B-29 Superfortress: The Birth of Long-Range Bombing and Its Global Impact

The Boeing B-29 Superfortress was an aircraft that dominated the skies during the final stages of World War II, representing a technological revolution and permanently redefining the doctrine of strategic bombing. More than just a weapons platform, the B-29 became a tangible symbol of a nation's industrial might, engineering audacity, and the brutal realities of war. As the main element of the final and most devastating offensive against Japan on the Pacific Front, this aircraft pushed the boundaries of conventional warfare and ultimately ushered in the nuclear age by enabling the dropping of atomic bombs on targets in Japan, without distinction between military and civilian, thus opening a new chapter in human history. This study analyses the comprehensive story of the B-29 Superfortress, from its conceptual birth to its post-war legacy, and its profound and lasting impact on aviation and military history.

Cover image Boeing B-29s of the 468th Bombardment Group on a bombing mission over Rangoon, Burma, 22 March 1945. Photo USAF

Part I: From Concept to Reality: The Birth of the B-29 Superfortress

The development of an aircraft is not merely a process of technical advancement, but also a complex reflection of the geopolitical and strategic imperatives of its era. The emergence of the B-29 Superfortress clearly demonstrates the strategic importance the United States placed on a long-range, high-altitude air power capable of striking potential enemies far from its own territory, as it stood on the brink of a global conflict. This section examines the strategic imperatives, engineering pursuits, and technological advances that transformed the Superfortress from initial blueprints on paper into a reality in the skies.

1.1. Strategic Necessity and Origins

In the late 1930s, as the global political atmosphere became increasingly tense, the United States Army Air Corps (USAAC) began to feel the need to go beyond the capabilities of its existing bomber fleets. Even powerful aircraft of the era, such as the B-17 Flying Fortress, lacked the intercontinental range that a future war might demand. In this context, a new generation of bomber aircraft concept, classified as ‘very heavy’ (very heavy) bomber aircraft concept emerged. The first steps were quite modest; in March 1938, the USAAC asked Boeing to investigate the possibility of pressurising the B-17's cabin. This request was indicative of how constrained military aviation budgets were at the time. Indeed, in 1938, the total budget allocated for all items of military aviation was less than the cost of a single armoured battleship. However, this small step sowed the seeds for the strategic bomber of the future.

1.2. Design Evolution: Concepts on Paper

The path to the B-29 was paved with a series of evolutionary design experiments. Boeing engineers pushed the limits of existing technology and frequently experimented with radical new ideas, gradually approaching the final Superfortress form.

First Steps (Models 316 & 322):

These initial concepts, which emerged in 1938, were derived from the XB-15 and B-17 designs, respectively. Model 316 was a modernised version of the XB-15, while Model 322 was an improved version of the B-17. Although both offered innovations such as pressurised cabins and tricycle landing gear, the increase in performance was negligible. These designs were shelved before being formally submitted to the USAAC, as it was thought that the minor improvements they would bring would not justify the production costs.

Radical Approaches (Models 333 - 334):

In early 1939, engineers experimented with bolder concepts to maximise aerodynamic efficiency. Model 333 proposed tandem (back-to-back) liquid-cooled Allison engines, one propulsive and one retractable, on each wing. Models 333-A, 333-B, and 334, however, utilised horizontal engines that were completely embedded within the wing, a concept that existed only on paper at the time. These designs encountered practical engineering challenges in the pursuit of aerodynamic cleanliness. Cooling the tandem engines was difficult, while the embedded engines weakened the wing structure, reduced fuel capacity, and created maintenance difficulties.

Breakthrough Design (Model 334-A):

Designed in July 1939, the Model 334-A is considered the first ‘ancestor’ of the B-29. This design overcame the ‘high wing loading phobia’ that had been a taboo in the aviation industry until then.

Engineers questioned the old belief that high wing loading inevitably meant dangerously high landing speeds. Their main challenge was to design a wing flap that would both assist take-off and reduce landing distance. With its long, narrow wings and an unprecedented wing loading of 47 pounds per square metre, the Model 334-A promised a revolutionary range of 5,333 miles. This was a turning point for strategic aviation.

