The PB3Y: Consolidated's unbuilt successor to the PB2Y Coronado

 The Consolidated PBY Catalina and PB2Y Coronado are well-documented in the literature on US naval aircraft of World War II as the poster boys of US anti-submarine warfare campaigns during the war, namely the Battle of the Atlantic and the sinking of Japanese submarines in the Pacific theater. Also of note is the fact that Consolidated (later Consolidated Vultee, then Convair) built several B-24 Liberator bombers for the US Navy as the PB4Y-1, from which a dedicated maritime patrol landplane, the PB4Y-2 Privateer, was developed. However, virtually lost in talk of US patrol aircraft development in World War II is one Consolidated project for a giant maritime patrol flying boat, the PB3Y. For a long time, the story of the PB3Y has been an enigma because of the length of time it was designed and developed but without ever leaving the drawing board. Now, thanks to my analysis of Consolidated's evolving priorities in military aircraft development from the late 1930s until the Japanese attack on Pearl Harbor as well as company documents, it is now possible to reconstruct the history of the design and development of the PB3Y.

A wind tunnel model of the initial Model 30 flying boat (XPB3Y-1) with a single vertical stabilizer

In January 1937, Consolidated began design studies for a new flying boat as a long-term replacement for its upcoming and yet-to-be flown PB2Y Coronado under the company designation Model 30. The first design of the Model 30, labeled 'XPB3Y-1' in company documents, retained the single vertical stabilizer initially fitted to the XPB2Y-1 but was 75 percent larger and heavier than the PB2Y-1, with a wingspan of 180 feet (54.86 meters), and power was supplied by four R-2800 radial piston engines. Accommodations were provided for four crewmen (pilot, co-pilot, navigator, and communications operator), and defensive armament included remote-controlled nose, dorsal, and tail turrets as well as a manually-controlled turret behind the step. Consolidated's informal use of the XPB3Y-1 label for the initial Model 30 proposal probably reflected anticipation of a future requirement for a new-generation long-range patrol flying boat because a Convair tailless land-based patrol bomber study of the 1940s was informally dubbed 'XP5Y-1' by Convair (the P5Y designation was formally used for the turboprop-powered Convair Model 117 flown in 1950, but that's another story). In fact, in May 1937, the US Navy issued requirement SD116-16 for a long-range patrol flying boat to replace the PB2Y Coronado, and because the Boeing 319 derivative of the 314 passenger flying boat but also the company's 320 twin-hull flying boat and the Martin Model 160A  were also conceived in the early 1937, it seems plausible that the initial Model 30 design was conceived along with the Martin Model 160A and Boeing 319 and 320 for the SD116-16 requirement.  

An artist's concept of a revised Model 30 design (XPB3Y-1) with twin vertical stabilizers from the project documents.

In January 1938, the US Navy tweaked the parameters of requirement SD116-16 to produce an updated operational requirement, SD116-19. In response, Consolidated revisited the Model 30 by having the design revised to incorporate the twin-rudder tail empennage eventually used for the PB2Y and a cockpit partially blending with the nose, and several Model 30 iterations were proposed with radial and V-cylinder engines. The Model 30/XPB3Y-1 design conceived in February 1938 was powered by four Wright R-3350 Duplex Cyclone radial piston engines and had a wingspan of 190 feet (57.91 meters), a wing area of 3,200 square feet (297.60 square meters), an empty weight of 57,258 lb (25,972 kg), a gross weight of 124,700 lb (56,563 kg), a top speed of 246 miles per hour (396 km/h), and a range of 8,200 miles (13,194 km). Fifteen crewmen were carried, and defensive armament was to consist of ten .50 caliber machine guns and one 20 mm cannon, housed in remote-controlled turrets on the nose, top waist, and tail, and manually-controlled turrets on the sides of the fuselage and behind the step, while 36,000 lb (16,330 kg) of bombs were carried. The gunners were also placed in the leading edges of the wing fillet, and passageways led outboard of the engines to two cupolas with guns that could fire up or down. Like the PB2Y, the Model 30 proposal of early 1938 had floats that could be retracted in flight after takeoff. The 190-foot span Model 30/XPB3Y-1 competed with rival Martin Model 170 Mars (originally Model 160B) (which was also powered by Duplex Cyclones but featured a slightly larger wingspan of 200 feet (60.96 meters) and six .50 caliber machine guns) and the Boeing 324 (also derived from the Boeing 314) designs for the SD116-19 requirement. On August 23, 1938, the Navy selected the Martin Model 170 over the Consolidated and Boeing designs, giving it the designation XPB2M-1. 

