A vane arm assembly for a gas turbine engine comprising: a vane arm defining an aperture at an end thereof with an aperture wall; a vane stem extending through the aperture of the vane arm; an angled face disposed on an exterior of the vane stem; a wedge face disposed on the aperture wall, the wedge face and the angled face having a corresponding geometry, the wedge face and the angled face in contact with each other in a preloaded condition to transmit torque from the vane arm to the vane stem; an anti-rotation wall disposed on the exterior of the vane stem, the anti-rotation wall angularly offset from the angled face of the vane stem; an anti-rotation surface disposed on the aperture wall and angularly offset from the wedge face of the vane arm, the anti-rotation wall a and the anti-rotation surface having a corresponding geometry, the anti-rotation wall and the anti-rotation surface in contact with each other to maintain torque transmission from the vane arm to the vane stem during a surge condition; and a mechanical fastener retaining a position of the vane arm in the longitudinal direction of the vane stem; characterised in that: the vane arm assembly further comprises an impedance ring disposed within the aperture of the vane arm and within an impedance ring groove defined by the vane stem to provide redundant position retention of the vane arm in the longitudinal direction of the vane stem; and in that the anti-rotation wall is disposed radially outwardly of the angled face, and the impedance ring groove is disposed radially outwardly of the anti-rotation wall, and in that the anti-rotation surface is disposed radially outwardly of the wedge face, and the impedance ring is positioned radially outwardly of the anti-rotation surface. a vane arm defining an aperture at an end thereof with an aperture wall; a vane stem extending through the aperture of the vane arm; an angled face disposed on an exterior of the vane stem; a wedge face disposed on the aperture wall, the wedge face and the angled face having a corresponding geometry, the wedge face and the angled face in contact with each other in a preloaded condition to transmit torque from the vane arm to the vane stem; an anti-rotation wall disposed on the exterior of the vane stem, the anti-rotation wall angularly offset from the angled face of the vane stem; an anti-rotation surface disposed on the aperture wall and angularly offset from the wedge face of the vane arm, the anti-rotation wall a and the anti-rotation surface having a corresponding geometry, the anti-rotation wall and the anti-rotation surface in contact with each other to maintain torque transmission from the vane arm to the vane stem during a surge condition; and a mechanical fastener retaining a position of the vane arm in the longitudinal direction of the vane stem; characterised in that: the vane arm assembly further comprises an impedance ring disposed within the aperture of the vane arm and within an impedance ring groove defined by the vane stem to provide redundant position retention of the vane arm in the longitudinal direction of the vane stem; and in that the anti-rotation wall is disposed radially outwardly of the angled face, and the impedance ring groove is disposed radially outwardly of the anti-rotation wall, and in that the anti-rotation surface is disposed radially outwardly of the wedge face, and the impedance ring is positioned radially outwardly of the anti-rotation surface. the vane arm assembly further comprises an impedance ring disposed within the aperture of the vane arm and within an impedance ring groove defined by the vane stem to provide redundant position retention of the vane arm in the longitudinal direction of the vane stem; and in that the anti-rotation wall is disposed radially outwardly of the angled face, and the impedance ring groove is disposed radially outwardly of the anti-rotation wall, and in that the anti-rotation surface is disposed radially outwardly of the wedge face, and the impedance ring is positioned radially outwardly of the anti-rotation surface.