Impact of the War (Models 341 & 345):

With the outbreak of war in Europe, military requirements changed rapidly. The USAAC now demanded not only long range, but also greater bomb load, sealed fuel tanks, and much more powerful defensive armament. These demands fundamentally altered the design parameters. Model 341, designed in August 1939, was a response to these new requirements. However, additional demands in March 1940 led to the creation of Model 345. The addition of leak-proof tanks alone added 3,000 pounds of extra weight, and with the additional fuel required to carry this weight, the aircraft's total weight increased exponentially. The Model 345, with its increased weight, reinforced structure, and remotely controlled turrets, took shape as the concept closest to the final XB-29.

1.3. Fundamental Engineering Tests and Innovations

The elements that made the B-29 an aircraft far ahead of its time were the innovative solutions engineers found to the enormous challenges they faced.

High Wing Loading and Flap Design:

To overcome the high landing speed problem caused by high wing loading, Boeing engineers developed enormous Fowler flaps with an area equal to one-fifth of the wing area (332 square feet). These flaps increased the wing's lift by one-third, enabling the B-29 despite its enormous weight.

Engine and Cooling Problems:

The Wright R-3350 Duplex Cyclone engine was ‘the most common cause of maintenance headaches and catastrophic failures’ from the beginning to the end of the programme. These engines were particularly prone to overheating in the rear cylinder banks. Numerous attempts were made to solve the problem, including increasing airflow with propeller shrouds, adding special baffles to the engine compartments, and increasing oil flow. However, the chronic overheating problem was not fully resolved until the post-war B-50 programme switched to more powerful Pratt & Whitney R-4360 engines.

Pressurised Cabin System:

Pressurisation technology pioneered in the Stratoliner passenger aircraft was adapted for the B-29 to enable the crew to perform their duties for hours at altitudes above 30,000 feet without relying on oxygen masks. The nose, middle (gunner) and tail sections of the aircraft were pressurised separately. A cylindrical tunnel passing over the unpressurised bomb bays allowed the crew to crawl between the front and middle sections. This design maintained the aircraft's structural integrity while also allowing crew mobility.

Remote-Controlled Defence System:

To minimise aerodynamic drag at high speeds, traditional manned turrets were abandoned. Instead, a remote-controlled defence system developed by General Electric and controlled by a central computer was installed. Gunners identified targets using periscope-like sights at different points on the aircraft, while the central computer automatically calculated factors such as the target's speed, distance and bullet ballistics to direct the turrets at the target. The brain of this system was a sophisticated analogue computer, an engineering marvel of the pre-transistor era, consisting of a combination of electrical, electronic (vacuum tube) and mechanical equipment. This system allowed a gunner to control multiple turrets, enabling the concentration of defensive fire at a single point.

These engineering breakthroughs made the B-29 not just an extension of existing bomber aircraft, but also the beginning of a completely new era in strategic aviation.

Part II: Wartime Production and ‘Birth Pangs’

The B-29 programme was not only the production of a new and complex aircraft, but also a massive national mobilisation that pushed the limits of America's industrial capacity. The urgency of the war necessitated that the programme proceed with unstoppable momentum, despite unfinished designs and countless unresolved technical issues. The tragedies during the prototype phase, production bottlenecks, and the struggle to get the first aircraft combat-ready reveal just how severe the Superfortress's ‘birth pangs’ were.

2.1. Industrial Mobilisation: Building a Giant

The production of the B-29 was too large an undertaking for a single company to handle. Therefore, the programme was distributed among multiple prime contractors, including Boeing (Wichita, Kansas, and Renton, Washington), Bell Aircraft (Marietta, Georgia), and Glenn L. Martin (Omaha, Nebraska).

In addition to these main factories, numerous subcontractors, including Chrysler, Goodyear, Cessna, and Hudson, produced various components of the aircraft. To standardise and accelerate production, the ‘Multi-line Production’ (Multi-line Production) system developed by Boeing's production chief, H. Oliver West. Under this system, the aircraft was divided into five main components (nose, forward fuselage, mid-wing section, rear fuselage, and tail), each of which was nearly completed on its own assembly line and then rapidly assembled in the final stage. This modular approach allowed even inexperienced workers to be involved in the complex production process.

2.2. Prototype and Test Flights: Tragedy and Perseverance

The testing process for the XB-29 prototypes was a painful period filled with high hopes and tragic losses.

First Flight and Engine Problems:

The first XB-29 (41-002), commanded by Boeing's legendary test pilot Edmund “Eddie” Allen, made a successful maiden flight on 21 September 1942. However, this positive start was followed by chronic problems with the R-3350 engines. By December, ‘16 engine changes, 19 exhaust system revisions and 22 carburettor changes’ had been required in just 27 hours of flight time. The engines were constantly overheating and frequently catching fire.

