesive or resin which can be used to bond together the various components such as the RTD layer 26 and the fabric carrier layer 24. In the example shown in Figure 3, the heating layer 20 includes two adhesive/resin layers 22. The adhesive/resin layers may comprise, for example, polyethylene, PDI or PETE.

Ih accordance with an embodiment of this invention, a resin/adhesive infusion process can be used to fuse together the adhesive/resin 22, the fabric carrier layer 24 and the resistive material included therein, and the RTD layer 26. This forms a particularly cost effective and robust construction, which can be easily used to produce a heating system which can cover a large surface area. Prior to infusion, a typical thickness of the resin/adhesive layers 22 would be 0.001" to 0.004", preferably 0.002".

In the example shown in Figure 3, the heating system 10 further includes a ground plane layer 29, which can be provided beneath the top dielectric layer 28b. The ground plane layer can comprise, for example, patterned carbon ink. The pattern can take many forms, for example a series of lines running across the heating layer 20.

The ground plane 29 can be used to for monitoring the integrity of the heating layer by checking for earth leakage from the heating layer 20. Accordingly, the ground plane layer can be used to determine a failure in the heating system, whereby appropriate replacement of the heating layer 20 can take place.

Accordingly there has been described a layered heating system for heating a leading edge component of an aircraft. The system includes a removable heating layer. The system also includes a layer for removably adhering the heating layer to the leading edge component. There has also been described a method for maintaining a leading edge component. The method includes removing at least a removable heating layer and applying a replacement removable heating layer.

Claims

1. A layered heating system for heating a leading edge component of an aircraft, the system comprising: a removable heating layer; and a layer for removably adhering the heating layer to the leading edge component.

2. The layered heating system of claim 1 comprising a dielectric layer for electrically insulating the heating layer from the leading edge component.

3. The layered heating system of claim 1 or claim 2, comprising a dielectric top layer for covering a surface of the heating layer distal the leading edge component.

4. The layered heating system of claim 3, comprising a ground plane layer located between the heating layer and the dielectric top layer for sensing failures in the heating layer.

5. The layered heating system of claim 4, wherein the ground plane layer comprises patterned carbon ink.

6. The layered heating system of any of claims 2 to 5, wherein at least one of the dielectric layers comprises polyimide.

7. The layered heating system of any preceding claim, wherein the heating layer comprises a fabric carrier and an electrically conductive medium.

8. The layered heating system of claim 7, wherein the fabric carrier comprises dry glass cloth.

9. The layered heating system of claim 7 or claim 8, wherein the fabric carrier and electrically conductive medium are infused with an adhesive.

10. The layered heating system of claim 9, wherein the fabric carrier and electrically conductive medium are infused with a resin adhesive.

11. The layered heating system of any of claims 7 to 10, wherein the heating layer further comprises a resistance temperature detector (RTD) layer.

12. The layered heating system of any preceding claim, wherein the adhesive layer includes a heat conductive dielectric for improving heat conduction between the leading edge component and the heating layer. *

13. The layered heating system of any preceding claim comprising a backing layer, wherein the backing layer can be peeled away to expose the adhesive layer for application of the heating layer to the leading edge component.

14. A leading edge component for an aircraft and a layered heating system according to any preceding claim on an surface of the leading edge component.

15. An aircraft comprising a leading edge component according to claim 14.

16. A method for maintaining a leading edge component according to claim 14, the method comprising removing at least the removable heating layer and applying a replacement removable heating layer.

17. A method of installing a layered heating system according to any of claims 1 to 13 on a leading edge component of an aircraft, the method comprising: removably applying the heating layer to the leading edge component using the layer for removably adhering the heating layer to the leading edge component.

18. method for maintaining a leading edge component, substantially as hereinbefore described with reference to the accompanying drawings.

19. A method of installing a layered heating system, substantially as hereinbefore described with reference to the accompanying drawings.

20. A layered heating system, substantially as hereinbefore described with reference to the accompanying drawings.