The Pacific War Online Encyclopedia

Pennsylvania Class, U.S. Battleships

Naval History and Heritage Command #67583

Schematic diagram of Pennsylvania class battleship

ONI 222

Tonnage	34,823 tons standard displacement
Dimensions	608' by 106'2' by 28'8" 185.32m by 32.35m by 8.8m
Maximum speed	21 knots
Complement	1052
Aircraft	2 catapults 3 seaplanes
Armament	4x3 14"/45 guns 12x1 5"/51 guns 8x1 5"/25 AA guns 4x1 3"/50 AA guns 8 0.50 machine guns
Protection	10,883 tons: 13.5" (343mm) belt tapering to 8" (203mm) below the waterline 1.75"+1.25"+1.25"+0.5" = 3.7" (44mm+32mm+32mm+13mm = 93mm) STS armor deck 4.5" STS + 1.75" MS = 5.5" (114mm STS + 44mm MS = 158mm) over steering spaces 1"/1.5" STS + 0.5" MS = 1.35"/1.85" (25mm/38mm STS + 13mm MS = 34mm/47mm) splinter deck 13" (330mm) bulkheads tapering to 8" (203mm) below waterline 18"/5"STS/9" (457mm/127mm STS/229mm) turret 13" (330mm) barbettes Splinter protection for 5"/25 guns 16" (406mm) conning tower 13" (330mm) uptakes 19' (5.8m) underwater protection consisting of a 0.25" (6mm) retaining bulkhead, an inner 1.5"+1.5" (38mm+38mm) STS torpedo bulkhead, an outer 0.75" (19mm) STS torpedo bulkhead, and blisters. Designed to withstand a 300 lb (136 kg) explosive charge.
Machinery	4-shaft Westinghouse geared turbine (33,375 shp) 6 Bureau Express boilers
Bunkerage	3692 tons fuel oil
Range	6070 nautical miles (11,200 km) at 12 knots
Sensors	CXAM1 air search radar
Modifications	Spring 1942: Replaced 3" guns with 4x4 1.1"/75 AA guns. Added 16x1 20mm Oerlikon AA guns and SR, SK, and SG radar. 1943: 5"/25 guns replaced with 4x2 5"/38 dual-purpose guns with two Mark 37 directors. One catapult removed. Light antiaircraft upgraded to 10x4 40mm Bofors AA guns, 51 20mm guns and 8 0.50 machineguns. 1945: Added 1x2 40mm guns, reduced 20mm battery to 33 guns, and added SP radar.

The Pennsylvanias were completed in 1916. The second of the "standard battleship" classes, they resembled the preceding Nevada class. However, the Pennsylvanias had all triple turrets, for a main battery of twelve 14" (356mm) guns. The protection scheme was almost identical with the Nevadas except for the underwater protection, which benefited from caisson experiments conducted in 1912. The resulting underwater protection system was capable of withstanding a 300 lb (136 kg) explosive charge, which made it the best in the world at the time. The ships also had four propeller shafts instead of two, which improved machinery dispersal and gave enough added power to compensate for the greater displacement.

At the time of their completion, the Pennsylvanias were possibly the finest battleships in the world. By 1941 they were obsolescent, particularly in their antiaircraft defenses, despite modernization in the 1930s that added an antiaircraft battery similar to that of the Nevadas and improved their horizontal and underwater protection and gun elevation.

The more famous ship of this class, Arizona, was wrecked during the attack on Pearl Harbor by an explosion of the forward magazine. Pennsylvania herself was in dry dock and was probably the least damaged of all the battleships present at Pearl Harbor, suffering a single bomb hit that inflicted some casualties but little structural damage.