Competitors to the B-29 from southern California: Lockheed XB-30, Douglas XB-31, and Consolidated B-32 Dominator

The Boeing B-29 Superfortress long-range strategic bomber is best known in the annals of military history as the US heavy bomber that carried out carpet-bombing raids on Japan in the final months of the Pacific theater of World War II and brought about the ultimate finale to human history's most destructive conflict by dropping atomic bombs on Hiroshima and Nagasaki, which forced Japan to surrender for the first time in its military history on August 14, 1945. However, the B-29 was not a standalone development when it came to fulfilling military aviation requirements for a long-range heavy bomber with greater range and bombload than the B-17 or B-24. In southern California, three aircraft manufacturers --- Consolidated, Douglas, and Lockheed --- came out with heavy bomber designs to compete with the B-29, but only one was selected for full-scale development and became the Consolidated B-32 Dominator. Since the B-32 entered production but only got as far as limited full-scale production before war's end, I am opting to give a comprehensive synopsis of the rival designs to the B-29 envisaged in southern California, including the B-32.

The Boeing B-29 Superfortress, which along with the Consolidated B-32 Dominator won the R-40B competition of 1940.

On November 10, 1939, two months after Germany invaded Poland, US Army Air Corps General Henry "Hap" Arnold requested authorization to contract with major aircraft companies for studies of a Very Long-Range (VLR) bomber to strike enemy targets over greater distances than the B-17 Flying Fortress and B-24 Liberator. In December, the USAAC issued the VLR "superbomber" requirement for a new strategic bomber with a top speed of 400 mph (640 km/h) and able to carry 20,000 lb (9,100 kg) of bombs over a range of 2,667 miles (4,292 km). On January 29, 1940, the War Department issued Request for Data R-40B based on this requirement and circulated it to Boeing, Consolidated, Douglas, and Lockheed, and on April 8, Specification XC-218A was issued which also required additional defensive armament, armor, and self-sealing tanks. 

Left: A wind tunnel model of the Lockheed XB-30 heavy bomber derivative of the Constellation airliner.
Right: Side view of the Douglas XB-31 project, designated Model 332F by Douglas (courtesy of Alan Griffith).

Three companies based in southern California submitted bids for the R-40B competition. Consolidated's design, the Model 33, was a scaled-up B-24 Liberator derived from the company's initial LB-25 design study of late 1939/early 1940, while Lockheed submitted the L-117 (Model 51-58) derivative of the Constellation airliner with a length of 104 feet 8 in (31.91 meters), a wingspan of 123 feet (37.50 meters), a wing area of 1,646 square feet (153 m²), empty and gross weights of 51,616 lb (23,462 kg) and 85,844 lb (39,020 kg) respectively, and armament comprising ten .50 in (12.7 mm) machine guns (eight in four fuselage turrets and two in a single nose turret) and one 20 mm cannon in a remote-controlled tail turret. Douglas envisaged a series of design studies under the internal designation Model 332, all of them resembling a scaled-up A-20 Havoc and distinguished by their tail empennage layouts and engines; the Model 332F submitted for the R-40B was 88 feet 8.5 in (27.04 meters) long with a wingspan of 140 feet 6 in (42.82 meters), a wing area of 1,780 square feet (165.54 square meters), gross and maximum take-off weights of 106,994 lb (48,532 kg) and 120,000 lb (54,432 kg) respectively, and armament comprising seven pairs of 0.50-in (12.70 mm) machine guns (four in pairs facing rearwards in the rear of the outboard engine nacelles, and three in dorsal and ventral turrets below the fuselage) and one 20 mm cannon in the tail. On June 27, 1940, the Lockheed L-117, Douglas Model 332F, and Consolidated Model 33 submissions were designated XB-30, XB-31, and XB-32 respectively, and like the Boeing Model 345 (which became the XB-29), they were powered by four Wright R-3350 Duplex Cyclone radial piston engines. Some older sources (e.g. Francillon 1979; Jones 1984) identify the Douglas Model 423 intercontinental bomber project of October 1941 as the XB-31, but as noted by Buttler and Griffith (2015), the Model 423 was conceived in response to the 1941 intercontinental bomber competition won by the Northrop XB-35 and Convair B-36 Peacemaker and thus never received a military designation.