The Tragedy of the Second Prototype:

The programme's darkest day came on 18 February 1943. The second XB-29 prototype (41-003), carrying Eddie Allen and a 10-person test crew, made an emergency landing shortly after take-off due to a fire in engine number 1. As Allen attempted to bring the burning aircraft back to Boeing Field, the fire spread to the wing spar, compromising the wing's structural integrity. The out-of-control aircraft crashed into a meat packing plant in Seattle. Allen and his entire crew, along with 20 people on the ground, were killed in the crash, bringing the total death toll to 31. The professional and psychological impact of this tragedy was devastating. Eddie's Flight Test Chief and chief pilot, Al Reed, was the only person who had flown a B-29 after the crash; he never flew again after the accident.

Investigation and Findings:

This horrific crash sent shockwaves through the B-29 programme. A committee chaired by Senator Harry Truman immediately launched an investigation. The investigation concluded that concluded that the engine manufacturer, Wright Aeronautical Company, had delivered ‘substandard or defective engines’ to the military under pressure to increase production speed. This tragedy led to extensive and urgent changes in engine cooling systems, fuel lines, and fire prevention procedures.

The image above is a cross-section drawing of the B-29 Superfortress

2.3. ‘The Kansas Battle’: Preparing Aircraft for Combat

The first B-29s rolling off the production lines in early 1944 were not combat-ready due to problems encountered during test flights. To bring these aircraft up to combat standards, an intensive modification programme was launched at Salina, Pratt, Great Bend, and Walker air bases in Kansas.

This process, which went down in history as the ‘Kansas Battle,’ was a superhuman effort. Civilian technicians and soldiers from the factories worked day and night on the aircraft, often outdoors in freezing winter conditions because the hangars were inadequate. In an incident that exemplified both the desperation and ingenuity of this effort, Kermit Thompson, the Service Manager in Wichita, removed an urgently needed cable assembly from an aircraft on the Wichita production line on Easter Sunday, concealed the part under his coat, and slipped past a guard to deliver it to the modification centre. This ‘battle’ was, in fact, a microcosm of the entire B-29 programme: a project where production and deployment constantly outpaced development, forcing the immediate implementation of battle-ready solutions under immense pressure. By 15 April 1944, this incredible effort had resulted in 150 combat-ready B-29s being delivered to the XXth Bombardment Command for deployment to the Pacific.

Despite all the difficulties and tragedies during development and production, the urgency of the war ensured the programme gained unstoppable momentum, and the B-29, with all its flaws, began its march towards its ultimate and decisive role in the Pacific.

Section III: War in the Pacific Skies: Operational History

The operational history of the B-29 Superfortress is a vivid example of how strategic bombing doctrine evolved in the face of the brutal realities of war. The aircraft's use in the Pacific underwent a dramatic and controversial shift from the initial dreams of high-altitude precision bombing to ruthless firebombing raids that swiftly destroyed cities. This evolution was the result of both the aircraft's technical limitations and the determination of a military leadership prepared to pay any price to achieve victory.

3.1. Operation Matterhorn: A Risky Gamble Over China

The B-29's first entry into the war was with Operation Matterhorn, an extremely ambitious and logistically nightmarish plan to strike Japan from over China.

Strategic Concept:

In early 1944, the only places within the B-29's range that could strike the Japanese mainland were bases in the interior of China. The plan was to deploy the aircraft at main bases in India and move them to forward bases in the Chengtu region of China to attack targets in Japan.

Logistical Nightmare:

The weakest link in the plan was logistics. With no land connection to China due to the Japanese occupation, all the fuel, bombs and ammunition needed for the forward bases had to be transported from India over the Himalayas, through the dangerous air corridor known as the ‘Hump’. This task was so difficult that it was calculated that ‘for every Superfortress combat mission, the command flew an average of six B-29 round-trip cargo missions over the Hump.’ Aircraft were repeatedly used as cargo planes to carry the fuel needed for their own combat missions.

Operational Results:

The first raids carried out under these conditions were largely ineffective. Attacks on Bangkok on 5 June 1944 and on the Yawata steelworks in Japan on 15 June caused very little damage to their targets due to chronic engine failures, poor weather conditions and scattered bombing.

High operational losses and unsustainable logistical costs revealed the Matterhorn Operation to be a strategic failure.

