The ILLUSTRIOUS CLASS was a class of aircraft carrier of the Royal
Navy that included some of the most important British warships in
World War II. They were laid down in the late 1930s as part of the
rearmament of British forces in response to the emerging threats of
The Illustrious class comprised four vessels: HM Ships Illustrious ,
Formidable , Victorious and Indomitable . The last of these was built
to a modified design with a second, half-length, hangar deck below the
main hangar deck. Each of these ships played a prominent part in the
battles of World War II. Victorious took part in the pursuit of the
German battleship Bismarck
The later two ships of the Implacable class were also built to modified designs in order that they could carry larger air wings . Implacable and Indefatigable both had two hangar levels, albeit with a limited 14-foot (4.3 m) head room.
* 1 Design and concept
* 2 Ships in class
* 2.1 Fate of the class
* 3 Notes * 4 See also * 5 References * 6 External links
DESIGN AND CONCEPT
The Illustrious class was designed within the restrictions of the Second London Naval Treaty , which limited carrier size to an upper limit of 23,000 tons. They were different in conception to the Royal Navy's only modern carrier at the time, their predecessor HMS Ark Royal , and what may be described as their nearest American contemporaries, the Yorktown and Essex class carriers. The Illustrious class followed the Yorktown but preceded the Essex.
Where other designs emphasised large air groups as the primary means of defence, the Illustrious class relied on their anti-aircraft armament and the passive defence provided by an armoured flight deck for survival; resulting in a reduced aircraft complement. Other carriers had armour carried on lower decks (e.g. the hangar deck or main deck); the unprotected flight deck and the hangar below it formed part of the superstructure , and were unprotected against even small bombs. However, the hangar could be made larger and thus more aircraft could be carried, but the differences in aircraft capacity between these carriers and their United States Navy (USN) counterparts is largely due to the USN's operational doctrine, which allowed for a permanent deck park of aircraft to augment their hangar capacity. Illustrious's hangar was 82% as large as USS Enterprise 's but Enterprise typically carried 30% of her aircraft capacity in her deck park. Indomitable's two hangars were actually larger than Enterprise's but she carried fewer aircraft because she did not have a large permanent deck park. In 1944/45 RN carriers began to carry a permanent deck park of similar size to their USN counterparts and this increased their aircraft complement from 36 to an eventual 57 aircraft in the single hangar carriers, and from 48 up to 81 in the double hangar, 23,400 ton Implacable design, compared to 90–110 for the 27,500 ton US Essex class.
In the Illustrious class, armour was carried at the flight deck level—which became the strength deck—and formed an armoured box-like hangar that was an integral part of the ship's structure. However, to make this possible without increasing the displacement it was necessary to reduce the overhead height of the hangars to 16 ft (4.88 m) in the Illustrious class hangars and 14 ft (4.27 m) in the upper hangar of the Indomitable and 16 ft (4.88 m) in her lower hangar; these compared unfavourably to the 17 feet 3 inches (5.3 m) of the Essex class, 17 ft 6 inches (5.38 m) in Enterprise and 20 ft (6.10 m) in Saratoga. This restricted operations with larger aircraft designs, particularly post-war.
This armour scheme was designed to withstand 1,000 pound bombs (and heavier bombs which struck at an angle); in the Home and Mediterranean theatres it was likely that the carriers would operate within the range of shore-based aircraft, which could carry heavier bombs than their carrier-based equivalents. The flight deck had an armoured thickness of 3 inches, closed by 4.5-inch sides and bulkheads. There were 3-inch strakes on either side extending from the box sides to the top edge of the main side belt, which was of 4.5 inches. The main belt protected the machinery, petrol storage, magazines and aerial weapon stores. The lifts were placed outside the hangar, at either end, with access through sliding armoured doors in the end bulkheads.
Later in the war it was found that bombs which penetrated and detonated inside the armoured hangar could cause structural deformation, as the latter was an integral part of the ship's structure.
