Subsequently, in the United States during the 1920s and 1930s, Sikorsky developed a series of outstanding commercial flying boats.1 In June 1935, the U.S. Navy ordered a prototype for a new patrol bomber from Sikorsky and in July 1936, from Consolidated. These were four-engine flying boats with long ranges and large payloads. The Sikorsky aircraft was designated XPBS-1 by the Navy.
On 9 September 1937, the XPBS-1 made its first flight, with the Consolidated XPB2Y-1 flying the following 17 December. After extensive evaluations, the Navy initiated production of the Consolidated design.2
The Sikorsky flying boat had a high wing mounting four radial engines, tall tail fin, and fixed, outboard floats. It was the first U.S. military aircraft to be fitted with a nose as well as tail gun turret, plus it had provisions for two waist guns. The turrets were to mount a single, hand-operated .50-caliber machine gun; the two waist positions were for single .30-caliber guns. As a patrol bomber it was intended to carry 4,000 pounds of bombs.