H-4 Catapult

History

The H Mk IV was the hydraulic catapult used on the Essex class aircraft carriers. Development began in 1939 with the requirements to launch aircraft up to 16000 pounds at 90 mph in an 95 feet run. An early requirement to launch seaplanes as well lead to the related H-5 Catapult. In 1940, a requirement for a hangar deck catapult with a 73.5 feet run was added which became the H 4A, the flight deck type being renamed H 4B. Another modified version for CVE use was designated H 4C, differing from H 4A in that it had one rather than two shuttles. H 4-1 was a modified, lengthened type for use in the Midway class aircraft carriers.

The first airplane launch of an H 4 catapult was in 1943. The first installation on a ship was the Lexington in 1943, but it was first tested at sea on Yorktown.

Characteristics:

• H 4A: 16000 pounds at 85 mph in 72 feet 6 inches, recharge in 60 seconds.
• H 4B: 18000 pounds at 90 mph in 96 feet 8 inches, recharge in 42.8 seconds.
• H 4-1: 28000 pounds at 90 mph in 150 feet, recharge in 60 seconds.

Hangar deck catapults were oredered removed from Essex class carriers in May 1943, converting them to regular H 4s.

Used on

H 4A & H 4B

• Essex class

H 4C

• Escort carriers?

H 4-1

• Midway class

Part description

The part shows the top view of the component. As these were recessed in the deck, they are not visible in the sideview. The part shows the H 4-1.