An artist's rendering of the Model 34/XPB3Y-1, late 1941

Although the Model 30 design of February 1938 had lost out to the Mars, protracted construction of the prototypes of the PB2M led Consolidated to propose a slightly scaled-down Model 30 in 1941 with the company designation Model 34. The overall design of the Model 34 was similar to the Model 30 design of 1938 as well as the PB2Y, and it had a wingspan of 169 feet (51.5 meters), a length of 104 feet 8 in (31.90 meters), a wing area of 2,600 square feet (241.80 square meters), a gross weight of 121,500 lb (55,111 kg), four Pratt & Whitney R-2800 Double Wasp radial piston engines, a top speed of 241 mph (388 km/h), and a range of 5,000 miles (8,045 km). A total of nine crewmen were to be carried, and armament comprised 20,000 lb (9,072 kg) of bombs and eight .50 caliber machine guns arranged in pairs in Erco nose and top ball turrets, along with twin waist blisters and a Convair-designed tail turret, while seal-sealing fuel tanks and armor protection were provided. The US Navy formally accepted the Model 34 design for full-scale development in late 1941, probably viewing it as assurance in case the Martin PB2M Mars ran into developmental problems, and on April 2, 1942, the aircraft was formally designated XPB3Y-1 and and one prototype (BuNo 32386) ordered the same day. A full-scale mockup of the XPB3Y-1 was inspected at the Consolidated Vultee factory in San Diego in early October, but a month earlier, on September 9, Isaac Laddon asked the US Navy to cancel the XPB3Y program because of his company's preoccupation with development of the B-32 Dominator, the B-36 Peacemaker, and PB4Y-2 Privateer. The Navy agreed, and the XPB3Y-1 program was axed on November 4. The cancellation of the XPB3Y-1 was perfectly timed, because the Martin PB2M Mars had taken flight a few months earlier, eventually being developed into the JRM cargo transport flying boat after the US Navy pronounced the patrol bomber flying boat concept obsolete.  

As a side note, in November 1941 Consolidated conducted design studies for a commercial version of the Model 34/XPB3Y-1 design conceived in September. The passenger flying boat variant of the Model 34 would have carried 77 passengers in day accommodations or 41 passengers in a night flight sleeper configuration, with a crew of 15 (including two stewards and one stewardess) and a maximum range of 3,700 miles (5,955 km), and comparisons of the commercial Model 34 were made with the Boeing 314 and Martin 130. However, like the XPB3Y-1, the Model 34 commercial flying boat design would never progress beyond the drawing board.

References:

Bradley, R., 2010. Convair Advanced Designs: Secret Projects from San Diego 1923-1962. North Branch, MN: Specialty Press.

Buttler, T., and Griffith, A., 2015. American Secret Projects 1: Fighters, Bombers, and Attack Aircraft, 1937 to 1945. Manchester, UK: Crecy Publishing.

Norton, B., 2012. American Bomber Aircraft Development in World War 2. Hersham, UK: Midland Publishing. ISBN 978-1-85780-330-3.

Wagner, R., 2004. American Combat Planes of the 20th Century: A Comprehensive Reference. Reno, Nevada: Jack Bacon & Co. ISBN 0-930083-17-2.