Common Heritage, Launch and Recovery System and Logistics with A18-M

ECA Group launched a towed version of its established A18-M autonomous underwater vehicle (AUV), which was launched in 2016. Capable of being operated by an unmanned surface vessel (USV), the T18-M towed sonar shares the same launch and recovery system (LARS) and logistics support, including training and maintenance, with the A18-M. With the increasing number of drones, the pooling of LARS and logistic support has become a critical measure of efficiency and space savings for both motherships and USVs carrying drones.

The T18-M is an A18-M with its nose replaced replaced by one equipped with rudders and a towing point, and removal of the rear-mounted thruster. Consequent free space makes it possible to integrate a longer interferometric synthetic aperture sonar (SAS) antenna to achieve detection performance at highest speeds.

Like a conventional towed sonar, the T18-M meets all mine warfare recommendations, especially the detection or classification phases. Like the A18-M, it meets STANAG 1364 to minimise acoustic and magnetic signatures and to be able to fly near mines without triggering them. It is equipped with the A18-M’s inertial navigation system which ensures very precise positioning in the minefield.

Conventional towed sonars receive their energy from the towline, whereas the T18-M is self-powered. Without electrical conductors, the towing cable can be smaller and lighter, which has several advantages:

First, the performance of towed sonar at depth is very much related to cable drag, and therefore to its diameter. As a result, the T18-M has outstanding navigational performance, even a long cable has been deployed and even at high sea speeds, thanks to the reduced diameter of the cable;

Second, a smaller cable can reduce the size and power of the winch on the carrier boat and the towing power requirement, and therefore the size of the boat’s engines, which is particularly important when towed sonar is launched from a USV, in which circumstance the drone reduces crew exposure to the minefield. In order to avoid motherships having to be too large, the USVs should be as compact as possible – the smaller they are, the smaller will be the boats which embark them;

Third, energy on board the towed vehicle avoids having an electric generator on the towing boat, which saves space and weight (very useful for a small USV) and also provides greater operational reliability and electrical safety for the crew operating the towing boat;

Since the A18-M and T18-M are very similar, ECA designed a common LARS for automatic launching and recovery of both of them from a USV. This point significantly reduces the reconfiguration time of the USV between an AUV mission and a towed sonar mission, which is a great operational advantage.