DUCT FOR HOT AIR

Abstract: Damage to the skin of the annular cowl (11) of the intake duct of a turbo-fan engine of an aircraft by exhaust on to it of hot air used within the cowl for de-icing its leading edge (10) is avoided by channelling spent air through an exhaust duct (15) to an exhaust aperture (21) in the surface of the cowl, and providing a heat shield (23) in the skin downstream of the exhaust aperture (21).

Description: This invention relates to a duct for conveying hot air to a selected area on the inside surface of the skin of an aerostructural leading-edge compartment of an aircraft for preventing accumulation of ice on the external leading-edge surface of the said selected area. It is known to channel hot air derived from a turbo fan engine served by an inlet cowl to a spray ring located within an annular leading edge compartment of the cowl. The hot air is sprayed from the spray ring onto the selected skin area and thence exhausts into the engine intake duct by means of an annular slot in the skin at the rear edge of the compartment. It will be appreciated that total control over the rate of supply of the hot air may not be practicable, so that there may be occasions when the air exhausting from the exhaust slot into the engine intake is still at a temperature sufficient to introduce a risk of degradation of any composite structures present in the skin immediately downstream of the exhaust slot. One object of the present invention is to obviate this hazard. In accordance with the invention, the duct comprises a delivery duct through which hot air is channelled forwardly towards the leading edge, an exhaust duct through which spent air, that is, air which has flowed over the inside skin surface, is channelled rearwardly of the compartment, from the compartment to an exhaust aperture in the aircraft skin, and a heat shield on the area of the skin immediately downstream of the aperture. Preferably the delivery and exhaust ducts are provided as a double-walled duct comprising an inner delivery duct through which the hot air flows to the spray ring, and an outer exhaust duct with the exhaust aperture in the outer skin. In such a preferred embodiment, there is an open annulus between the inner and outer duct walls at their forward ends thus allowing the spent anti-icing air to pass directly from the leading edge compartment to the duct annulus and thence overboard via the aperture in the outer skin. Preferably an annulus over-pressure indicator is provided so that a failure of the inner duct wall which allows air to pass directly to the exhaust annulus can be detected and subsequent remedial action undertaken. In the accompanying drawings, given by way of example: Figure 1 is a longitudinal, radial section through the wall of an annular inlet cowl, and through an embodiment of duct in accordance with the present invention; and Figure 2 is a perspective view of the embodiment of Figure 1. In Figure 1 there is shown a leading edge compartment 10 of the inlet cowl 11, served by a hot air delivery duct 12 to an air-dispensing spray ring 13, which ring is sealed to the duct 12 by a piston-type seal 14. Surrounding the delivery duct 12 is an exhaust duct 15 to define an annular exhaust passage 16 open at its front end 17 to the compartment 10 and sealed to a bulkhead 18 at the rear of the compartment 10 with another piston-type seal 19. Exhaust air is channelled along the passage 16 to an outlet duct 20 sealed to the outer duct 15 and to the periphery of an aperture 21 in the skin of the cowl 11, the aperture 21 being covered by a grille 22. Downstream of the aperture 21 is a heat shield 23. Within the exhaust passage 16 is a pressure sensor 24, connected to a sensor device arranged to alert cabin staff to any rise in pressure in the passage 16 consistent with rupture of the wall of the delivery duct 12. Figure 2 shows, inter alia, more detail of the aperture 21, grille 22 and heat shield 23.

Claims: 1. A duct (12) for conveying hot air to a selected area on the inside surface of the skin of an aerostructural leading-edge compartment (10) of an aircraft for preventing accumulation of ice on the external leading edge surface of the said selected area, characterised in that the duct comprises a delivery duct (12) through which hot air is channelled forwardly towards the leading edge, an exhaust duct (16) through which spent air, that is, air which has flowed over the inside skin surface, is channelled rearwardly of the compartment, from the compartment to an exhaust aperture (21) in the aircraft skin, and a heat shield (23) on the area of the skin immediately downstream of the aperture (21). 2. A duct as claimed in claim 1 characterised in that the delivery duct (12) is contained within the exhaust duct (16). 3. A duct as claimed in claim 2 characterised in that the delivery duct (12) is connected by a piston seal (14) to an air dispenser (13) within the compartment (10). 4. A duct as claimed in claim 2 or 3 characterised in that the exhaust duct (16) is sealed to a bulkhead (18) at the rear of the compartment (10) by a piston seal (19). 5. A duct as claimed in any one of the preceding claims characterised by a pressure sensor for sensing within the exhaust duct any rise of pressure indicative of rupture of the wall of the delivery duct within the exhaust duct.

Inventors: COLE, DEREK
Applicants: SHORT BROTHERS PLC
Application year: 1986
Main classification: B64D15
IPC codes: F02C7, B64D15