The Big Catapult Airplane

During the 1930s and into the early 1940s, the U.S. Navy considered flying boats the key for long-range scouting for the battle fleet. The aircraft primarily were the Consolidated PBY Catalina and the newly introduced Martin PBM Mariner.¹

The flying boats were supported by a flotilla of seaplane tenders. At the time, it was proposed that a large catapult fitted on a ship could launch the flying boats with greater fuel or weapons loads than was possible with water takeoffs. To demonstrate the feasibility of the concept, the Navy ordered a prototype XPBM-2 aircraft from the Glenn L. Martin Company and ordered a catapult ship—designated AVC-1—from the Philadelphia Navy Yard.

The XPBM-2 was a basic twin-engine, high-wing flying boat of the Mariner series, but with additional fuel tanks and a reinforced airframe to permit catapult launching. It was to have a 4,000-mile range while carrying a significant bomb load. Only one aircraft of that configuration was built.

The AVC-1 resembled a floating dry dock, with a lengthy catapult track through the “well.” She was launched on 17 August 1940, without a ceremony or a sponsor. According to the official Navy record, she was placed in service on 17 December 1941.² Interestingly, although the lighter was commissioned, she was operated under the Commandant of the 4th Naval District with an “in service” status, normally applied to yard and service craft.

The vessel was not self-propelled, had no armament, and, apparently, had no significant accommodations for crew or flight personnel. At one time, however, one officer and about 40 enlisted men were assigned.

There is some indication that during the lighter’s development, the Navy intended to provide diesel propulsion with twin screws; in the event, four diesel generators were installed but no propulsion machinery. Also, although Navy documentation said “no armament authorized,” there were reports that two 20-mm cannon were installed about 1944.³

The hydraulic XH-III aircraft catapult ran most of the AVC-1’s length. It was intended to launch a 60,000-pound PBM at a speed of 120 miles per hour. The lighter’s “stern” was cut away to permit the flying boat to be winched up, onto the catapult, on a dolly. At one point, the Navy considered installing a 75-ton-capacity crane to lift test objects and aircraft onto the catapult; that device also was never provided.

Installation of the AVC-1’s catapult was completed in the summer of 1942, and it was used to launch test objects and the one XPBM-2 built by Martin. Catapult trials were completed by the end of 1942, after which the vessel was employed as a test platform at Philadelphia. Canceled at an early stage were proposals for larger catapult “ships” that could launch 120,000-pound flying boats at a speed of 130 miles per hour. Six such self-propelled catapult ships were envisioned before the concept was dropped. Those ships would have been some 475 feet long.

The status of the AVC-1 was changed to “in service, in reserve” on 16 December 1944, and then to “in commission, in reserve” on 3 March 1945. She then served to test the processes for “mothballing” ships. The vessel was placed “out of service, in reserve” on 8 December 1949.

The AVC-1 was sold in 1956 for scrap, but she survived and was acquired by a commercial firm and employed as a wood-carrying barge. She was employed mainly to carry pine logs from the Bahamas to a paper mill in Jacksonville, Florida, and was referred to as Pulpwood No. 1. It is not clear whether the vessel still exists; however, her post-Navy life was considerably longer than her unique service as a catapult test lighter.

It is difficult to judge whether the AVC-1/XPBM-2 trials were a success because of the early termination of the overall program. The trials were quickly terminated, as the development of jet-assisted take-off (JATO) rocket canisters for short-run water takeoffs alleviated the need for the catapult launching of flying boats.