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The B-29: America’s Flying Superfortress

We’ve discussed a lot of planes on this channel. Most of them accomplish some sort of historic feat for their time, only to be outdone by the next model. For the B-29, though, that’s not quite the case. Sure, later planes would fly faster and higher, and they would include more advanced designs and avionics, but no aircraft before or after has played such a significant role in world history. Though it initially looked like an expensive failure, the B-29 would become the deadliest airplane in human history within about one year of introduction, a title it still holds to this day. It played a leading role in the Pacific Theater, and it is the only plane ever to drop an atomic weapon on an enemy target. Let’s get started.

Pre-War Situation

In the years before World War Two, America’s primary strategic bomber was the Boeing B-17 Flying Fortress. Officially introduced in 1938, the Flying Fortress was a competent aircraft, capable of effective bombing campaigns throughout Europe. Of course, by 1938, Hitler’s aggression was an early indication of the likelihood of an upcoming war in Europe. In the far east, Japan was also acting aggressively, invading China from their position in Korea and eventually taking much of China’s northeast and east coast.

The American military was well aware of the likelihood of war in both Europe and the Pacific, even if the official policy was isolationism and neutrality. Still, it was clear to the Army Air Corps commanders that the B-17, though well-suited for combat in Europe, didn’t have the range to cover the vast distances in the Pacific theater. The B-17 maxed out at about 3,200 km (2,000 miles), but the Air Corps needed something with a capacity over 4,800 km (3,000 miles).

Due in large part to the influence of famed aviator Charles Lindbergh, the Air Corps issued a formal specification for a “superbomber” that could deliver 9,100 kg (20,000 lb) of bombs to a target 4,292 km (2,667 mi) away and at a speed of 640 km/h (400 mph). Several aviation manufacturers submitted proposals, but Boeing already had something in the works. They had begun exploring a similar project a year or two earlier.

Boeing presented their design, the Model 345, on May 11th, 1940. By the end of that year, the Air Corps requested three flying prototypes with full airframes and assigned the project the designation XB-29. In 1941 the US officially entered WW2, officially upping the urgency of the project. The Army Air Force, which had just been formed from the AAC earlier that year, liked what they saw in the early stages of the XB-29’s development, and they ordered 500 aircraft in January of 1942. 

Aside from the “superbomber” specifications, the plane would need a state-of-the-art weapons system and a fully-pressurized cabin, something that had never been incorporated into a bomber. In fact, the first pressurized airplane was introduced just a few years before the B-29 project began. However, pressurizing a bomber was a much more challenging task, as the plane would need a weapons bay with doors that could open mid-flight while maintaining pressure throughout the cabin.

Boeing knew from the start that these requirements were all doable, but the main question was whether it could be completed on the AAF’s ambitious timeline. If you’ve seen many of our videos about airplanes, you may have noticed that their development can take over a decade from ideation to official introduction. Under less pressing circumstances, the B-29 would’ve taken at least five years to produce. Instead, Boeing had to mass-manufacture the aircraft while fine-tuning it and working out the kinks. As World War Two progressed, the need became more and more apparent.

Production Issues

Boeing partnered with two other manufacturers, Bell and Martin, to build the Superfortresses at 4 major factories throughout the US, in Washington, Kansas, Georgia, and Nebraska. The first prototype made its maiden flight on September 21st, 1942, taking off from Boeing Field near Seattle. The aircraft boasted what would become the B-29’s signatures— a wide 43 meter (141 ft) wingspan, a fuselage with a circular cross-section, and a stepless cockpit design. The craft was 30 meters long (99 ft), with a fuselage large enough for 11 crew members and an armament bay in the belly. The flight went smoothly, but it wasn’t exactly a great indicator of the plane’s ability. The prototype didn’t include any armament system, making the aircraft much lighter and easier to get off the ground.

The second prototype, fitted with a Sperry defensive armament system, made its first test flight on December 30th of ’42. Shortly after takeoff, though, the plane’s engine caught fire, and the flight was immediately halted. Just two months later, the same prototype took off from Boeing Field for a fully-manned test-flight, with disastrous results. Once again, the plane’s engine caught fire, but this time there wasn’t time to land safely. In fact, the crew contained the engine fire, but a separate malfunction caused a fire inside the plane’s fuel tank. It crashed a short distance away, killing all eleven men on-board and 21 civilians on the ground. 

The primary cause of these early disasters seemed to be the plane’s Wright R-3350 Duplex-Cyclone radial engines. You see, immediately after takeoff, most planes are fighting to gain altitude, but with the B-29, the struggle was reaching a fast enough airspeed. Radial engines require a lot of airflow to keep them cool, and the plane’s slower speed meant that the engines received less airflow, overheated, and caught fire. While the engine problem wouldn’t be totally solved until after the war, a handful of interim measures were put in place to ensure that the plane flew without catching fire. The most critical engineering change was to place cuffs on the propeller blades, which directed cold air into the engines’ intakes and then into the exhaust valves. Pilots were instructed to delay their ascent, instead maintaining level flight after takeoff until the plane reached a good cruising speed. While the B-29’s max velocity was about 575 km/h (357 mph), the pilots needed to hit 300-350 km/h (around 200 mph) before an ascent.

