The Second London Treaty limited the next two aircraft carriers to be only 23,000 tons each.
The Third Sea Lord, Rear-Admiral Henderson, wanted the carriers to have a high level of defense because it was felt they would have to defend against many land based aircraft while in the Mediterranean.
The Illustrious class were the first carriers in the world to have all armored hangars. This was felt that the carrier had to be able to resist fire from 6" guns. The drawback with the armored hangar is it only allowed for one hangar. To save on weight it was decided to go with only one hangar.
The hangar was 458' x 62' x 16'. Thirty torpedo bombers and six fighter/dive bombers could be carried.
There was one 14,000 lb hydraulic catapult located in the flight deck.
The two elevators were 45' x 22'.
Eventually outriggers were installed off the deck to allow up to 54 aircraft to be carried.
Sacrificing hangar armor the HMS Indomitable could carry more planes.
During construction an additional upper hangar was added and it was 458' x 62' x 14'. The forward elevator was 45' x 33' and the aft elevator elevator 45' x 22'.
The lower hanger was 168' x 62' x 16'.
Additional 20 mm guns were added.
The Indomitable had a catapult that could launch 14,000 lbs at 66 knots.
Build under the 1938 Programme.
The Implacable class had a catapult that could launch 16,000 lbs at 66 knots or 20,000 lbs at 56 knots.
The upper hangar was 458' x 62' x 14'. The forward elevator was 45' x 33' and the aft elevator 45' x 22'.
The lower hangar was 208' x 62' x 14' and was located aft.
The short heights on the hangars precluded the Corsair from being carried.
The Implacable class ships were fast enough to keep up with the Essex class ships in the Pacific.