Black Swan-class sloop

The Black Swan class and the Modified Black Swan class were two classes of sloop built for the Royal Navy and the Royal Indian Navy as specialised convoy-defence vessels. Twelve Black Swans were launched between 1939 and 1943 and twenty-five Modified Black Swans between 1942 and 1945. The first two ships were built under the 1937 Programme and ordered from Yarrow and Company at Scotstoun on 1 January 1938, and Yarrow later received orders for further sloops, among them two for the Royal Indian Navy. Unlike corvettes, which were based on a merchant design with triple expansion engines, the sloops were conventional naval vessels with turbines, larger and faster than a corvette and armed with high angle 4 inch guns with good anti-aircraft fire control while keeping a strong anti-submarine capability. They had a longer range than a destroyer at the cost of a lower top speed. In World War II the class sank 29 U-boats, and Captain Frederic John Walker in the sloop Starling became the most famous sloop commander.