3.2. The Marianas Campaign: A Shift in Strategy

The shift in the centre of gravity of the Pacific war to the Marianas Islands (Saipan, Tinian, Guam), captured by US forces in the summer of 1944, marked a turning point for B-29 operations.

These islands were much closer to Japan than China and, most importantly, could be resupplied directly by sea. This ended the logistical nightmare of the ‘Hump’.

Hansell's High-Altitude Strategy:

General Haywood Hansell was placed in command of the XXI Bombardment Command established in the Marianas. Hansell, adhering to the US pre-war strategic bombing doctrine, aimed to destroy the Japanese aircraft industry with precision strikes from high altitude (approximately 30,000 feet) during the day. However, this strategy encountered an unexpected enemy: the jet stream. These violent winds, exceeding 200 miles per hour over Japan, scattered bomber formations, disrupted Norden bomb sight calculations, and caused bombs to miss their targets by hundreds of metres. Combined with constant engine problems and poor weather conditions, this factor doomed Hansell's strategy.

LeMay's Radical Change:

In January 1945, General Arnold, having lost patience, removed Hansell from his post and replaced him with General Curtis LeMay, known as a ‘tough, Patton-style commander’ who had gained experience in China. LeMay quickly concluded that high-altitude precision bombing was ineffective and implemented one of the most radical tactical changes in aviation history. LeMay ordered the B-29s stripped of most of their defensive armament and ammunition to carry more incendiary bombs. He lowered the flight altitude to 5,000-6,000 feet and decided to conduct attacks at night with individual aircraft rather than in formation. This tactic eliminated the threat of jet streams and fighter aircraft, increased aircraft performance, and aimed to maximise the damage caused by incendiary bombs in Japan's predominantly wooden cities.

3.3. Firestorms: The Destruction of Japanese Cities

LeMay's new strategy produced horrific results. It is argued that this tactic was not only indiscriminate terror bombing, but also a calculated attack on Japan's decentralised industrial base, woven into the fabric of its wooden cities. Japan's war industry relied on ‘hundreds of small businesses, or “home industries”, widely scattered throughout these combustible areas’. The first major application of this tactic was the raid on Tokyo on the night of 9-10 March 1945. That night, 279 of the approximately 325 B-29s that reached their target struck their targets with M69 napalm bombs from low altitude. The more than 1,650 tonnes of incendiary bombs dropped started a massive fire that spread rapidly through the city's wooden structures and, combined with the wind, created a firestorm. Within just a few hours, an area of 16 square miles of the city was completely reduced to ashes, and an estimated 84,000 people lost their lives. This was one of the largest loss of life in a single air raid. Other major cities such as Nagoya, Osaka, and Kobe followed Tokyo.

The B-29's operations over the marinas had finally transformed the aircraft into an effective and decisive strategic weapon. However, this success was achieved by adopting one of the war's most controversial and destructive tactics: area bombing, targeting civilian centres.

Part IV: Launching the Atomic Age: Operation Centerboard

No moment in the history of the B-29 Superfortress was as decisive as its role in carrying the atomic bombs that ushered in a new and terrifying era in human history. This mission represented the pinnacle of the aircraft's technological capabilities while also cementing its place in history as the carrier of a weapon that forever altered the geopolitical balance. This historic responsibility required both a specially trained unit and aircraft modified to carry this unique payload.

4.1. The 509th Composite Group and the ‘Silverplate’ Project

To carry out the atomic bomb mission, a completely self-sufficient, special unit called the 509th Composite Group was formed under the command of Colonel Paul W. Tibbets. This unit was trained in absolute secrecy at Wendover Airfield in Utah.

Their mission was so secret that even the unit's pilots and crew did not know the true nature of their payload until the very last moment.

For this special mission, the B-29s underwent extensive modifications as part of a project codenamed ‘Silverplate’. The primary aim of these modifications was to create a lighter, faster aircraft capable of reaching higher altitudes, enabling it to carry the ‘Little Boy’ and ‘Fat Man’ bombs, which weighed approximately 10,000 pounds (4.5 tonnes). The main changes made in this context were as follows:

a) All defensive turrets and armour plating were removed, saving approximately 7,000 pounds in weight.

b) The two bomb bays were combined to create a single, large bay capable of holding the massive atomic bombs.

c) More reliable and higher-performance fuel-injected engines and reversible-pitch propellers were installed.

d) A special single-point bomb release mechanism, adapted from the British ‘Type F’ model, was mounted to release the bomb.

