Venting a space to relieve pressure generated by an explosion

Abstract: An arrangement for venting to atmosphere an enclosure such as an aircraft fuselage (16) to relieve destructive internal pressure generated by an explosion within said enclosure. The arrangement includes pressure venting means (20, 21, 23) to vent an exterior boundary, eg: fuselage skin (11), of said enclosure and explosion sensitive sensor means (18) located within the enclosure whereby, in response to an explosion within the enclosure, said sensor means (18) will send a signal to the pressure venting means (20, 21, 23) and cause same to create a pressure relieving vent in said exterior boundary (11) in advance of build up of destructive internal pressure within the enclosure (16).

Description: This invention relates to an arrangement for venting an enclosed space to relieve pressure generated by an explosion. More particularly, it relates to an arrangement for venting an aircraft fuselage, in response to an explosion in a freight container stowed within the fuselage. The object of the present invention is to provide means for venting an enclosed space, such as an aircraft fuselage, in advance of a destructive pressure build up arising from an on-board explosion whereby the risk of catastrophic structural failure is minimised. It is known from CH-A-335447 to vent to atmosphere to relieve explosive pressure a fuel tank mounted within an aircraft wing by means of an explosive charge to blow a hole in the wing skin in response to an explosion sensed within the fuel tank. An arrangement according to the preamble of claim 1 is known from this document. One obvious method of relieving excessive pressure arising from such an explosion is by providing "blow-out" panels in the fuselage skin, these panels being designed to be significantly weaker than the remainder of the fuselage. A problem with the "blow-out" panel concept is that in order to demonstrate the structural airworthiness of the aircraft, it is necessary to show that the fuselage, including any such "blow-out" panels, is capable of withstanding twice the maximum cabin pressure differential. Hence, for the simple blow-out concept to work, the greater part of the fuselage would have to be designed to withstand in excess of 2 Δ P, which would constitute an unacceptable weight penalty. If however, it were possible to weaken one or more pre-designated areas of a "normal" fuselage, that is one designed to meet standard airworthiness requirements, in the time interval between the initiation of an explosion and the development of an excessive and catastrophic pressure build-up at the fuselage skin, so that the weakened areas acted effectively as blow-out panels, the probability of the aeroplane surviving the explosion would be greatly increased. An arrangement for venting to atmosphere part of an aircraft to relieve destructive internal pressure generated by an explosion within said aircraft, said arrangement including pressure venting means to vent a skin of said aircraft and explosion sensitive sensor means characterised in that the part of the aircraft is a fuselage thereof including freight container carrying means and the explosion sensitive sensor means is included in a freight container carried thereby within the fuselage whereby, in response to an explosion within said freight container, said sensor means will send a signal to the pressure venting means and cause same to create a pressure relieving vent in said fuselage skin in advance of build up of destructive internal pressure within the fuselage. Said pressure venting means may include a linear explosive charge attached to an inner surface of said exterior boundary and explosive charge detonating means, said detonating means connected by signal transmitting means to said sensor. Said linear explosive charge may be of chevron cutting cord and may be mounted in contact with said boundary surface and define a boundary of a vent area. Said explosion sensitive sensor means may be responsive to physical characteristics arising from the explosion in advance of pressure wave generation whereby excessive and injurious pressures within said enclosure are obviated. Said pressure venting means may be mounted upon or adjacent an inner surface of a fuselage skin. One embodiment of the present invention will now be described, by way of example only, and with reference to the following drawings in which:- Figure 1 illustrates a typical cross section through an aircraft fuselage incorporating one arrangement of the present invention. Figure 2 is a view in direction of arrow '2' in Figure 1 illustrating one typical pressure venting panel arrangement of the present invention. Figure 3 is a localised section through the fuselage outer skin taken along a line '3-3' in Figure 2. Referring to the drawings, Figure 1 illustrates a typical cross-section through an aircraft fuselage comprising a fuselage frame 10 supporting an outer skin 11. A floor panel 12 seats upon a floor beam 13. The lower part of the frame 10 includes an horizontal portion 14 incorporating a freight floor 15. The freight floor includes, but is not illustrated here, means for transporting and locating freight containers along the length of a freight bay 16. One typical freight container 17 is shown by way of example. Sensor means in the form of an explosion sensor 18, in this embodiment located in one wall of the freight container 17 is connected by a signal transmitting line 19 to pressure vent actuating means in the form of detonating means 20 which in turn includes a transmitting line 21 to pressure venting means in the form of a circuit 22 of explosive cord 23 defining the boundary of an effective blow out panel 24. It should be noted that the blow-out panel 24 is of a pre-determined area and location within the fuselage and multiple areas may be allocated dependent upon requirements. It should also be noted, as previously discussed, that the skin panel thickness in that vicinity, is consistent with the remainder of the fuselage. Referring to Figure 3, the explosive 23 is of the well-known 'chevron' cutting type cord seated in contact with the inner skin surface and supported within a rubber or like material moulding and located to the skin by suitable attachments 25. The chevron cutting cord 23, being a line charge when activated, as will be later described, will impose a cutting forced on the skin enabling the blow-out panel 24 to separate from the surrounding skin effectively relieving excess pressure arising from an explosion in the freight container. For the purpose of this embodiment the seat of the explosion is deemed to be at location 26. Since electrons travel more quickly than pressure waves an essential feature of the present invention is that the cutting cord detonation and thus the formation of the blow-out panel is initialised ahead of the pressure wave by an electronic signal from as close as possible to the source of the pressure wave. Thus the location of the sensor 18 is in the wall of the container, although other locations external to the container may be equally effective. To ensure this advanced initiation the sensor 18 will preferably be one sensitive to heat or light in preference to one which is pressure sensitive. This will ensure that the detector generates a signal adequately ahead of any catastrophic build-up in pressure. The present embodiment is specifically related to an occurrence within a freight container since this is the most likely situation.

Claims: An arrangement for venting to atmosphere part of an aircraft (16) to relieve destructive internal pressure generated by an explosion within said aircraft, said arrangement including pressure venting means (20,21,23) to vent a skin (11) of said aircraft and explosion sensitive sensor means (18) characterised in that the part of the aircraft is a fuselage (16) thereof including freight container carrying means and the explosion sensitive sensor means (18) is included in a freight container (12) carried thereby within the fuselage (16) whereby, in response to an explosion within said freight container, said sensor means (18) will send a signal to the pressure venting means (20,21,23) and cause same to create a pressure relieving vent in said fuselage skin (11) in advance of build up of destructive internal pressure within the fuselage (16). An arrangement according to claim 1 in which said pressure venting means includes a linear explosive charge (23) attached to an inner surface of said skin (11) and explosive charge detonating means (20), said detonating means (20) connected by signal transmitting means (19) to said sensor (18). An arrangement according to claim 2 in which said linear explosive charge (23) is of chevron cutting cord and is mounted in contact with the skin (11) and defines a boundary of a vent area. An arrangement according to claim 1,2 or 3 in which said explosion sensitive sensor means (18) is responsive to physical characteristics arising from the explosion in advance of pressure wave generation whereby excessive and injurious pressures within the fuselage (16) are obviated.

Inventors: FRAY JOSEPH BRITISH AEROSPACE, FRAY, JOSEPH, BRITISH AEROSPACE REG.AIRCRAFT LTD.
Applicants: BRITISH AEROSPACE, BRITISH AEROSPACE PUBLIC LIMITED COMPANY
Application year: 1992
Main classification: B64D45
IPC codes: B64C25, B64D45, B64C1