Worcester class anti-aircraft cruisers of the United States Navy

6-in (152-mm) L/47 DP Mk 16 guns. Note the Mk-27 Fire Control Radars.

Mk34 3in single mount at the fantail with radar antenna mount.

The ships were designed based on the tactical requirement for a large fast warship to protect the fleet in almost any weather, with fuel capacity for long voyages and most important with weapons capable of engaging heavy high-altitude bombers, the first generation of anti-ship missiles introduced by Germany in 1943 and repelling massed air attacks at extended ranges, as well as dealing with multiple surface targets, but also with heavy deck armor to survive high-altitude bombing. Therefore, the two ships were equipped with the first truly dual-purpose gun larger than 5 inch, the first 6-inch gun capable of engaging aircraft in longer distances (23,880 meters maximum range), the recently perfected high-angle automatic 6-in (152-mm) L/47 DP Mk 16, which had fast training and elevation rates and high rate of fire. Also, unlike all previous US 6-inch guns, these could load at any angle, greatly enhancing their use in the anti-aircraft role. Manning was twenty-one crewmembers in the gunhouse, ten in the turret officer’s booth and eleven in the gun house. This was made up of eleven turret controlmen, three gun-laying operators, three gun operators, two hot-case men, and two projectile loaders. The new gun turret was tested first on the gunnery training ship USS Mississippi AG-128 (former BB-41).

A 3in/50 (7.6 cm) Mk 33 twin mount on the USS Wasp (CVA-18)

Cutaway of 6″/47DP (15.2 cm) Mk 16 turret. Via www.navweaps.com

Mk 33 twin mount firing

USS Roanoke as seen from a helicopter

The cruisers, except the 6-inch guns, were equipped with a total of 24 (!) 3-inch (76.2-mm) dual purpose guns on open mounts; five Mk33 twin mounts on the port side, five on the starboard and one in the bow which was later removed. A pair of single Mk34 mounts on blisters were on each side of the fantail. The new 3-inch guns, were designed according to the emerged need for a lighter automatic weapon than the 5-inch guns to stop the Japanese Kamikaze attacks as the 20mm and 40mm guns were proved ineffective for this role. The tests testing showed that against a target representing a Nakajima plane a single rapid-fire 3″/50 (7.62 cm) was as effective as two 40 mm quad mountings and that it could effectively engage at a much longer range (max. range was 13,300 meters and rate of fire 50rds/min). When shooting at aircraft, the gun has to fire at the place in the sky where the aircraft will be when it meets up with the round which has just been fired, based on the radar calculations. The 3in/50 magazine had a capacity of 1,518 rounds. Normal crew for the twin 3in/50 (7.62 cm) was eleven men, including a mount captain, two control station men, four shellmen and four shell passers. However, it was not until 1948 that this weapon was delivered to the fleet in quantity.

Modified photo of a Worcester class anti-aircraft cruiser. For a high resolution image click here.

The Worcester class cruisers, had numerous fire control radars, setting a new standard for a light cruiser. The gun directors were two Mk34 with Mk13 antenna mounts, four Mk37 with Mk 25 radar mounts, four Mk56 with Mk35 antenna mounts, six Mk 27 radar equipment mounted in each of the 6 main turrets and two Mk63 individual radars for the 3in gun single mounts on the stern.

Different views of USS Roanoke cruiser, (1953-54)

Worcester‘s initial radar equipment

Roanoke with mid-life radar equipment

At her commissioning, USS Worcester carried the SR-2 and SG-6 surface search radars on the main mast, the SR-6/SP-6 air search radar on a mast just forward of the rear stack, and the SP-1 height finding direction (air-search) radar on the after mast. The SR-2 proved to be not effective, and was later replaced by the SR-6 from the mast ahead of the after stack, which was in turn removed. The SP-1 radar was replaced later with the newer and more effective SP-8 while the SG-6 was later removed and on the main mast were installed an SP-10 surface search radar and TACAN. The ships received also the AN/SLR-2 ECM system that consisted of various antennas.

Worcester‘s final radar equipment