With the requirement for a patrol flying boat to offer greater range and load-carrying capability than the Consolidated P2Y or Martin P3M, which were in service in the early 1930s, the US Navy contracted Consolidated and Douglas in October 1933 to build competing prototypes. Designated XP3Y-1 and XP3D-1 respectively, only a single prototype of the Douglas design was built. Consolidated's XP3Y-1, however, was to be developed to become the most extensively-built flying boat in aviation history.
Consolidated identified their design to meet the US Navy's requirement as the Model 28 and this, like the P2Y which preceded it, had a parasol-mounted wing. However, in the new design the introduction of internal bracing resulted in a wing which was virtually a cantilever, except for two small streamline struts between hull and wing centre-section on each side. Thus the Model 28 was free of the multiplicity of drag-producing struts and bracing wires which had limited the performance of earlier designs. Another innovation adding to aerodynamic efficiency was the provision of stabilising floats which, when retracted in flight, formed streamlined wingtips. The two-step hull design was very 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. Powerplant of the prototype comprised two 825 hp (615 kW) Pratt & Whitney R-1830-54 Twin Wasp engines mounted on the wing leading edges. Armament comprised four 0.30 in (7.62 mm) machine guns and up to 2,000 lb (907 kg) of bombs. First flown on 28 March 1935, the XP3Y-1 was soon transferred to the US Navy for service trials, which confirmed a significant improvement in performance over the patrol flying boats in service. Its extended range and improved load-carrying capability caused the US Navy to request further development to bring this new aircraft into the category of a patrol-bomber, and in October 1935 the prototype was returned to Consolidated for the necessary work to be carried out, including installation of the 900 hp (671 kW) R-1830-64 engines which had been specified for the 60 PBY-1s (a patrol-bomber designation) which had been ordered on 29 June 1935. At the same time redesigned vertical tail surfaces were introduced and the XPBY-1, as this prototype was redesignated, flew for the first time on 19 May 1936. After completing its trials, during which a record non-stop distance flight of 3,443 miles (5,541 km) was achieved, this aircraft was delivered to US Navy Squadron VP-11F during October 1936, in which month the first of the PBY-1s began to reach the squadron. Second to be equipped was Squadron VP-12, which received the first of its aircraft in early 1937.
Minor equipment changes brought the designation PBY-2 for the second production order placed on 25 July 1936, while the PBY-3s ordered on 27 November 1936 and PBY-4s on 18 December 1937 had 1,000 hp (746 kW) R-1830-66 and 1,050 hp (783 kW) R-1830-72 Twin Wasp engines respectively. All but the first examples of the PBY-4s introduced large transparent blisters over the waist gun positions, in place 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 so that these aircraft could operate as amphibians, thus making them far more versatile. Of tricycle configuration, the landing gear featured a nosewheel retracting into the hull beneath the flightdeck, and the main units (mounted externally on each side of the hull beneath the wing) folding to fit into small recesses. This aircraft, when completed in November 1939, emerged with the designation XPBY-5A. Testing confirmed, if confirmation was needed, the very considerable advantages of the amphibian configuration. The 33 aircraft outstanding on US Navy contracts for PBY-5s were completed as PBY-5A amphibians, and an additional 134 PBY-5As were contracted on 25 November 1940. First US Navy Squadrons to be equipped with this version were VP-83 and VP-91, which received them towards the end of 1941.
Extensive service use of the PBYs had suggested that the hull would benefit from hydrodynamic improvement, and the Naval Aircraft Factory had undertaken the necessary research and development work to achieve this end, receiving an order for 156 of these modified aircraft under the designation PBN-1 Nomad. This course was adopted in order that the design changes would not interfere with the major production coming from Consolidated. When the final production version was built by Consolidated between April 1944 and April 1945, the NAF's improvements were incorporated in a model designated PBY-6A. In addition to the hydrodynamic refinement of the hull, the NAF had also improved the lines of the wingtip floats, introduced taller vertical tail surfaces, increased fuel tankage, strengthened the wings for higher gross weight, and updated the electrical system.
From mid-1937 PBYs were introduced rapidly into service with the US Navy, and by mid-1938 14 squadrons were equipped, including five based at Pearl Harbor and three at Coco Solo; by the time the USA became involved in World War II some 21 squadrons were equipped, 16 with PBY-5s, two with PBY-4s and three with PBY-3s.