Top left: The first XB-32 prototype (serial number 41-141) taxiing at Lindbergh Field, San Diego, early September 1942
Top right: The second XB-32 prototype (serial number 41-142) in flight, July 1943
Bottom: The third XB-32 prototype (41-18336) (note the newly installed tall vertical stabilizer that offered better directional stability compared to the initial twin-fin tail empennage and B-29 type vertical stabilizer) during a test flight with the propellers of the port engines feathered in mid-1944.. 

In July 1940, the USAAC announced that the XB-29 and XB-32 had won the R-40B competition, the XB-30 and XB-31 submission having been withdrawn due to Lockheed and Douglas being preoccupied with production of the A-20, P-38, Hudson, and DC-3. On September 6, 1940, a contract was signed for two XB-32 prototypes (serial numbers 41-141/142) at the same time that two XB-29 prototypes were ordered, and a third prototype (serial number 41-18336) was added in November. Mock-ups of the XB-32 was built in late December and later inspected and approved January 6, 1941, after a few structural changes, and thirteen YB-32s (serial numbers 42-108471/108484) were ordered on June 30. The XB-32 was 82 feet 1 in (25.02 meters) long with a wingspan of 135 feet (41.15 meters), a height of 20 feet 10 in (6.35 meters), a wing area of 1,422 square feet (132.1 m²), a gross weight of 101,662 lb (46,113 kg), a top speed of 376 mph (605 km/h), and twelve crewmen, with armament comprising fourteen 0.50 in (12.70 mm) machine guns and two 20 mm cannons (eight in the upper and lower gun turrets, two in the wing's leading edges outboard of the propellers, and four 0.50 in [12.70 mm] machine guns and two 20 mm cannons at the rear of the outboard engine nacelles in rearward firing positions and controlled by aiming stations in the fuselage and tail). It was similar to the B-24 Liberator in its tail empennage, high-mounted Davis-type wing, and twin bomb bays covered over by roll-up doors, but differed in having a cylindrical fuselage, larger wing, and a stepped cockpit nose section. The first XB-32 prototype was rolled out on September 1, 1942, making its first flight from Lindbergh Field, San Diego, on September 7, two weeks before the B-29. However, a number of developmental problems with the fire control system and in February 1943 the YB-32 contract was canceled, but a month later, an order was placed for 300 production B-32s (serial numbers 42-108471/108770) to be built at the Consolidated plant in Forth Worth, Texas.* The first XB-32 crashed shortly after takeoff on May 10 due to a flap malfunction, killing the test pilot and injuring six crewmen, dealing a setback to the B-32 flight test program. The second XB-32 prototype, which first flew on July 2, had modified rudder tabs, a pressurized cabin,  remote-controlled retractable gun turrets in the dorsal and ventral positions, and a manned tail turret, and it was transferred to Muroc Army Air Field (now Edwards Air Force Base) in February 1944 for acceptance tests after thirty test flights. The third XB-32 prototype first flew on September 17, 1943 and differed from the first two prototypes in having ten machine guns in the nose, dorsal, ventral, and tail turrets. Due to longitudinal stability problems after 25 test flights, this aircraft was fitted with the single vertical stabilizer designed for the B-29 in November 1943 and first flown with this new tail empennage on January 6, 1944, but this vertical tail was deemed to offer marginal stability, so an even taller vertical stabilizer measuring 19 feet 4.28 in (5.9 meters) high was installed on the third XB-32, which first flew with this vertical tall in the spring of 1944. The B-32 was initially named Terminator in late 1943 at the behest of Consolidated, but the US Army Air Force's Aircraft Naming Board changed the name to Dominator; the State Department eventually had the B-32 revert to its initial name for the sake of "political correctness", but the name Dominator tends to persist in most aviation literature for the B-32.

* After the cancellation of the YB-32 contract, the serial numbers allocated to the YB-32s were re-used for the first 13 production B-32s.

