The Grumman J2F Duck (company designation G-15) is an American single-engine amphibious biplane. It was used by each major branch of the U.S. armed forces from the mid-1930s until just after World War II, primarily for utility and air-sea rescue duties. It was also used by the Argentine Navy, who took delivery of their first example in 1937. After the war, J2F Ducks saw service with independent civilian operators, as well as the armed forces of Colombia and Mexico. The J2F was an improved version of the earlier JF Duck, the main differences being a longer float and a more-powerful engine (900 horsepower versus 775). Development The J2F-1 Duck first flew on 2 April 1936, powered by a 750 hp (559 kW) Wright R-1820 Cyclone, and was delivered to the U.S. Navy on the same day. The J2F-2 had an uprated Wright Cyclone engine of 790 hp (589 kW). Twenty J2F-3 variants were built in 1939 for use by the Navy as executive transports with plush interiors. Due to pressure of work following the United States entry into the war in 1941, production of the J2F Duck was transferred to the Columbia Aircraft Corp of New York. They produced 330 aircraft for the Navy and U.S. Coast Guard. If standard Navy nomenclature practice had been followed, these would have been designated JL-1s, but it was not, and all Columbia-produced airframes were delivered as J2F-6s. Several surplus Navy Ducks were converted for use by the United States Air Force in the air-sea rescue role as the OA-12 in 1948. Design The J2F was an equal-span single-bay biplane with a large monocoque central float which also housed the retractable main landing gear, a similar design to the Leroy Grumman-designed landing gear first used for Grover Loening's early amphibious biplane designs, and later adopted for the Grumman FF fighter biplane. The aircraft had strut-mounted stabilizer floats beneath each lower wing. A crew of two or three were carried in tandem cockpits, forward for the pilot and rear for an observer with room for a radio operator if required. It had a cabin in the fuselage for two passengers or a stretcher. The Duck's main pontoon was blended into the fuselage, making it almost a flying boat despite its similarity to a conventional landplane which has been float-equipped. This configuration was shared with the earlier Loening OL, Grumman having acquired the rights to Loening's