USS St. Simon (CVE-51) (originally AVG-51 then later ACV-51), an escort aircraft carrier originally classified as an auxiliary aircraft carrier, was laid down on 26 April 1943 at Tacoma, Washington, by the Seattle-Tacoma Shipbuilding Corporation, under a Maritime Commission contract (MC hull 262); reclassified as an escort aircraft carrier, CVE-51, on 15 July 1943; launched on 9 September 1943; sponsored by Mrs. R. H. Lewis, the wife of Major General R. H. Lewis, Commanding General, Northwestern Sector, Fort Lewis, Washington; assigned to the Commercial Iron Works, Portland, Oregon, for the completion of construction; and delivered to the Royal Navy, under lend-lease, on 31 December 1943.
Renamed HMS Arbiter (D31) (while being carried on the United States' Naval Vessel Register with the classification BCVE-51), the escort carrier served in the Royal Navy for the duration of World War II. She earned "battle honors" in the Atlantic during 1944, serving on the western approaches to the British Isles, and in 1945 served as one of seven similar ships engaged in operating as an aircraft ferry supporting the British Pacific Fleet's train, bringing up replacement aircraft or providing combat air patrol for replenishment ships.
Returned to Norfolk, Virginia, on 23 February 1946, she was accepted by the United States Navy on 3 March 1946. Struck from the Navy list on 12 April 1946, the ship was sold to the Newport News Shipbuilding and Dry Dock Company, Newport News, Virginia, on 30 January 1947. Converted to the cargo ship Coracero, the former escort carrier served under two more names, President Macapagal from 1965 to 1972 and Lucky Two in 1972 before she was scrapped in Kaohsiung, Taiwan, in 1972.
Design and description
These ships were larger and had a greater aircraft capacity than all the preceding American-built escort carriers. They were also all laid down as escort carriers and not converted merchant ships. The ship displaced standard and full load. Propulsion was provided by a General Electric geared steam turbinefed with steam by two Foster Wheeler boilers, and driving one shaft. The machinery was rated at , giving a speed of .
Aircraft facilities were a small combined bridge/flight control on the starboard side, two aircraft elevators by in size, one aircraft catapult and nine arrestor wires. She was launched on 9 September 1943, sponsored by Mrs. R. H. Lewis, the wife of Major General R. H. Lewis, Commanding General, Northwestern Sector, Fort Lewis, Washington and was completed at the Commercial Ironworks of Portland, Oregon.
Following commissioning, Arbiter underwent modification for Royal Navy service at Esquimalt in Western Canada,