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A flow discharge device, such as a bleed assembly in a gas turbine engine, comprises a discharge outlet member having a skirt which is accommodated telescopically in a housing so as to be displaceable with respect to wall of a duct from a retracted position in which slots in the skirt lie outside th

A flow discharge device, such as a bleed assembly in a gas turbine engine, comprises a discharge outlet member having a skirt which is accommodated telescopically in a housing so as to be displaceable with respect to wall of a duct from a retracted position in which slots in the skirt lie outside the duct, and an extended position in which the slots open into the duct for the discharge of a secondary fluid into the flow in the duct. The discharge outlet member is moved to the extended position by the pressure of the secondary fluid acting on a silencer element. A spring returns the discharge outlet member to the retracted position when the flow of the secondary fluid is terminated.

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1. A gas turbine engine provided with a flow discharge device comprising a compressor bleed assembly for discharging flow into a bypass duct of the gas turbine engine, the device comprising: a discharge outlet member having at least one discharge aperture,the discharge outlet member being mounted di

1. A gas turbine engine provided with a flow discharge device comprising a compressor bleed assembly for discharging flow into a bypass duct of the gas turbine engine, the device comprising: a discharge outlet member having at least one discharge aperture,the discharge outlet member being mounted displaceably in a housing secured with respect to the wall of the duct,the housing having a valve located separate from the discharge aperture which is openable to provide communication between the interior of the discharge outlet member and a secondary fluid source and where further the discharge outlet member is displaceable by the pressure of a secondary fluid in the secondary fluid source from a retracted position in which the discharge aperture is situated outside the duct, to an extended position in which the discharge aperture is situated within the duct, whereby the secondary fluid flow is discharged through the aperture into a main fluid flow travelling along the duct. 2. A gas turbine engine as claimed in claim 1, in which the discharge outlet member comprises an end wall, and a skirt which extends from the end wall and telescopically engages the housing. 3. A gas turbine engine as claimed in claim 2, in which the end wall is provided with an acoustic liner. 4. A gas turbine engine as claimed in claim 2, in which the or each discharge aperture is provided in the skirt. 5. A gas turbine engine as claimed in claim 4, in which the discharge aperture is one of an array of discharge apertures provided in the skirt. 6. A gas turbine engine as claimed in claim 4, in which the discharge aperture, or at least one of the discharge apertures, comprises a slot. 7. A gas turbine engine as claimed in claim 2, in which a silencer element is disposed in the skirt at a position away from the end wall, the secondary fluid acting on the silencer element to displace the outlet member to the extended position. 8. A gas turbine engine as claimed in claim 1, in which return means is provided for returning the discharge outlet member to the retracted position when the discharge outlet member is isolated from the secondary fluid source. 9. A gas turbine engine as claimed in claim 8, in which the return means comprises resilient means. 10. A gas turbine engine as claimed in claim 9, in which the resilient means comprises a spring acting between the silencer element and an abutment which is secured with respect to the housing. 11. A gas turbine engine as claimed in claim 8, in which a damping means is provided for damping displacement of the discharge outlet member towards at least one of the retracted and extended positions. 12. A flow discharge device for discharging flow into a duct, the device comprising: a discharge outlet member having at least one discharge aperture, the discharge outlet member being displaceable by a pressure of a secondary fluid in a secondary fluid source from a retracted position in which the discharge aperture is situated outside the duct, to an extended position in which the discharge aperture is situated within the duct, whereby the secondary fluid flow is discharged through the aperture into a main fluid flow travelling along the duct,the discharge outlet member being mounted displaceably in a housing secured with respect to the wall of the duct, andthe discharge outlet member having an end wall, and a skirt which extends from the end wall and telescopically engages the housing, wherein a silencer element is disposed in the skirt at a position away from the end wall and the secondary fluid flows through the silencer element to displace the silencer element and the discharge outlet member to the extended position.