Abstract: A vectorable exhaust nozzle 17 for a gas turbine engine comprises a fixed duct 21 and a cowl 22 pivotably attached to the duct 21 to facilitate rotation of the cowl 22 about a horizontal axis transverse to the exhaust stream issuing from the duct 21. The nozzle 17 further comprises a flap 23 pivotably attached to the lower downstream edge of the duct 21 for rotation about a second horizontal axis transverse to the exhaust stream and an actuation means 28 for rotating the cowl 22 and flap 23. The cowl 22 and flap 23 communicate via at least one link member 24. The actuation means 28 rotates the cowl 22 which, by way of the link members 24, rotates the flap 23 in the same direction. The nozzle 17 defined by the sidewalls 22a and the interconnecting curved wall 22b of the cowl 22 and the downstream edge of the flap 23, is thus vectored from a direction facing rearwards to a direction facing downwards.

Abstract: A dual cycle vectored thrust engine has a flow control valve for changing the cycle from a pure jet for supersonic operation to by-pass cycle for vertical take-off. The valve has two separate inlets, two separate outlets and passageways within the valve which provide flow communication between the inlets and the outlets, one part of the valve being rotatable relative to the other to change the direction of flow through one of the inlets from communication with one of the outlets to communication with the other of the outlets. The passageways leading to one of the outlets are shaped to turn the flow through up to 180.degree. to enable the flow to be passed to front vectorable nozzles upstream of the valve.