The Boeing B-29 Superfortress is famous on many counts, but chief among them is that it is the only aircraft ever to have delivered nuclear bombs in war. This American, four-engine, propeller-driven heavy bomber was operated mainly during the Second World War and the Korean War. It was designed for high-altitude strategic bombing, but was far more deadly when utilised for low-altitude night incendiary bombing. It was built with the European theatre in mind, but was finally deployed in the Pacific theatre and used to mount devastating attacks against Japan.

What ultimately turned out to be one of the most important aircraft programmes of World War II began in June 1939, when the United States (US) Army Air Corps felt the need for a new long-range bomber. Boeing had been working on an advanced bomber design and submitted its proposal for the B-29 in early 1940. It received an initial contract in September 1940 and the first prototype of the B-29 flew on September 21, 1942. Meanwhile the US had entered World War II in December 1941.

The B-29’s design was extremely advanced for the period, yet it went from drawing board into battle in under four years. It had a long, narrow, high-aspect ratio wing with large Fowler flaps, allowing it to cruise at high speeds at high altitudes, but maintain comfortable handling characteristics during takeoff and landing. It was powered by four Wright R-3350 Duplex-Cyclone twin-row, supercharged, air-cooled, radial aircraft engines with 18 cylinders each and rated at 2,200hp each.

The B-29 had a cruise speed of 190 knots, maximum speed of 310 knots and range of 2,820nm. It was the first bomber to house its 11-man crew in pressurised compartments which gave it a high operating ceiling of 31,850 ft. When it entered production, it was one of the world’s largest aircraft and undoubtedly the heaviest. It had a dual-wheeled tricycle landing gear. Quite amazing for the 1940s was an analogue computer-controlled fire-control system that allowed a gunner and a fire-control officer to direct four remote machine gun turrets.

Four main-assembly factories and thousands of subcontractors were involved in the B-29’s manufacture. However, it soon became apparent that the bomber’s highly advanced design, coupled with its hurried development and intense pressure for rapid production, would create problems. In December 1942, a test flight of a prototype had to be abruptly terminated due to a serious engine fire. And in February 1943, the same aircraft again experienced engine fire and crashed, killing Boeing test pilot Edmund Allen, his 10-man crew and 21 people on the ground. Of the first 96 aircraft built, only 16 were rated as flyable. Still with the War in a critical phase the pressure to get the B-29s into combat continued and its teething troubles were gradually resolved.

In December 1944, the US began employing B-29s based at the Mariana Islands to bomb Japan. The initial high-altitude, supposedly precision bombing missions, were largely ineffective. The prevailing jet streams rendered the bombing computers highly inaccurate and cloud cover meant that visual target acquisition was rarely possible. In March 1945, Major General Curtis LeMay changed the strategy to low-level attacks with incendiary bombs. These night-time raids carried out by hundreds of B-29s, destroyed much of Japan’s industrial and economic infrastructure. In fact, a single attack on the night of March 9, 1945, in which 334 B-29s participated, dropped 1,667 tonnes of incendiary bombs on Tokyo, destroying 41 square kilometres and killing an estimated 1,00,000 civilians. It remains the single deadliest bombing operation ever, deadlier than the nuclear attacks that came just months later.

A B-29 named ‘Enola Gay’, piloted by Colonel Paul Tibbets, dropped the first atomic bomb on Hiroshima on August 6, 1945. Three days later, another B-29 named ‘Bockscar’, piloted by Major Charles Sweeney, dropped the second bomb on Nagasaki. The devastation cause by these two attacks is too well known to need repetition.

When production ended in 1946, 3,970 B-29s had been built. Each aircraft was hugely expensive and the programme ultimately cost $3 billion, equivalent to around $48 billion today. As against this, the Manhattan Project that developed America’s nuclear bomb cost just $1.9 billion. While the B-29 initially failed as a conventional high-altitude daylight strategic bomber, it met significant success as a low-altitude night-time incendiary bomber, perhaps because the Japanese air defences were weak. Its place in history is assured mainly because of its record as the only bomber to have delivered a nuclear weapon in anger. In fact no other aircraft of the period could have brought the proud Japanese practically to their knees. The last B-29 retired from squadron service in the USAF in September 1960.