It is an ongoing concern in the aviation industry that certain areas of aircraft remain protected from the intense heat of the hot air ducts through which exhaust gases flow from the jet engines, in particular, the spars within aerofoils, and more particularly the front spar nearest the hot air duct, which also forms part of the fuel tank boundary. In the event of a duct failure, the hot gases are directed out through vents strategically positioned within insulation material surrounding the hot air duct. The heat shield is positioned in such a way as to deflect the hot air away from the front spar.

An Airbus aircraft usually has metallic spars within its aerofoil. Heat shields are attached to the spars using fasteners, and are usually individually made to fit specific vent areas and, once fastened in place, tend to be awkward to remove. As a result, the shields also form part of the system installation for the aircraft. The systems installation includes all the equipment used to run the aircraft, such as electrical circuitry and pneumatic, hydraulic and fuel components.

Recently, there has been a tendency to make aerofoil spars of a lighter material such as carbon-reinforced plastics material. This material, however, is more prone to heat deformation than metal, and must be protected from hot gases to a greater extent.

Furthermore, drilling of holes in the material, in order for the shield to be fastened to a spar, contributes to weakening of the structure and therefore any such drilling should be minimised as much as possible.

The present invention seeks to alleviate the disadvantages of current heat shields by providing a smaller, lighter heat shield that can be easily removed, adapted to suit different vent positions, and which does not interfere with the system installation.

Accordingly, there is provided, a heat shield for deflecting hot gases away from an aerofoil spar, the heat shield comprising a shield member, a support member for detachably supporting the shield member, and means for adjustably mounting the support member on a hot air duct positioned within an aircraft aerofoil, the arrangement being such that, in use, the heat shield can be positioned between the hot air duct and a spar of the aerofoil.

Preferably, insulation is also provided between the hot air duct and the support member. The insulation is made from material able to withstand the temperature of the exhaust gases, preferably a material such as aluminium or titanium. The insulation may surround the hot air duct.

The support member may comprise a sleeve surrounding the insulator, in the form of a jubilee clip, whereby the support member is adjustably mounted on the insulator, and also constitutes the adjustable mounting means.

The shield member, preferably, has an arcuate structure that is concentric with the hot air duct. The shield member should have sufficient arc length, and should be adjustably positioned in such a way, as to ensure total deflection of all hot gases away from the front spar.

The arc length of the shield member may be sufficient so as to cross imaginary tangential lines between the hot air duct and each comer of the aerofoil spar.

Preferably still, the shield member is detachably attached to the support member by a fastener, and the shield member includes a receiving aperture through which to receive the fastener.

The present invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of an aerofoil of an aircraft; and

Figure 2 is a side expanded view of the D-nose assembly section of Figure 1, showing the hot air duct and heat shield.

Referring to the drawings, Figure 1 shows an aerofoil 1 of an aircraft, having a front spar 2 and a back spar 3. The front spar 2 is made of carbon-reinforced plastics material, or from a similarly heat-resistant material. The front spar 2 is situated at one end of the aerofoil 1, and defines a D-nose section 4 of the aerofoil. A hot air duct 5 (see Figure 2) is situated within the D-nose section 4, between the front spar 2 and the leading edge of the aerofoil 1. The hot air duct 5 must be capable of withstanding contained gases at a temperature greater than 230°C. A wall 6 of insulative material surrounds the hot air duct 5. An outer sleeve 7, in the form of a Jubilee clip surrounds the wall 6. The outer sleeve 7 has two fasteners 8 attached thereto, and protruding therefrom. The outer sleeve 7 also has a nozzle 9 formed on its surface. The nozzle 9 is situated at the end of a vent 10 running through the wall 6. A heat shield 11 is located between the hot air duct 5 and the front spar 2.

The heat shield 11 has an arcuate structure which is concentric with the hot air duct 5, and is positioned in such a way so as to deflect any hot gases, escaping from the hot air duct, in the event of fracture occurring in the wall of the hot air duct 5, via the vent 10 and the nozzle 9, away from the front spar 2. The heat shield 11 has a respective aperture 12 located at each of its ends, the apertures receiving the fasteners 8 on the outer sleeve 7 of the hot air duct 5 in order to fix the heat shield in the required position over the vent 10. The aerofoil 1 also holds the systems installation 13 of the aircraft. The systems installation 13 is located between the heat shield 11 and the front spar 2, and is thus protected from any hot air gases by the heat shield.

The heat shield 11 is made of a lightweight, heat-resistant material, preferably a material such as aluminium or titanium, and can be easily removed from the aerofoil 1 by unfastening the fasteners 8 attaching the heat shield to the outer sleeve 7 of the hot air duct 5. Furthermore, the position of the heat shield 11 can be adjusted to suit a variety of vent locations so that the front spar 2 and systems installation 13 remain protected from the hot gases. In order to place the heat shield 11 in the correct position over a given vent 10, the outer sleeve 7, in the form

of a Jubilee clip, is rotated circumferentially around the hot air duct 5 so as to align the fasteners 8 attached thereto with the receiving apertures 12 in the heat shield 11.

The heat shield 11 must have a sufficient arc length in order to provide total protection to the front spar 2, i. e. by ensuring total deflection of hot gases bleeding from the nozzle 9. This length must also take into account the need for providing deflection of hot gases that may escape out of the hot air duct 5 from somewhere other than the nozzle 9, in the unlikely case of a duct fracture. Therefore, as can be clearly seen in Figure 2, the arc length of the heat shield 11 must cross the tangential lines between the hot air duct 5 and each comer of the front spar 2.