The changing balance between the Yorktown class, the Essex class and armoured-flight-deck carriers, 1937–45

Abstract

World War II aircraft-carrier design required navies to balance aircraft capacity, armour, speed, stability, endurance and anti-aircraft defence within a limited displacement. The Yorktown class, introduced in 1937, established the main American approach: a large air group supported by speed and active defence. The Essex class, introduced at the end of 1942, enlarged this concept and normally operated between 90 and 100 aircraft. British carriers accepted smaller air groups in exchange for armoured flight decks and protected hangars.

The comparison was not simply wooden decks against armoured decks. American carriers possessed armour below the flight deck, while their larger air groups provided fighters capable of intercepting attacks at distance. Kamikaze operations from October 1944 demonstrated that active defence could be penetrated. The most effective arrangement therefore combined aircraft, radar, anti-aircraft guns, structural protection, escorts and damage control.

Overview

Carrier designers could not maximise every desirable quality. Armour added weight, particularly damaging topweight when placed at flight-deck level. Aircraft required not only deck space but hangars, fuel, ammunition, workshops, elevators and maintenance personnel. Increasing one capability usually restricted another unless the navy accepted a larger and more expensive ship.

The United States emphasised aircraft capacity and offensive reach. Britain placed greater emphasis on surviving air attack in restricted waters such as the Mediterranean. Both approaches were rational responses to different operational expectations.

Glossary

Aircraft capacity: The number of aircraft embarked, although actual complements varied by mission and aircraft type.

Armoured flight deck: A flight deck incorporating armour as part of the ship’s protection.

Combat air patrol: Fighters maintained over a fleet to intercept approaching aircraft.

Deck park: Aircraft stored on the exposed flight deck rather than inside the hangar.

Displacement: The weight of water displaced by the ship, used as the principal measure of ship size.

Mission kill: Damage that prevents a carrier from conducting flight operations even though it remains afloat.

Ten Key Points

1. Carrier design was a compromise between weight, volume and stability

Armour did not reduce aircraft capacity through weight alone. Aircraft also required hangar volume, fuel tanks, magazines, workshops, spare parts and handling spaces. Armour fitted high in the ship raised the centre of gravity and could reduce stability. Designers then had to widen the hull, reduce other upper weight or accept fewer aircraft. The problem could be reduced by building a larger ship, but larger carriers required more machinery, money, dockyard capacity and crew.

2. Yorktown established the American model in 1937

USS Yorktown was commissioned on 30 September 1937. She displaced approximately 19,800 tons standard and carried about 81–85 aircraft. The Yorktown class therefore did not represent a 60-aircraft design. It already combined a substantial air group with high speed and adequate protection for treaty-limited displacement. The class provided the immediate design foundation for the larger Essex carriers constructed during the war. (Naval History and Heritage Command)

3. Essex entered service on 31 December 1942

USS Essex, the lead ship of the class, was laid down on 28 April 1941, launched on 31 July 1942 and commissioned on 31 December 1942. At approximately 27,100 tons standard displacement, Essex was considerably larger than Yorktown. By the Battle of the Philippine Sea in June 1944, Essex-class carriers normally embarked between 90 and 100 aircraft, including roughly 40 fighters, 35 dive-bombers and 18 torpedo aircraft. (Naval History and Heritage Command)

4. The Essex flight deck was wooden, but the ship was not unarmoured

The Essex class used a steel flight-deck structure covered with wooden planking rather than an armoured flight deck. Its principal strength and protective deck was located at hangar-deck level. The official damage report for USS Franklin described this deck as two layers of 1¼-inch Special Treatment Steel. This arrangement protected machinery and spaces below but allowed bombs or kamikazes to penetrate the flight deck and enter the hangar. (Naval History and Heritage Command)

5. The American design placed greater weight on aircraft capacity

The larger Essex air group increased offensive striking power, reconnaissance coverage and fleet defence. More fighters could maintain combat air patrols, escort strikes and attack enemy aircraft on their airfields. The open hangar and unarmoured flight deck also provided greater aviation volume and allowed blast and smoke to escape. The cost was increased vulnerability in the flight-deck, gallery-deck and hangar spaces when an attacker penetrated the outer defensive screen.

6. British carriers accepted smaller air groups for stronger deck protection

British armoured carriers were designed partly for operations near hostile land-based aircraft in the North Sea and Mediterranean. By 1945, British fleet carriers operating near Okinawa generally embarked about 45–50 aircraft, considerably fewer than the 90–100 carried by an Essex. Their armoured flight decks, however, prevented several kamikazes from penetrating into the hangar. On 9 May 1945, two kamikazes reportedly ricocheted from HMS Victorious. (Naval History and Heritage Command)