While the engine problems were the most pressing, the early Superfortresses faced enough mechanical issues to keep most of them on the ground. In late 1943, around 100 B-29s had been delivered to AAF bases around the US, but only 15 were airworthy. Due to the intense production timelines, Boeing’s factories couldn’t update the earliest models with the latest specifications. Like we mentioned earlier, most planes have a long period of testing and modification before they’re ever delivered to the end-user, but the B-29 didn’t have that luxury— changes had to be made on the fly after delivery.

This became a problem in early 1944, as the AAF-contracted modification centers were not well-equipped to handle the workload and the scope of requirements. After all, Boeing factory workers were the only aircraft manufacturers with any experience building such an advanced aircraft. So, AAF General Hap Arnold took control of the production, recruiting 600 Boeing engineers from the Kansas factory to relocate to the modification centers. These engineers trained the mod-center workers to apply the most up-to-date alterations. Within three months of Arnold’s involvement, Boeing and the AAF had completed more than 150 Superfortresses, and the speed only increased from there. Once the design was finalized, the number of man-hours spent on a single craft fell from 150,000 to just 20,000. 

Early Deployment

Over the next two years, from ’44 to ’46, the four factories would churn out about 4,000 Superfortresses, with an additional thousand coming from two other manufacturers. However, before the B-29 was deployed in 1944, there were some questions about how exactly the aircraft would be used. Although the plane was inspired by the need for a long-range bomber in the Pacific, they were initially intended for use against Germany. There were no airfields in the UK with enough space for a group of B-29s, so they were planned for deployment to Egypt. However, it became clear that the more pressing matter would be Japan and the Pacific Front. To keep China engaged in the battle against Japan, President FDR pledged that American B-29s would bomb Japan by spring 1944. In return, Chinese leader Chiang Kai Shek agreed to grant the Americans access to airbases in China. 

The process of reaching those bases was long and complicated, though. The fully equipped B-29 has a range of about 5,200 km (3,250 mi), and the Americans didn’t presently have a foothold in the Asia-Pacific from which to run supply drops to the planes in China. Instead, the Superfortresses were based in British North India, where they had a steady flow of fuel and ammunition. In preparation for raids, the fleet would carry supplies over the Himalayas, or “The Hump,” to bases in southwest China from which they would take off for their bombing runs. The first official B-29 combat flight took place in June of 1944, as about 75 of the planes based in India went on a bombing run of Bangkok, which was under Japanese control.

Just ten days later, 68 B-29s took off from a base in Chengdu, China, for the first bombing raid on Japanese territory since the Doolittle raid of 1942. Most of these planes targeted Imperial Iron and Steel Works factories in Yawata, but the attack was an utter mess. One Superfortress was shot down with anti-aircraft guns, while two others were forced down or crashed. Perhaps more importantly, only one bomb accurately struck the target factory complex. This lack of accuracy would become a theme for the B-29 in the early months of operation.

At the time of these early flights, the Air Force was using a method called strategic bombing. Strategic bombing calls for high-altitude bombers to drop explosives on critical locations in a city, like the factory complex in Yawata. Other common strategic targets include water supplies or bridges. Not only could hitting a strategic target render a city incapable of supporting the war effort, but it would also spare civilian lives. This was the method employed throughout the western front, and the AAF tried to use it in Japan, but it wasn’t working. Despite double-checking every calculation, B-29 bombs consistently fell dramatically miles of their targets.

It took months of failures and research to discover just what was causing this imprecision. The B-29 was a high altitude bomber, regularly flying well over 9,710 m (31,850 ft). At the time, the Americans knew very little about the conditions at this altitude in Earth’s atmosphere. But they were about to discover something that the Japanese themselves had learned just twenty years earlier. About 9.5 km above Japan, winds regularly reached 400 km/h (250 mph)— this multi-direction jet stream made strategic bomb impossible. If the B-29s were going to successfully bomb Japan into submission, there would need to be some profound changes. 

Bombing Japan into Submission

Following the mostly failed sorties of late ’44 and early ’45, the AAF instituted two significant changes that completely altered the legacy of the B-29 and the direction of the war. 

First, air bases in China placed Japan barely within the range of the B-29’s 4,800 km (3,000 miles) radius— that may seem impossible if you look at a map, but keep in mind that Japan already occupied much of eastern China, and bombers needed fuel to safely return to base. To effectively bomb the entire country, the Americans would need runways much closer to the island nation. So, they moved into the Marianas islands, a remote archipelago about 2,500 km south of Tokyo. US forces took Saipan, Tinian, and Guam in the summer of 1944 and immediately built 5 large air bases there. Now, Japan’s population and industrial centers were all well within the range of a fully-armed B-29.

