Abstract: The specification describes a butterfly flap valve comprising a flap which on opening is adapted firstly to be axially displaced and then turned. For operating the flap a shaft extends transversely to the direction of flow into the housing of the valve and carries fixed on it an arm lever which is pivotally connected with the flap. In a plane spaced from the plane of the lever the flap is connected with a link which is pivotally connected with the housing. The link and the lever form an articulated quadrilateral which is staggered so as to lie in two planes.