Pre-war doctrine held that the ship's own firepower, rather than its
aircraft, were to be relied upon for protection, since in the absence
of radar, fighters were unlikely to intercept incoming attackers
before they could release their weapons. Accordingly, the Illustrious
class was given an extremely heavy Anti-Aircraft armament. The
armament was similar to Ark Royal with twin 4.5 inch turrets (in a new
"between-decks" or countersunk design) arranged on the points of a
quadrant. The guns were mounted sufficiently high so that they could
fire across the decks; de-fuelled aircraft would be stowed in the
hangar for protection during aerial attack. The Illustrious Class were
fitted with four
HACS controlled High Angle Director Towers, for fire
control of her 4.5" guns. Illustrious pioneered the use of
SHIPS IN CLASS
NAME PENNANT BUILDER ORDERED LAID DOWN LAUNCHED COMMISSIONED FATE
Formidable 67 Harland "> Victorious in 1959
All four early ships were hard worked during World War II, with
Illustrious and Formidable suffering and surviving heavy damage. Like
their contemporary USS Enterprise they fought a long and consuming war
and despite significant overhauls and repair of battle damage, were
worn out by 1946 and were scrapped in the mid-1950s. Due to a variety
of factors including Britain\'s dire post war finances , and the
consequent reductions in the size of the
* ^ Friedman, pp.18-19.
* ^ Hone, Friedman, Mandeles, British and American Carrier
Development, 1919–1941, p125: "The 1931 edition of "Progress in
Tactics" included a section on foreign tactics, including operating
practices. The U.S. portion mentioned that "the number of aircraft in
carriers is proportionately much higher than in our Navy, largely due
to the practice of storing some aircraft permanently on deck."
* ^ Friedman, in his works on RN (p.154) and USN (P.392), aircraft
carriers states that Enterprise's hangar measured 546 feet x 63 feet
versus 456 x 62 feet for the Illustrious class, therefore Illustrious'
hangar had 82% of Enterprise's hangar capacity.
* ^ Friedman 1988, p. 145
* ^ USS Bennington, Action Report, OPERATIONS IN SUPPORT OF THE
OCCUPATION OF OKINAWA INCLUDING STRIKE AGAINST KANOYA AIRFIELD,
KYUSHU. 28 May to 10 June 1945, p.18. On June 05 1945, USS Bennington
reported that her maximum hangar capacity was 51 aircraft, 15 SB2Cs
and 36 F4Us, and that 52 were carried as a deck park. At that time she
carried 15 TBMs, 15 SB2Cs and the rest were a mix of F6Fs and F4Us.
She was prompted to utilize, and report on, her maximum hangar storage
due to a Typhoon.
* ^ Friedman
* ^ Thomas, Andrew,
* Brown, David (1977). WWII Fact Files: Aircraft Carriers. New York: Arco Publishing. ISBN 0-668-04164-1 . * Campbell, John (1985). Naval Weapons of World War II. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-459-4 . * Chesneau, Roger (1995). Aircraft Carriers of the World, 1914 to the Present: An Illustrated Encyclopedia (New, Revised ed.). Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-902-2 . * Chesneau, Roger, ed. (1980). Conway's All the World's Fighting Ships 1922–1946. Greenwich, UK: Conway Maritime Press. ISBN 0-85177-146-7 . * Friedman, Norman (1988). British Carrier Aviation: The Evolution of the Ships and Their Aircraft. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-054-8 . * Friedman, Norman (1983). U.S. Aircraft Carriers: An Illustrated Design History. Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-739-9 . * Hobbs, David (2013). British Aircraft Carriers: Design, Development and Service Histories. Barnsley, UK: Seaforth Publishing. ISBN 978-1-84832-138-0 . * McCart, Neil (2000). The Illustrious & Implacable Classes of Aircraft Carrier 1940–1969. Cheltenham, UK: Fan Publications. ISBN 1-901225-04-6 . * Rohwer, Jürgen (2005). Chronology of the War at Sea 1939-1945: The Naval History of World War Two (Third Rev ed.). Annapolis, Maryland: Naval Institute Press. ISBN 1-59114-119-2 .