In the late 1930s, Vought engineer Rex B. Beisel was tasked with designing an observation monoplane aircraft for the U.S. Navy suitable for a multitude of tasks including directing battleship fire. In replacing the standard biplane observation aircraft with a more modern monoplane design, Beisel incorporated innovations becoming the first production type to be assembled with spot-welding, a process Vought and the Naval Aircraft Factory jointly developed to create a smooth fuselage that resisted buckling and generated less drag. Beisel also introduced high-lift devices, spoilers and in a unique arrangement, deflector plate flaps and drooping ailerons located on the trailing edge of the wing were deployed to increase the camber of the wing and thus create additional lift.
For combat missions, the pilot had a .30-caliber machine gun while the radio operator/gunner manned another .30-caliber machine gun (or a pair) on a flexible ring mount. The aircraft could also carry two 100 lb bombs or two 325 lb depth charges. Additionally, the "Kingfisher", as it was designated, served as a trainer in both its seaplane and landplane configurations.
Beisel’s first prototype flew in 1938, powered by an air-cooled, 450 hp Pratt & Whitney R-985-4 Wasp Junior radial engine.
Downed American airmen near Truk await rescue on the wings of an OS2U Kingfisher
The first 54 Kingfishers were delivered to the U.S. Navy beginning in August 1940 and six had been assigned to the Pearl Harbor based Battle Force before the end of the same year. Many of the following 158 OS2U-2s were attached to flight training at Naval Air Station Pensacola, Florida, but 53 were assigned to equip the newly established Inshore Patrol Squadrons, based at NAS Jacksonville, Florida. In 1942, nine more Inshore Patrol Squadrons were established, all exclusively equipped with OS2N-1s built by the Naval Aircraft Factory.
The Kingfisher was widely used as a shipboard, catapult-launched scout plane on U.S. Navy battleships, heavy cruisers and light cruisers during World War II, as well as playing a major role in support of shore bombardments and air-sea rescue. Two examples showing the plane's rescue capabilities include the recovery of World War I ace Eddie Rickenbacker and his crew from the Pacific in November 1942 and LT John A. Burns' unique use of the aircraft in April 1944 to taxi airmen rescued from the Truk Lagoon to the submarine USS Tang which was serving rescue duty near the atoll on that date. In all, LT Burns rescued 10 survivors on two trips and was awarded the Navy Cross for his efforts.
Australia received 18 Kingfishers from a batch of aircraft ordered by the Dutch East Indies that was diverted to Australia in 1942. They were initially used as training aircraft for pilots destined for flying boats, but in 1943, they were used to equip No. 107 Squadron RAAF, which carried out convoy escort duties until disbanded in October 1945. One Kingfisher was used in support of the Australian National Antarctic Research Expedition in 1947–48.
Throughout its U.S. Navy service, the OS2U and even its predecessor, the Curtiss SOC Seagull served much longer than planned, as the planned successor, the Curtiss SO3C Seamew, suffered from an insufficiently powerful engine which was a complete failure. The OS2U was only slowly replaced in the latter stages of World War II with the introduction of the Curtiss SC Seahawk, the first examples reaching the U.S. Navy in October 1944.
Initial production variant as the prototype but powered by a 450 hp (336 kW) Pratt & Whitney R-985-48, 54 built.
Production variant with minor equipment changes and powered by a 450 hp (336 kW) Pratt & Whitney R-985-50, 158 built.
Based on the 02SU-2 with self-sealing fuel tanks, armour protection, two .30 cal (7.62 mm) guns (dorsal and nose mounted), and able to carry 325 lb (147 kg) of depth charges or 100 lb (45 kg) bombs, powered by a 450 hp (336 kW) Pratt & Whitney R-985-AN2 engine, 1006 built.
Two aircraft converted with narrow-chord and high-aspect ratio wings, also fitted with full-span flaps. Not developed.
Naval Aircraft Factory built OS2U-3 with a 450 hp (336 kW) Pratt & Whitney R-985-AN-2 or -AN-8 engine, 300 built.
At least eight Kingfishers survive in collections of historic aircraft around the world:
5985 - Whale World, Albany, Western Australia. It is also waiting "to be restored." Originally built for Netherlands Navy in Dutch East Indies, it was transferred to the RAAF in 1942, serving with Seaplane Training Flight (later 3 OTU) and 107 Sqn before being sold as war surplus in 1945.
5925 - Museo Nacional Aeronáutico y del Espacio de Chile, Santiago.
1368 (marked #60, painted as 0951) - Obtained years ago from Mexico, this aircraft was previously displayed aboard the battleship USS Alabama (BB-60) and is now displayed inside the aircraft pavilion adjacent to the battleship in Mobile, Alabama. Unfortunately, the building and the aircraft sustained some damage from Hurricane Ivan in 2004.