The PBY Catalina was the definitive air-sea rescue aircraft of the 1930s and 1940s. It was equipped with depth charges, bombs, torpedoes, and machine guns, and its job was to seek out the enemy at sea.

PBY is literally: P, patrol; B, bomber. Y, Consolidatedís manufacturer identification.

The US Navy contracted Consolidated Aircraft and Douglas Aircraft Corporation in October 1933 to build competing prototypes for a patrol flying boat with greater range and load-carrying capability than the Consolidated P2Y and Martin P3M. The prototypes were designated XP3Y-1 and XP3D-1 respectively. Only a single prototype of the Douglas design was built.

Consolidated's XP3Y-1, was further developed and eventually became the most extensively built flying boat in aviation history. Consolidatedís design had a parasol-mounted wing and was identified as the Model 28. This new design introduced internal wing bracing and resulted in the wing being a virtual cantilever, except for two small streamline struts between hull and the wing center on either side. This design made the Model 28 the first aircraft free of the multiplicity of drag-producing struts and bracing wires and increased its performance over earlier designs.

Stabilizing floats that could be retracted in flight to form streamlined wingtips made for another aerodynamic innovation. The two-step hull design was similar to that of the P2Y, but instead of strut-braced twin fins and rudders mounted high on the tailplane, the Model 28 had a clean cruciform tail unit which was a cantilever structure.

The powerplant for the prototype comprised two 825 hp (615 kW) Pratt & Whitney R-1830-54 Twin Wasp engines mounted on the wingís leading edges.

Armament comprised four 0.30 in (7.62 mm) machine guns and up to 2,000 lb (907 kg) of bombs.

The XP3Y-1 had its first flight on 28 March 1935 after which it was transferred to the US Navy for service trials. The XP3Y-1 soon proved to have significant performance improvements over current patrol flying boats. The US Navy requested further development in order to bring the aircraft into the category of patrol-bomber, and in October 1935 the prototype was returned to Consolidated for further work. The work included installation of 900 hp (671 kW) R-1830-64 engines. For the redesignated XPBY-1, Consolidated introduced redesigned vertical tail surfaces. XPBY-1 had its maiden flight on 19 May 1936, during which a record non-stop distance flight of 3,443 miles (5,541 km) was achieved.

The XPBY-1 was delivered to US Navy Squadron VP-11F in October 1936. Second to be equipped was Squadron VP-12, which received the first of its aircraft in early 1937.

The second production order was placed on 25 July 1936. Minor equipment changes brought the designation PBY-2.

PBY-3s were ordered on 27 November 1936 with 1,000 hp (746 kW) R-1830-66 Twin Wasp engines, and PBY-4s were ordered on 18 December 1937 with 1,050 hp (783 kW) R-1830-72 Twin Wasp engines. All but the earliest models of the PBY-4s had large transparent blisters over the waist gun positions instead of sliding hatches, and these became a characteristic feature of all subsequent production aircraft.

In April 1939 the first example of the PBY-4 production aircraft was returned to the company for installation of wheeled landing gear in tricycle configuration so that these aircraft could operate in amphibian mode. This aircraft was completed in November 1939 and emerged with the designation XPBY-5A. The 33 aircraft outstanding on US Navy contracts for PBY-5s were completed as amphibians. An additional 134 PBY-5As were contracted on 25 November 1940. The US Navy received these aircraft towards the end of 1941.

By mid-1938 14 US Navy squadrons were equipped with various configurations, including five based at Pearl Harbor and three at Coco Solo. By the time the USA was involved in World War II 21 squadrons were equipped; 16 with PBY-5s, two with PBY-4s and three with PBY-3s.

The Soviet Union had shown an interest in the aircraft and an order for three aircraft and the negotiation of a licence to build the type in Russia resulted. When these three machines were delivered they were accompanied by a team of Consolidated engineers who assisted in establishment of the Russian production facilities. This aircraft, designated GST, was powered by two Mikulin M-62 radial engines with a power rating of 900-1,00 hp (671-746 kW). The first of these GSTs was put into service towards the end of 1939. It is estimated that the hundreds more were put into service with the Soviet navy. Russia also received under Lend-Lease 137of the PBN-1 Nomads built by the NAF and 48 PBY-6As.

The British Air Ministry purchased a single aircraft for evaluation purposes, the Model 28-5. The aircraft was flown across the ]]Atlantic Ocean]] to the Marine Aircraft Experimental Establishment at Felixstowe, Suffolk, England in July 1939. With the outbreak of war being anticipated, the trials were terminated prematurely, and an initial 50 aircraft were ordered under the designation Catalina I. These aircraft were similar to the US Navy's PBY-5s save for the installation of British armament. The name Catalina had been used by Consolidated prior to the British order, and was eventually adopted by the US Navy on October 1 1941.

Initial deliveries of the RAF's Catalinas began in early 1941 and these were entered service with Nos. 209 and 240 Squadrons of Coastal Command. In all, nine squadrons of Coastal Command were to be equipped with the ship. An additional 12 squadrons served overseas. The total acquisition totalled approximately 700.

Soon after the receipt of Britain's first order for production aircraft, Consolidated received a French purchasing mission which, in early 1940, ordered 30 aircraft. Allocated the company's identification of Model 28-5MF, none of these were delivered before the collapse of the French resistance.

Other orders received around the same time covered 18 aircraft for the Royal Australian Air Force, and 48 ordered by the Dutch for use in the Netherlands East Indies. Canada had its own close associations with the Catalina, both as a manufacturer and customer. Under an agreement reached between the Canadian and US governments, production lines were laid down in Canada, by Boeing Aircraft of Canada at Vancouver, and by Canadian Vickers at Cartierville.

The final construction figure is estimated at around 4,000 aircraft, and these were deployed in practically all of the operational theaters of World War II. Catalina served with distinction and played a prominent and invaluable role in the war against the Japanese. This was especially true in the first year, when Catalinas and Boeing B-17 Fortresses were the only two aircraft with the range necessary for these operations. As a result they were used in almost every possible military role until a new generations of aircraft became available.

With the end of the war, flying boat versions were quickly retired from the US Navy, but amphibious versions remained in service for several years. The Catalina subsequently equipped the world's smaller armed services, in fairly substantial numbers, into the late 1960s.