An investigation has been launched after a French sub-hunting sonar designed for the next generation of European warships sank during trials in the Atlantic, Reuters quoted the company and defence sources as saying today. The $4-million sonar was built by French defence electronics company Thales and is designed to hunt submarines by pinging the depths when deployed on the back of a tow line. It is due to be installed on state-of-the-art FREMM stealth frigates, under construction for France and Italy. Thales confirmed the loss of the sonar and said efforts were under way to understand what happened. "This happened during a test of a towed variable-depth sonar. It was lost during trials and the incident is under investigation," a spokesman for the French company said. Defence sources said the device had been lost in deep waters during rough weather in the Bay of Biscay, where it was being tested from the deck of a German-owned vessel two weeks ago. The loss of such equipment, whose exact performance criteria are classified, could be viewed as a security risk. But it lies in waters several kilometres deep, meaning neither France nor its rivals would find it easy to retrieve it from the seabed. "If it is in the Bay of Biscay, then it will be quite tough to recover," a European naval source told Reuters. France's DGA defence procurement agency, which ordered the CAPTAS 4249 sonar, had no immediate comment. The lost device is an active and passive sonar, meaning it can both transmit signals at low frequency to detect submarines or listen passively for threats such as a torpedo attack. It can be raised to within a meter of the surface or plunge as low as 250 metres (yards) to find the best performance, which depends on the layers of temperature and salinity of the water. Sonars are vital to the cat-and-mouse game of submarine detection still played out daily between Western and Russian fleets in the Atlantic, two decades after the Cold War ended. Defence contractors have been racing to modernise sonars to cope with quieter submarines and to dampen unwanted noise from other objects or from reverberation in shallow waters. Thales recently upgraded the sonars on anti-submarine patrols used by Type 23 frigates in Britain's Royal Navy.
