The B-36, which became the most controversial American combat type since the DH-4, began its career before the attack on Pearl Harbor. The world’s largest bomber owed its size to the desire to achieve intercontinental range, for in 1941 the United States faced the possibility that Nazi Germany would control all of Europe, and that only bases in America would be available for strikes at enemy strategic targets.
A design competition for a heavy bomber was opened on April 11, 1941. That specification was refined in August to include a 10,000-pound load carried halfway across a 10,000-mile range, and Consolidated Aircraft submitted designs dated September 19. A proposal with six pusher engines seemed superior to Boeing and Douglas offerings, and a contract approved November 15, 1941, ordered two XB-36 prototypes to be delivered about May 15 and November 15, 1944.
The project was moved from San Diego to Fort Worth, Texas, in August 1942, but progress was slow due to the company’s concentration on B-24 production and B-32 development. General Arnold saw that the B-36 might be needed for attacking Japan if bases near enough for the B-29 strikes were not secured. The company’s president complained that it was difficult to get subcontractors for a two-plane order; but they would be interested if large-scale production was promised. A letter of intent for 100 B-36 bombers was issued July 23, 1943, at which time company officials planned to fly the XB-36 in September 1944 and begin production deliveries in March 1945, with 29 expected by the end of August.
Engineering changes like the shift from twin tails to a stronger single fin in October 1943, the change to the NACA 63 airfoil, and the complexity of the huge aircraft caused more delay. By the time a firm contract was approved on August 19, 1944, expecting delivery for 100 B-36s to begin in August 1945, capture of the Marianas Islands, from which B-29s could bomb Japan, had made the B-36 unnecessary for that war. Again the B-36 program was neglected in favor of the B-32.
Defensive armament designed for the XB-36 included four remote-controlled retractable turrets and a radar- directed tail turret. Each upper and lower forward turret had two 37-mm guns and each upper and lower rear turret had four .50-caliber guns, like those planned for the XB-32. The tail turret, like the B-29, would have one 37-mm and two .50-caliber guns.
This system was replaced in production aircraft by a new arrangement planned in 1944. The most formidable armament of any warplane would have sixteen 20-mm guns, with 9,200 rounds, paired in eight General Electric remote-controlled turrets. Computing sights at blisters in the nose and six side spots aimed the front turret and six retractable turrets which disappeared under sliding panels, while APG-3 radar aimed the tail guns.
A new pilot’s canopy, raised over the a redesigned flight deck was deck, was chosen in October 1944 for the second prototype, which was designated YB-36. The prototype’s single 110-inch wheels on each side required runways twice as thick as usual, so only Fort Worth and two other fields could handle the test aircraft. Production models would spread the weight over four 56-inch wheels on each side, along with the dual nose wheels, so the B-36 could use most B-29 bases.
A major problem was the loss of speed due to added weight and engine problems. Guaranteed top speed in April 1944 of 369 mph at 30,000 feet was reduced to 347 mph in July 1945 and to 323 mph in the July 1946 estimate. But the lifting power of six 3,000-hp R-4360-25 radials and the enormous bays were undeniable: 72 1,000-pound bombs could be carried half-way for 4,600 miles, or 20 500-pound bombs for 9,360 miles.
Japan’s surrender, and the new importance the atomic bomb gave strategic bombing, once again revived the giant bomber program. An air staff conference on August 9, 1945, recommended that four B-36 groups be included in the postwar Air Force.
Delayed by manpower shortages, and late engine delivery, the XB-36 made its first flight nearly five years after it had been ordered, instead of the 30 months originally planned. Beryl A. Erickson and G. S. Green piloted the takeoff on August 8, 1946, of the heaviest, 100 tons, and largest plane ever to fly up to that time.
A new canopy, raised over the flight deck, and the four-wheel main landing gear was installed on the first aircraft from the production line, which was designated YB-36A and first flew on August 28, 1947, in unfinished condition. It was flown from Fort Worth to Wright Field two days later to be stripped and demolished in static tests.
The second prototype, the YB-36, had the new nose, but retained the large single main wheels. Delayed by the installation of equipment, it flew on December 4, 1947, and better dual superchargers immediately improved high altitude performance. Yet the bomber’s large size and slow speed raised doubts of its ability to survive in enemy air space.
Doubts about the B-36s were shared by the first SAC commander, General George C. Kenney, who in December 1946 had suggested cancellation of B-36 production in favor of the faster and smaller B-50. In that case, strategic bombing would require advanced bases or aerial refueling. Increased B-36 over-the-target speed was needed, so in March 1947 Convair proposed the installation of Pratt & Whitney’s proposed experimental VDT engines with tractor propellers.