The other meaningful change was in the bombing tactics employed by the B-29s. Earlier, we discussed strategic bomb tactics and the complications caused by the Japanese jet stream. That was when legendary American Major General Curtis Lemay stepped in. Lemay was a notorious military innovator, and he implemented a shift from high-altitude strategic bombing to low-altitude firebombs. Incendiary raids began with the bombing of Kobe city on February 4th, 1945, and it immediately became clear that this new method would reap destruction unlike anything ever seen before. In fact, to this day, the firebombing of Tokyo on March 9th and 10th is still the deadliest bombing attack in human history, with an estimated 100,000 casualties in the space of 24 hours. Despite that fact, the firebombing of Tokyo would never be quite as infamous as the B-29s final major act of WW2— dropping the atomic bombs on Hiroshima and Nagasaki. 

In 1943, a physicist named Norman Ramsey, who was working on the Manhattan Project, was tasked with finding a plane capable of dropping the two massive bombs that his team had developed. The bomb designs were called the Thin Man, which was long and tubular, somewhat like typical explosives, and the Fat Man, which was ovular and rotund. Ramsey determined that the only airplane capable of carrying and dropping either bomb was the B-29, which was still incomplete. However, the job would require some modifications, so Ramsey collaborated with AAF General Hap Arnold to order a handful of specialized Superfortresses called Silverplates. These modified aircraft were stripped of the typical armaments found in B-29s to save weight for carrying the massive explosives. They also included fuel injectors, reversible props, and a special weaponeer station in the cockpit, which contained tools for monitoring the bomb’s condition before it was dropped.

After another year of development on the Manhattan Project, and with the Silverplate B-29s thoroughly tested, President Harry Truman made the order. On August 6th, 1945, Lieutenant Colonel Paul Tibbets flew a Silverplate called Enola Gay to drop the first atomic bomb, Little Boy, on Hiroshima. Three days later, the plane Bockscar dropped the Fat Man on Nagasaki. Less than a week later, the war with Japan was over. The B-29 had effectively ended the war with its months-long bombing of the Japanese mainland.

Post-WWII and Retirement

In the months following World War Two, the B-29 went from the war’s deadliest airplane to a PR tool and record marathoner. A handful of Air Force generals flew modified versions of the B-29 all over the world, regularly setting records for the longest nonstop flight which still stand today. In October of 1946, Colonel Clarence Irvine flew a B-29 over the polar ice cap from Oahu, Hawaii, to Cairo, Egypt, covering an astounding 9,422 miles in a single flight.

The Superfortress’s production was officially halted in 1946, as the final model rolled out of Boeing’s Seattle factory that year. But that was not the end of the B-29’s story. The Superfortress played a small role in the Korean War from 1950-53, but it became clear that the bomber was less suited for this type of warfare. North Korea had few clear targets, whether for strategic or firebombing. Plus, the USSR’s introduction of the MiG-15 presented the B-29 with a formidable interceptor. Still, B-29s flew 20,000 sorties and dropped 200,000 tonnes (180,000 tons) of bombs throughout the war, primarily flying at night to prevent interception.

After the Korean War, the B-29 gradually drifted into obsolescence. The Convair B-36 became the Air Force’s preferred long-range bomber, and the B-50 filled in the rest of the gaps, such as long-range recon and air-to-air refueling. Though originally planned as the B-29D, the B-50 included some critical changes that improved on its predecessor, especially the inclusion of a new engine and a thicker aluminium frame. While it’s often compared to the plane that spawned it, in reality the B-50 was a completely new plane that closely resembled the B-29. By 1955, though, the B-52 Stratofortress was introduced, effectively ending the involvement of the B-29 and its B-50 variant.

Legacy

All in all, the B-29 was a massive success and a considerable part of the American victory over Japan in World War Two. That may seem obvious in hindsight, but that certainly wasn’t always the case. When it was regularly catching fire and crashing, the B-29 looked like a massive waste of money. In fact, the B-29 project was the most expensive project of World War Two, with a total cost of 3 billion dollars, or 43 billion in current US dollars. In contrast, the Manhattan Project cost 1.9 billion, or about 63% of the cost of the B-29. The average cost of a single bomber was about 800,000 dollars or about 11 million in 2020. In the end, more B-29s were lost to mechanical failures than enemy fire.

The plane was so impactful in the bombing of Japan that the USSR even copied its design. When a handful of US pilots couldn’t retreat to American bases after bombing raids, they continued northward and landed in Siberia. Instead of returning the plane to the Americans, the Russians took it apart piece by piece and did their best to reverse engineer it, coming up with the Tupolev Tu-4. 

Aside from its role in the war, the B-29 will be remembered for its innovations— the pressurized cabin, the remote-controlled gun system, and stepless cockpit, to name a few. Its influence can be clearly seen in the early Cold War bombers, notably the B-52, which took the Superfortresses dramatic wide, thin wings and turned it up a notch. 

Today, twenty-two B-29s are preserved across the world, all but two within the US. Among this total are the Bockscar and Enola Gay, the two planes that dropped the atomic bombs on Japan. Two B-29s are still in flying shape today, one, called FIFI, which belongs to the Commemorative Air Force, and another, called Doc, which belongs to Doc’s Friends. You can catch a glimpse of them at air shows around the states and even buy a ticket to ride inside.

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