Essex Class, U.S. Fleet Carriers

National Archives #80-G-68097

Specifications:

The Essexes were completed in 1942-1945. They were the definitive American carrier type of the war, incorporating the lessons of the previous highly successful Yorktown class. They were intended for mass production and 11 were initially ordered. Five of these were laid down before war broke out. Two more were ordered in 1941 and another 13 in 1942 and 1943, of which 17 were commissioned and 15 reached the combat zone by the time the war ended. Seven more were completed postwar, but the remaining two, plus six ordered in 1944, were cancelled in favor of the Midway class. Production was streamlined through the use of highly standardized components, reducing construction time to as little as 14 months.

The design emphasized offensive fighting power rather than passive defense. The ships' own aircraft were considered its most important protection, followed by its ample antiaircraft defenses. The armor protection was designed against 6" shells only and did not include the hangar deck. This permitted a large air group and an open hangar design that allowed aircraft to warm up their engines on the hangar deck. However, the unprotected hangar proved vulnerable to bomb damage and kamikaze attack, particularly when armed and fueled aircraft were present. Though none of these ships were sunk during the war, Franklin and Bunker Hill took horrible damage from fires and secondary explosions after being hit in their hangar decks. Their survival was a tribute both to the design of the ships and the quality of American damage control procedures and training.

The underwater protection was designed to withstand up to 500lbs (230kg) of TNT, which was inadequate to prevent penetration by the large Japanese torpedo warheads but was enough to localize damage. It consisted of two outer compartments of fuel oil and two inner void spaces, with the frames staggered to avoid transmitting the shock of an explosion directly to the holding bulkhead. This consisted of almost 2" (50mm) of Special Treatment Steel (STS) which was highly resistant to splinters. STS was used extensively as a structural material wherever armor protection was also desirable, including the hangar deck, the fourth deck, and many other areas of the ship.

The air group was initially specified as four squadrons of 18 aircraft, as with earlier American carriers, but with room for a reserve squadron and space for 25% replacement parts. However, the reserve squadron became part of the standard air group almost as soon as the ships entered service, and by the end of the war as many as 102 aircraft were operated (6 fighters, 66 fighter-bombers, 15 dive bombers, and 15 torpedo bombers.)

Their machinery was very robust, as shown by the experience of Franklin, which had her boilers flooded with cold seawater but immediately restored power without serious damage to her propulsion plant. The machinery was divided among four boiler rooms and two engine rooms, the aft engine room driving the inner shafts and the forward engine room driving the outer shafts. Each boiler room had two Babcock and Wilson boilers operating at 565 psi (3820 kPa) at 850 degrees Fahrenheit (450 degrees Centigrade) employing both preheat and superheat features. The Westinghouse turbines consisted of paired low-pressure and high-pressure turbines driving a double-reduction gearbox. An astern turbine was fitted to the rear of each low pressure turbine and a cruising turbine to the front of each high pressure turbine. The cruising turbine was used for efficiency at low power and was bypassed (the steam being fed directly to the high-pressure turbine) when higher power was needed.

Electrical power was supplied by four 1250 kW turbo-generators tied to the main boilers. Emergency power was suplied by two 250 kW diesel generators in the machine spaces and three 60 kW generators on the hangar deck. Nine separate fire pumps were provided, which were also used for washing the deck and could be used for pumping out flooded compartments.

The antiaircraft battery of twelve 5”/38 antiaircraft guns, supplied with VT (proximity fuse) shells, was a terror to attacking aircraft. It was supplemented by light antiaircraft which, by the time the war ended, consisted of up to 72 40mm guns and 60 20mm guns. Eight of the 5" guns were mounted in twin turrets fore and aft of the island, where they had excellent fire arcs. However, their blast was capable of damaging aircraft on the flight deck, a problem that was corrected in the Midway class by having all its heavy antiaircraft guns mounted on sponsons at the level of the hangar deck.

The first ten ships of the class had bows flush with the forward flight deck. These proved vulnerable to storm damage and the last fourteen ships were completed with their hulls extended 12 feet (4 meters) further forward. This also provided space for four more 40mm guns to provide antiaircraft protection from dead ahead.

If the ships had any particular weakness, other than the wooden flight decks, it was that they lacked stability due to the unexpected weight of the antiaircraft guns, radars, and modern naval aircraft added during the war. Designers feared that three torpedo hits would be enough to capsize one of the ships. However, their stability was never seriously tested in battle.

Units in the Pacific:

References

Chesneau (1992)

DANFS

Friedman (1983)

Roberts (1982)

Worth (2001)

The Pacific War Online Encyclopedia (c) 2007-2008 by Kent G. Budge. Index

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