7. Aircraft provided the best first line of defence

Destroying an attacker before it reached the carrier was more effective than absorbing its impact. Radar-directed fighters could intercept enemy aircraft tens of miles from the task force. At the Battle of the Philippine Sea on 19–20 June 1944, American radar, fighter direction and large numbers of F6F Hellcats inflicted severe losses on Japanese naval aviation. Extra fighters therefore provided both offensive strength and active protection. Aircraft numbers alone, however, did not guarantee successful interception. (Naval History and Heritage Command)

8. Kamikaze attacks changed the defensive problem in October 1944

Japan began organised kamikaze attacks during the Philippines campaign in October 1944. A conventional pilot usually attempted to release a weapon and escape. A kamikaze pilot deliberately continued towards the ship after suffering damage. Fighters or anti-aircraft guns could disable the aircraft without preventing its wreckage, engine, bomb and burning fuel from striking the carrier. This reduced the reliability of active defence and increased the value of structural protection and damage control. (Naval History and Heritage Command)

9. Intrepid demonstrated the Essex trade-off in 1944–45

USS Intrepid, commissioned on 16 August 1943, was hit by kamikazes on 25 November 1944 and again on 16 April 1945. During the April attack, two aircraft penetrated the fighter and gun screen. One crashed through the flight deck near the after elevator and drove engine and fuselage sections into the hangar. The crew controlled the fires, but the damage forced the carrier to withdraw for repairs. (Naval History and Heritage Command)

10. Neither aircraft nor armour provided a complete answer

The American system reduced the likelihood of attack through offensive strikes, radar warning, combat air patrols and heavy anti-aircraft fire. British armour reduced the consequences when attackers reached the ship. USS Franklin survived catastrophic damage on 19 March 1945 because the armoured hangar deck protected the principal hull structure and machinery, but her aviation spaces were devastated. The later 45,000-ton Midway combined an armoured flight deck with more than 100 aircraft, showing that greater displacement could reduce the original compromise. (Naval History and Heritage Command)

Conclusion

The Essex class represented the most effective design for the United States Navy’s Pacific strategy. Introduced on 31 December 1942, it combined speed, endurance, heavy anti-aircraft armament and an air group of approximately 90–100 aircraft. These aircraft allowed American task forces to attack enemy airfields, maintain combat air patrols and conduct large offensive strikes.

The Essex class did not increase capacity from 60 aircraft in Yorktown to 90. Yorktown already carried approximately 81–85 aircraft. Essex enlarged and improved an established American design philosophy.

Aircraft were the most effective first line of defence because they could prevent an attacker from reaching the carrier. Kamikaze operations nevertheless demonstrated that no fighter or gun screen could provide complete protection. Once an attacker reached the ship, an armoured flight deck reduced penetration and protected the hangar more effectively.

The strongest carrier defence was therefore layered:

• radar and early warning;

• fighter interception;

• anti-aircraft gunfire;

• escorts and radar pickets;

• armour and structural protection;

• disciplined damage control.

The central trade-off was not aircraft or armour. It was how much of each capability could be incorporated within the ship’s displacement, volume, stability and intended operational role.

Official Sources and Records

• United States Navy, Naval History and Heritage Command, Dictionary of American Naval Fighting Ships: official entries for USS Yorktown, USS Essex, USS Intrepid and USS Franklin, covering commissioning dates, displacement, aircraft complements, operations and battle damage.

• United States Navy, Bureau of Ships (1946), USS Franklin (CV-13), War Damage Report No. 56, Washington, DC; technical analysis of flight-deck penetration, hangar fires, secondary explosions and the protective effect of the armoured hangar deck.

• United States Navy, Commander in Chief, United States Fleet (1945), Antiaircraft Action Summary: Suicide Attacks, COMINCH P-009, Washington, DC; wartime analysis of kamikaze tactics and fleet air defence.

• United States Navy, Naval History and Heritage Command, Operation Forager and the Battle of the Philippine Sea; official analysis of Essex-class air groups, radar warning and fighter interception in June 1944.

• United Kingdom, Roskill, S.W. (1954–61), The War at Sea 1939–1945, Volumes I–III, History of the Second World War, United Kingdom Military Series, London: HMSO.

References

Naval History and Heritage Command (2019) ‘Operation Forager and the Battle of the Philippine Sea’, H-Gram 032. Washington, DC: Department of the Navy.

Naval History and Heritage Command (2020) ‘The Naval Battle of Okinawa’, H-Gram 045. Washington, DC: Department of the Navy.

O’Brien, P.P. (2015) How the War Was Won: Air–Sea Power and Allied Victory in World War II. Cambridge: Cambridge University Press, chapters 10–11.

Olsen, J.A. (ed.) (2010) A History of Air Warfare. Washington, DC: Potomac Books, chapter 3.

Roskill, S.W. (1954–61) The War at Sea 1939–1945. Volumes I–III. London: HMSO.

United States Navy, Bureau of Ships (1946) USS Franklin (CV-13), War Damage Report No. 56. Washington, DC: Department of the Navy.

Winton, J. (1976) Air Power at Sea, 1939–45. London: Sidgwick & Jackson, chapters 11–12.