The first production B-32 Dominator (serial number 42-108471) in flight over Fort Worth, Texas, August 1944 

In June, the US Army Air Force increased the number of B-32s on order to 1,213 aircraft, including a batch of 500 B-32-1-CO aircraft (serial numbers 44-90486/90985) to be built at the Convair factory in San Diego, and it changed the B-32's official name to Dominator. The first two production B-32s, of which the first flew on August 5, 1944, were initially fitted with the vertical stabilizer from the B-29, but the latest single vertical stabilizer built for the third XB-32 was eventually fitted to these aircraft. The production B-32 had a ten-man crew, a maximum bombload of 20,000 lb (9,071 kg), a maximum range of 4,421 miles (7,114 km), and defensive armament comprising ten 0.50 in (12.70 mm) Browning M2 machine guns in five power-operated turrets (four in two Martin turrets on the top of the fuselage, four in Sperry ball turrets on the nose and in the tail, and two in a retractable belly turret). Deliveries of the B-32 to US Army Air Force began in September 1944, but by then the B-29 had begun combat missions over Japan, and although the B-32 had been touted by the USAAF as a back-up in the event that the favored B-29 failed, the success made by Boeing in helping the B-29 overcome engine troubles during flight testing as well as delays and deficiencies in the B-32 program prompted several USAAF officials to recommend that the B-32 program be cancelled outright. By the end of 1944, only fourteen B-32s were delivered to the USAAF, and they even experienced mechanical malfunctions, while complaints were made about faulty workmanship on some of the delivered aircraft. However, in December, Brigadier General Donald Wilson recommended that despite these difficulties it would be unwise to abandon the B-Dominator program until a full set of tests had conclusively demonstrated its unsuitability, and no final decision about the Dominator's future be made until after the completion of service tests, allowing for the crew training program should continue. From January to March 1945, forty B-32s (serial numbers 42-108485/108524) were delivered to the USAAF without gun turrets or bombing equipment for B-32 crew training  and officially designated TB-32. Prospective B-32 pilots underwent 50 hours training in TB-32s and co-pilots received 25 hours of flight time and 25 hours of observer training. The first B-32 to be built in San Diego was flown on March 17, 1945, but following Nazi Germany's surrender on May 8, orders for the B-32 were reduced to 214 aircraft from Fort Worth. Lieutenant General George C. Kenney of the Fifth Air Force had been anxious to acquire B-29s, but when his requests were turned down on the grounds that the B-29 was urgently needed elsewhere, he started requesting B-32s instead. On March 27, 1945, General Henry "Hap" Arnold approved Kenney's request and authorized the USAAF to carry out comprehensive combat tests of the B-32 Dominator. Three B-32s were dispatched to the 386th Bombardment Squadron of the 312th Bombardment Group based on Luzon, Philippines, on May 24-25, 1945, to begin combat testing, and on May 29 the B-32 carried out its first combat mission when two of the three B-32s (42-108529 and 42-108532) attacked a Japanese supply depot in Luzon's Cayagan Valley, followed by a series of strikes in June on targets in Formosa (now Taiwan) and Hainan Island (B-32 serial number 42-108528 did not take part in the May 29 mission because it made an abort during take-off). The B-32s encountered no real enemy opposition except for inaccurate enemy flak, and they returned to their base safely. 

Convair B-32 Dominator Hobo Queen II (serial number 41-108578), which carried out the last combat mission by an Allied aircraft in World War II.

