Escort Towage

Escort towage is the active steering, braking and control of a ship that has lost propulsion or steering, by a tug connected to its stern while the ship is making way. Bureau Veritas defines it in terms of indirect towing mode with the escorted ship’s ahead speed in a typical range of 6 to 10 knots, and caps design maximum escort speed at 10 knots, accepting 12 knots case by case for tugs whose free running speed exceeds 15 knots.

In indirect mode the towline and the propulsors hold the tug at a large drift angle and the hull and skeg generate lift and drag, so the hull carries the load rather than the propellers. A sponsoned escort hull of about 80 tonnes bollard pull produces braking force of roughly 120 to 130 tonnes and steering force of roughly 70 to 90 tonnes at 10 knots. The gain is a property of the hull form and does not transfer between designs.

The full article will cover direct and indirect mode, transverse arrest, the class notations that state the certified force matrix, ASTM F1878-21 and ISO 4827:2022, and the national escort mandates in United States and Washington State waters.