Abstract: A variable vane assembly, for example of stator vanes in a gas turbine engine, comprises vanes which can be turned together about their longitudinal axes by means of a unison ring which is turned by an actuator about the engine axis. The unison ring is coupled to the vanes by levers. The unison ring has varying stiffness along its circumference, increasing in the direction away from the drive point at which the actuator acts. The varying stiffness may be achieved by varying the radial thickness of the unison ring. The unison ring is thus able to resist ovalization so that the vanes move together.

Abstract: A variable vane assembly, for example of stator vanes in a gas turbine engine, comprises vanes 16 which can be turned together about their longitudinal axes by means of a unison ring 26 which is turned by an actuator 28 about the engine axis. The unison ring 26 is coupled to the vanes 16 by levers 24. The unison ring 26 has varying stiffness along its circumference, increasing in the direction away from the drive point 58 at which the actuator 28 acts. The varying stiffness may be achieved by varying the radial thickness of the unison ring 26. The unison ring is thus able to resist ovalisation so that the vanes 16 move together.