Naval ships, designed to avoid detection by enemy fleets and aircraft, are exempt from an international requirement that vessels automatically and continuously broadcast their position, course and speed. They tend to have fewer lights than many commercial vessels, making them harder to pick out. They are painted gray to blend into the sea during wartime but become even more difficult to spot at night. And a growing number of modern naval vessels, including the John S. McCain, are designed to scatter incoming radar signals, so that they are less detectable.More information at the New York Times.
The Maritime and Port Authority of Singapore told The Straits Times, a Singapore newspaper, that the government’s vessel traffic information system did not know the John S. McCain was there until the tanker, the Alnic MC, carrying 12,000 metric tons of fuel oil, delivered a crushing blow to the warship’s left side. Two sailors from the ship, a guided-missile destroyer, are dead, and eight more are listed as missing, as divers have begun discovering human remains inside the vessel’s mangled decks.The Singaporean agency told The Straits Times that it had not detected the destroyer on radar and that its traffic information system had not picked up data on the ship. In addition to radar, traffic information systems rely on data from the so-called Automatic Identification Systems that all but the smallest commercial vessels are required to use to broadcast information about their whereabouts.
Military vessels typically carry the systems but often turn them off because the captains do not want to reveal so much information.