Tractor Tug

A tug with its propulsion units forward of midships, giving high control and strong indirect (lift) towing when working on a line aft. Two forms exist: the Voith-Schneider tractor, using cycloidal vertical-blade propellers, and the forward azimuth (Z-drive) tractor; both let the tug develop steering force from water flow across its skeg while held by the towline. This contrasts with the ASD tug, whose azimuth drives sit aft. Tractor tugs are favored for ship escort and berthing where fast, fine thrust-vectoring and high indirect bollard pull matter.