Following the success of the first B-32 combat mission, the 386th Bombardment Squadron made plans to transition from the A-20 Havoc to the B-32, and the 387th Bombardment Squadron began following suit, with eventual plans to relocate the 312th Bombardment Group to Okinawa. Before the conversion could be carried out, however, the dropping of the atomic bombs on Hiroshima and Nagasaki in early August 1945 led to the 312th BG being moved to Okinawa immediately, and six more B-32s joined the squadron on Okinawa a few days later. Combat operations continued in spite of the de-facto cease-fire that had been called following the bombing of Nagasaki, and August 17, four B-32s carrying out a photographic reconnaissance mission over Tokyo to confirm Japan's surrender were fired upon on by radar-directed flak and attacked by Japanese fighters, but suffered only minor damage, claiming three air-to-air kills (two A6M Zeroes and one N1K-J Shiden-Kai). On August 18, the B-32 Hobo Queen II (serial number 42-108532) and a second B-32 (serial number 42-108578) were attacked by Japanese fighters, and tail gunners claimed three air-to-air kills (two A6M Zeroes and one N1K-J Siden-Kai), but Japanese fighters heavily damaged 42-108578, killing Sergeant Anthony Marcione and wounding two more men, including photographer Staff Sergeant Joseph Lacharite. Nonetheless, 42-108578 returned to its base in Okinawa, and the Japanese fighters downed by the B-32s on August 18 constituted the last Axis warplanes to be shot down by American (and more broadly Allied) combat aircraft in World War II.  The last B-32 photographic reconnaissance mission was conducted on August 28, during which two B-32s were destroyed in separate accidents, with 15 of the 26 crewmen killed. Two days later, the 386th Bombardment Squadron stood down from operations, and with the end of the Pacific theater of World War II, unfulfilled B-32 orders were cancelled on September 8 and production of the B-32 halted on October 12. By this time, 115 production B-32s had been delivered (114 from Fort Worth and one from San Diego), while twelve additional aircraft (42-108585/108594, 44-90487/90488) were completed but not delivered, and no fewer than 49 B-32s were nearing completion at Fort Worth. All the B-32s that were operational as well as the undelivered aircraft were flown to storage at a disposal and reclamation center in Walnut Ridge, Arkansas, in 1946, and most of them were scrapped by 1947. One B-32 (serial number 42-108474) was set aside for future display at the National Museum of the US Air Force in Dayton, Ohio, but this plan never materialized and the aircraft was scrapped at Davis-Monthan Air Force Base in Tucson, Arizona, in August 1949. Nevertheless, a few B-32 components survive today, including a B-32 nose turret in storage at the Paul Garber Restoration Facility of the Smithsonian Institution at Suitland, Maryland, another B-32 nose turret on display at the Minnesota Air and Space Museum, and a static test wing panel from a B-32 erected as a monument to aviation pioneer John J. Montgomery on a hill near San Diego.

Two advanced B-32 (Model 33) studies that never were: a cutaway view of a four engine maritime reconnaissance project dated April 28, 1945 (left) and an artist's conception of early B-32 airliner proposal conceived in December 1941 (right)   

In an interesting footnote, several unbuilt variants of the B-32 Dominator were envisaged by Convair for maritime patrol and transport, along with a proposed turboprop-powered version. As early as mid-1941, a passenger airliner variant of the B-32 was conceived with a crew of six and accommodations for 78 passengers in daytime operations or 34 passengers at night, and in 1943, two military transport versions of the B-32 were devised, one which looked like a slightly smaller Convair XC-99 and which would have been used as either a troop transport, a hospital MEDEVAC aircraft, a paratrooper aircraft, or a cargo transport for carrying howitzers, aircraft, military jeeps, anti-tank guns, and/or ammo trucks. The latter design was also envisaged in September 1943 as a 58 passenger airliner, and design studies were also conducted for a B-32 escort aircraft (similar to the Boeing XB-40 and the Consolidated XB-41), a variant powered by four General Electric TG-100 (T31) turboprops, a twin-engine B-32 proposal, and a four-engine maritime reconnaissance B-32 variant armed with ten 0.50 in (12.70 mm) machine guns (four in the forward and aft top fuselage turrets, two in a retractable bottom fuselage turret, and four in the nose and tail turrets) and provisions for photoflash bombs, mines, or depth charges in the bomb bay. However, due to delays in development and production of the B-32, none of these proposals ever materialized.

Although the Consolidated B-32 Dominator is one of the lesser-known American bomber aircraft of World War II due to the fact that it was intended as a back-up in the event of the failure of the B-29, only to nearly arrive too late for the war due to the success of the B-29, it nonetheless holds the honor of undertaking the last combat mission by an Allied aircraft in World War II, considering that the rival B-29 was instrumental in forcing Japan to surrender after repeatedly refusing to do despite defeats at Iwo Jima and Okinawa.       

References:

Andrade, J. M., 1979. US Military and Aircraft Designations and Serials since 1909. Leicester, UK: Midland Counties Publications.

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: Fighters, Bombers, and Attack Aircraft, 1937-1945. Manchester, UK: Crecy Publishing. ISBN 978-1906537487.

Francillon, R. J., 1979. McDonnell Douglas aircraft since 1920, Volume 1. London, UK: Putnam Publishing.

Jones, L.S., 1984. U.S. Bombers: 1928 to 1980s. Fallbrook, CA: Aero Publishers.

Wolf, W., 2006. Consolidated B-32 Dominator: The Ultimate Look: from Drawing Board to Scrapyard. Atglen, PA: Schiffer Publishing.