In October 1933, the US Navy placed an order with Consolidated and Douglas for prototypes of new machines. The prototype constructed by Consolidated, designated XP3Y-1, became a flying boat built in the largest number of copies. The internal designation assigned to the structure by the company is Consolidated 28. The aircraft, just like its predecessor - P2Y - had a high wing system. The new design, however, uses a system of internal stiffening curvatures, which made the wing look like a free-bearing structure. The only exception was the two small, profiled supports on both sides of the plane, between the fuselage and the centre wing. As a result, version 28 was devoid of sources of additional aerodynamic drag, generated in earlier designs by struts and stiffening straps, which were the cause of lower flight parameters. Another aerodynamic innovation limiting drag was the use of stabilizing floats, which were folded up during flight to form a profiled wing tip. The hull with two redans was very similar to that of the P2Y, but in the 28 version it had a streamlined, cross-shaped self-supporting tail. The prototype was powered by two 836HP Pratt-Whitney R-1830-54 Twin Wasp engines, installed on the leading edge of the wing. The armament consisted of four 7.62 mm machine guns and a bomb load of up to 907 kg. The first flight took place on March 28, 1935, after which the XP3Y-1 was promptly handed over to the US Navy for operational evaluation. The tests proved the significant advantage of the P3Y-1 over the patrol flying boats used so far. The long range and improved properties when taking off from land-based airfields meant that the US Navy expressed interest in the further development of the structure so that it could be used as a patrol-bomber. Therefore, in October 1935, the prototype returned to the parent plant to continue construction work on it. They included i.a. development of new R-1830-64 engines with a capacity of 912HP. A redesigned vertical tail was also introduced and a new prototype, designated XPBY-1, was flew on May 19, 1936, and soon the serial PBY-1 began to be delivered to the US Navy. After minor changes, the planes ordered in July 1936 received the designation PBY-2, and the following PBY-3 and PBY-4 were fitted with the R-1830-66 (1014KM) and R-1830-72 (1065KM) engines, respectively. In April 1939, the last of the PBY-4 machines was returned to the production plants for the installation of a wheeled chassis. Such equipment made the plane amphibious, extending the possibilities of its use. This specimen, leaving the production plant in November 1939 after the modification was completed, received the designation XPBY-5A. Test flights confirmed the advantage of this version over the previous one. Therefore, the planes ordered by the US Navy as PBY-5 were equipped as amphibians in accordance with the PBY-5A standard. Intensive use led to the thought that the plane could have significantly improved characteristics by redesigning the fuselage. The necessary tests and design works were carried out by Naval Aircraft Factory and the next, last production version of Catalina was already called PBY-6A. Technical data (PBY-5A version): length: 19.46m, wingspan: 31.7m, height: 6.15m, maximum speed: 314km / h, rate of climb: 5.1m / s, practical ceiling: 4000m, range maximum: 4050 km, armament: fixed - 3 machine guns calibre 7.62 mm and 2 machine guns calibre 12.7 mm, suspended - up to 1814 kg of bombs.