Duct means for aircraft

DETAILED DESCRIPTION I claim: 1.
An aircraft having propulsive fluid outlet means and in which fluid is required to be ducted from a source of pressurized fluid to another part of said aircraft to be exhausted to provide a propulsion force, including elongate duct means having spaced inlet and outlet means, said inlet means being in flow communication with said source of pressurized fluid, and said outlet means being in flow communication with said propulsive fluid outlet means, said duct means including a relatively flexible imperforate panel element biased such that on introduction of pressurized fluid into said duct, said duct is caused to expand from a non-fluid conducting condition in which said panel element together with adjacent external surface regions of said aircraft defines a substantially continuous surface and a fluid conducting condition of relatively large cross-sectional area in which said panel element protrudes from the aircraft surface.
2.
An aircraft according to claim 1, wherein tension means are associated with at least one edge region of said flexible panel member said tension means being biassed to draw the flexible panel member to its non fluid-conducting condition, the bias of the tension means being selected so that when a predetermined fluid pressure is supplied to a said duct means, the bias of the tension means is overcome to allow the flexible panel member to be inflated to its fluid-conducting condition.
3.
An aircraft according to claim 2, wherein said tension means comprise at least one relatively rigid side panel member attached to a region of said aircraft for biassed hinging movement, so as to cause said flexible panel member to be drawn to its non fluid-conducting condition.
4.
An aircraft according to claim 3, wherein two of said relatively rigid side panel members are provided, each biassedly hinged to said aircraft body and each being associated with a respective opposed side region of said flexible panel member and arranged to draw the flexible panel member to its non fluid-conducting condition when there is little or no fluid supplied to said duct means