Castle-class corvette design and anti-submarine fit

The Castle class is described as a further development of the original and modified Flower designs. The quoted displacements are 940 tons for the original Flower, 1,030 for the modified Flower, and 1,077 for the Castle. Official Castle performance is given as 16.5 knots and 9,500 nautical miles at 10 knots. Type 144Q and Type 147B sonar accompany Type 272 radar. Squid and a rail carrying fifteen depth charges provide the principal anti-submarine weapons, while a single 4-inch dual-purpose gun and 20 mm weapons cover other threats. The high- and low-angle 4-inch mounting allows attacks on surfaced submarines, other ships, and aircraft. Claims that the class was too slow to catch surfaced Type VII boats receive a qualification: its record of successful attacks makes that criticism seem overstated.