Azimuth Stern Drive Tug

Harbour or escort tug equipped with two stern-mounted azimuth (Z-drive) thrusters, each capable of independent 360° rotation. The arrangement gives full omnidirectional thrust without rudders, allowing the tug to apply force at any heading without losing manoeuvrability. ASDs typically carry bollard pulls of 60–90 t and reach speeds of 12–14 knots, making them the dominant harbour-tug type in modern container and tanker terminals. Compared with conventional twin-screw tugs they offer faster reaction in escort work and are easier to operate at low speed without girting risk.