“What was the reason for the B-36 Peacemaker not being used in combat?”
The simple answer is that the Consolidated (later Convair) B-36 arrived too late to be used in WWII and was too valuable to the Strategic Air Command (SAC) as its only strategic intercontinental bomber to be deployed tactically during the Korean War. The advent of the all-jet B-52 intercontinental bomber quickly led to the B-36’s retirement, never having seen combat. This brief explanation doesn’t fully capture the eight years of tumultuous development the program underwent, buffeted by the shifting priorities of wartime.
The B-36 Peacemaker was initially envisioned in 1940 as an intercontinental bomber to strike Germany if the UK fell to German forces. When the UK’s survival became apparent, the B-36’s priority was reduced, ranking below the Boeing B-17, Consolidated B-24, Boeing B-29 and Northrop XB-35. (The XB-36 was a backup to the XB-35.) The B-36’s priority fluctuated, rising when Japan seemed poised to overrun China in mid-1943, and falling as the Allies’ prospects improved. Ultimately, development delays of the B-36 and its P&W R-4360 engines, along with the pressing demands of other war programs, meant the B-36 was introduced after WWII had ended. It should be noted that the USAAF received information about the A-bomb in mid-July 1943. Had this knowledge been available earlier in the XB-36’s development, the program might have been given greater priority and the B-36 might have been ready to drop the A-bomb in Aug-45.
Here’s a timeline to contextualize the B-36’s development:
- 1939-1940: The fall of France and the Battle of Britain raised the possibility of the UK’s surrender and the USAAC losing airfields in the UK, leaving no practical means to attack Germany.
- 1940-1941: The Axis powers seemed on the verge of dominating Eurasia. While Germany was halted at the English Channel, they advanced in the eastern Mediterranean and North Africa. Japan had taken over a third of China and aimed for French Indochina and the Pacific Rim, potentially isolating the US from bases outside the Western Hemisphere.
- Nov-1940: P&W began design studies for the R-4360 engine.
- 11-Apr-41: The USAAC releases request for proposal for an intercontinental bomber, but the proposal requirements far exceed the technological capabilities of the time. Max speed of 450 mph, 275 mph cruising speed, service ceiling of 45,000 ft, and maximum range of 12,000 miles at 25,000 ft.
- 19-Aug-41: Proposal requirements are reduced to increase probability of success. 240 to 300 mph cruise speed, service ceiling of 40,000 ft, maximum range of 10,000 mi, effective combat radius of 4,000 mi, and maximum bombload 10,000 lb
- 16-Oct-41: Consolidated Vultee Aircraft Corporation (later Convair) wins the competition to develop two prototype (only one built) bomber.
- 25-Apr-42: The first flight of the R-4360 prototype engine
- July-42: USAAF inspects the completed XB-36 mockup and the program nearly cancelled due to weight and performance concerns
- 17-Aug-42: First ETO combat of USAAF B-17 heavy bombers (Rouen-Sotteville railway yards).
- 9-Oct-42: First ETO combat of USAAF B-24 heavy bombers (Lille, France)
- R&D work on the XB-36 continued slowly because Consolidated had been directed to prioritize construction of the B-24, which had far greater practical value in attacking Germany.
- Spring 1943: With China appearing on the verge of collapse, the USAAF feared that Operation Matterhorn, the plan to use B-29s to bomb Japan from bases in central China, might have to be abandoned. As a result, the longer-range B-36 appeared to be the only viable means of striking the Japanese home islands.
- 19-Jun-43: When Consolidated suggests that a production contract would be necessary in order to accelerate XB-36 development, Gen Arnold directs the awarded of a contract for 100 B-36 production models. Under the new schedule, a deadline was set to have the XB-36 fly by Sep-44, with delivery of production models to begin by Aug-45. (This is the date of the A-bomb was dropped on Hiroshima and Nagasaki.)
- Circa mid-July 43: Gen Leslie Groves briefs Gen Hap Arnold on the Manhattan Project and requests ballistic (drop) testing of Project’s proposed “Thin Man” bomb shapes. Because of “need-to-know” secrecy, it is highly possible that this is the first Arnold knew of the A-bomb.
- 23-Jul-43: USAAF sends a letter of intent for the production contract
- Mid-1944, the B-36 is seriously behind schedule because of development delays in the R-4360 engines and delays in XB-36 wind tunnel testing.
- The B-36 project’s sense of urgency had dramatically changed as B-29s are delivered to the CBI, and new bases are planned in the Marianas Islands.
- 5-June-44: First China-Burma-India Theater (CBI)-based B-29s raid on Japan
- 9-Jul-44: Mariana Islands captured putting Japanese home island within range of the B-29.
- 24-Nov-44: First Marianas-based B-29s raid on Japan
- Jan-45: First production R-4360-4 delivered.
- 20-Aug-45: XB-36 completed
- 2-Sep-45: Japanese formally surrenders
- 8-Aug-46: XB-36 first flight
- Oct-46: R-4360-41A with 3,500 bhp delivered (replacing 3,000 bhp R-4360-25 in XB-36)
- Jun-48: First operational B-36A delivered to SAC’s 7th Bomb Group
- 25-Jun-50 to 27-Jul-53: Korean War
- 1951: Delivery of first combat ready aircraft (B-36D)
- 1953: Boeing B-47 Stratojet jet bomber becomes fully operational
- 1955: Boeing B-52 Stratofortress intercontinental bomber becomes operational.
- 12-Feb-59: B-36 retired as a strategic bomber by USAF
The reason the B-29 had a higher manufacturing priority than the B-36 was likely due to the high risk associated with the B-36 program because of its size (2/3 longer than the B-29) and the likelihood that the B-36 would not be ready before the end of the war.