The USN studied the superior defensive qualities of Royal Navy armoured carriers and this analysis is partly revealed in the damage report following the attack on Franklin on 13 March 1945: As a result of study of damage sustained by various British carriers prior to our entry into the war, two important departures from traditional U.S. Navy carrier design were incorporated in the CVB Class, then still under development. HMS ILLUSTRIOUS in an action off Malta on 1 January 1941 was hit by several bombs, three of which detonated in the hangar space. Large fires swept fore and aft among parked planes thereby demonstrating the desirability of attempting to confine the limits of such explosions and fires by structural sectionalization of the hangar space. On the CVB Class the hangar was therefore divided into five compartments separated by 40 and 50-pound STS division bulkheads extending from the hangar deck to the flight deck, each fitted with a large door suitable for handling aircraft. It is hoped that this sectionalization, in conjunction with sprinkler and fog foam systems, will effectively prevent fires from spreading throughout the hangar spaces, as occurred on FRANKLIN on 30 October and 19 March. The damage experiences of several British carriers, which unlike our own were fitted with armoured flight decks, demonstrated the effectiveness of such armour in shielding hangar spaces from GP bombs and vital spaces below the hangar deck from SAP bombs. Accordingly, the CVB Class was designed with an armoured flight deck consisting of 3-1/2-inch STS from frames 46 to 175 with a hangar deck consisting of two courses of 40-pound STS between frames 36 and 192. Although none of the CVB Class carriers were completed in time to take part in war operations, the effectiveness of armoured flight decks against Kamikaze attacks was demonstrated by various carriers attached to the British Pacific Fleet. Reference (k) reports two such interesting cases. The VICTORIOUS was struck by three Kamikaze aircraft, two of which ricocheted off the armoured flight deck and over the side, causing no important damage. The third carried a bomb which detonated at frame 30 starboard at the butt of the 3-inch flight deck armour with 1-1/2-inch "D" quality (equivalent to HTS) steel. It does not appear that the Kamikaze actually struck the ship. The bomb detonation, however, depressed the 3-inch deck slightly but did not tear it open. On the other hand, the 1-1/2-inch "D" quality deck plating was ripped open over a total area of about 25 square feet. Two days were required for temporary repairs, at the conclusion of which the ship was fully operational. HMS FORMIDABLE was hit by two bombs, the first of which struck and detonated on the flight deck 9 feet to port of the center-line at frame 79, directly over a deep bent and at a juncture of three armoured plates. The armoured deck was depressed over an area 24 feet long and 20 feet wide. Maximum depression was 15 inches. Adjacent bents spaced 12 feet forward and aft of the point of impact were slightly depressed. A hole 2 square feet in area was blown in the 3-inch deck. Three fragments penetrated downward through the ship into the center boiler room. The damage in this boiler room, which was not described, temporarily reduced speed to 18 knots. The second bomb struck and detonated on the centreline of the flight deck at frame 94. The 3-inch deck and deep bent directly below the point of impact were depressed about 4-1/2 inches and one rivet was knocked out. However, the ship was fully operational within about 5 hours, including flight operations.