Before this, however, interest shown by the Soviet Union resulted in an order for three aircraft and the negotiation of a licence to build the type in Russia. When these three machines were delivered they were accompanied by a team of Consolidated engineers who assisted in establishment of the Russian production facilities. Designated GST, these production aircraft were powered by Mikulin M-62 radial engines, a developed version of the M-25 licence-built Wright Cyclone which had a power rating of 900-1,00 hp (671-746 kW). The first of these GSTs began to appear in late 1939, and an unspecified number, certainly running into several hundreds, were built during the war for service with the Soviet navy. In addition to these home-built examples, Russia also received under Lend-Lease 137 of the PBN-1 Nomads built by the NAF and 48 of the PBY-6As.
European interest started with purchase by the British Air Ministry of a single aircraft for evaluation, this being identified by Consolidated as the Model 28-5. Flown across the Atlantic, the craft was allocated to the Marine Aircraft experimental Establishment at Felixstowe, Suffolk in July 1939. The outbreak of war anticipated the termination of the trials, but with little doubt of the excellence of the design, a first batch of 50 was ordered under the designation Catalina I, these being generally similar to the US Navy's PBY-5s except for the installation of British armament. The name Catalina had been used by Consolidated prior to receipt of the British order, and was not adopted by the US Navy until 1 October 1941.
Initial deliveries of the RAF's Catalinas began in early 1941, these entering service with Nos. 209 and 240 Squadrons of Coastal Command. They were subsequently to equip nine squadrons of Coastal Command, as well as an additional 12 squadrons serving overseas. Not surprisingly, this involved the acquisition of a considerable number of these aircraft, totalling approximately 700. The figure is only an approximate one because records vary by two or three aircraft. With the exception of 11 PBY-5As which were diverted to Britain from a US Navy order, all were non-amphibious flying boats. They comprised 100 Catalina Is equivalent to the Navy's PBY-5, 225 Catalina 1Bs (PBY-5B), 36 Catalina IIAs (PBY-5), 11 Catalina IIIs (PBY-5A), 97 Catalina IVAs (PBY-5), 193 Catalina IVBs which were built by Boeing Aircraft of Canada as PB2B-1s and were generally similar to the non-amphibious PBY-5As, and 50 Catalina VIs, Boeing-built PB2B-2s which had the taller vertical surfaces first introduced on the NAF PBN-1. No Catalina Vs served with the RAF, this designation being allocated for potential supplies of NAF PBN-1s, none of which in the event were sent to Great Britain.
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 foreign orders received at about the same time covered 18 aircraft for the Royal Australian Air Force, and 48 ordered by the Dutch government for use in the Netherlands East Indies. Of these latter, 36 had been delivered before the Japanese invasion, and only nine were flown off before capture, being used as initial equipment for No. 321 Squadron in Ceylon.
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. Tooling for production was started in 1941: Boeing's first PB2B-1 flew on 12 May 1943, that of Canadian Vickers more than a month earlier, on 3 April 1943.
Boeing production totalled 362 aircraft, these comprising 240 PB2B-1s supplied to Australia, Britain and New Zealand; 50 PB2B-2s for Britain; 17 non-amphibious Catalinas for the RCAF, and 55 amphibians which, in Royal Canadian Air Force service, were designated Canso. Aircraft produced by Canadian Vickers totalled 379 equivalent to the PBY-5A, of which 149 were supplied to the RCAF. From the balance of 230 the US Navy planned to acquire 183 under the designation PBV-1A; in fact the US Navy received none of these, all of them being supplied to the USAAF which had previously acquired 56 PBY-5As as a direct transfer from the US Navy and which it designated OA-10. These were used throughout World War II for search and rescue missions, some carrying air-dropped lifeboats beneath each wing. The 230 aircraft built by Canadian Vickers were designated OA-10A in USAAF service, and the final production aircraft to be received were 75 PBY-6As built by Consolidated, and which were designated OA-10B.
Because there is no record of the number of Catalinas built in Russia as GSTs, it is impossible to quote any figure for total production. The best one can do is to estimate the final construction figure as one around 4,000. What is certain is the excellence of this most attractive aircraft, which was deployed in practically all of the operational theatres of World War II. It served with distinction and, in the war fought against the Japanese where the battle area was largely sea and islands, played a prominent and invaluable role. This was especially true in the first year, when Catalinas and Boeing B-17 Fortresses were the only two aircraft with the essential tribute of long range. As a result they were used in almost every possible military role until a new generation of aircraft became available in the Pacific theatre: such a capability meant that the Catalina rapidly gained a reputation for ability and reliability which is remembered to this day.
With the end of the war, flying boat versions were quickly retired from the US Navy, but amphibious versions remained in service for a few years: they subsequently equipped the world's smaller armed services, in fairly substantial numbers, into the late 1960s.