4.2. Hiroshima and Nagasaki: Mission Details and Effects

The atomic bomb attacks, codenamed ‘Operation Centerboard’, put the B-29 and its crew's capabilities to the ultimate test.

Hiroshima Mission (6 August 1945):

The B-29 named Enola Gay, commanded by Colonel Paul Tibbets, took off from Tinian Island in the Pacific.

Due to the sensitivity of the mission, the final assembly of the uranium bomb, codenamed ‘Little Boy,’ was carried out in flight by Lieutenant William ‘Deak’ Parsons inside the bomb bay. This was a precaution to prevent a potential accident during take-off from causing a nuclear disaster. At 8:15 a.m. local time, the Enola Gay was over Hiroshima. The target was the Aioi Bridge in the city centre. After the bomb was dropped, Tibbets performed a sharp 155-degree dive-and-turn manoeuvre, which he had rehearsed many times beforehand, to steer the plane away from the shock wave of the explosion.

Colonel Paul Tibbets described the moment after the atomic bomb was dropped and the effects of the explosion as follows:

When the bomb was released, the aircraft instantly became 9,000 pounds lighter. As a result, the aircraft's nose shot sharply upwards, and Colonel Tibbets had to move quickly to accomplish the most important task of the flight: to get his aircraft as far away from the blast point as possible. ‘The 155-degree dive turn to the right at a 60-degree bank angle subjected the aircraft and its occupants to immense pressure.’

Bob Caron, the tail gunner, described this sharp turn as being like ‘being the last man in a game of whipsaw.’

By the time they completed the turn, they had lost 1,700 feet of altitude and were moving away from the target with the engines running at full power.

Midway through the banked turn, he stated that it was necessary to pull back on the control columns (in terms other pilots would understand) to prevent the risk of rolling, and said, ‘I was flying this largest bomber like a fighter plane.’

The 43 seconds between the bomb being released and the explosion passed quickly for Tibbets; he was so focused on flying the plane that he said, ‘even though it lit up the interior for a long moment, the flash did not create the effect one might expect in my mind.’

However, he described experiencing a non-visual, yet very striking sensation:

‘My teeth, more distinctly than my eyes, told me of the Hiroshima explosion.’

At the moment of the explosion, he noted a ‘tingling sensation’ in his mouth and a ‘very distinct taste of lead on his tongue.’ He relayed that scientists later explained this was due to electrolysis, an interaction between the fillings in his teeth and the radioactive forces released by the bomb.

He estimated that they were travelling rapidly eastward while awaiting the shock wave and that when the shock wave reached them, they must have been ‘about nine miles away’ from the point of detonation.

He described the moment the shock wave hit the aircraft as follows:

The shock wave struck the aircraft with ‘violent force’ before Caron could warn them. ‘Our B-29 shook from the impact’ and he stated that he held on tightly to the controls to maintain level flight. Based on his experience flying over targets in Europe and Africa under enemy anti-aircraft fire, he stated that this effect ‘closely resembled the effect of an anti-aircraft shell exploding near the aircraft.’

Once he realised they were safe, he began circling to see the results and observed the enormous purple mushroom cloud described by the tail gunner rising to 45,000 feet. He described this sight as ‘a terrifying image’ and found the view below ‘even more horrific’; the city had become a ‘hideous stain’ and was completely obscured by a terrifying blanket of smoke and fire.

Nagasaki Mission (9 August 1945):

Three days later, the B-29 Bockscar, commanded by Major Charles Sweeney, took off carrying the plutonium bomb named ‘Fat Man’. The mission nearly ended in failure as the primary target, the city of Kokura, was shrouded in thick smoke. With fuel levels critically low, Sweeney was forced to head for the secondary target, Nagasaki. Despite poor weather conditions, a momentary break in the clouds allowed the bomb to be dropped.

Outcome and Strategic Impact:

These two attacks broke the resistance of the Japanese military leadership and led to Emperor Hirohito's announcement of surrender on 15 August. After the war ended, the B-29s took on a ‘mercy mission.’ They saved the lives of thousands of Allied soldiers by parachuting food, medicine, and clothing into prisoner-of-war camps in Japan, China, and Korea.

The B-29 Superfortress, along with its missions to Hiroshima and Nagasaki, has made its mark in history not only as a successful warplane but also as the carrier of a weapon that forever changed the nature of warfare and geopolitical balances.

Chapter V: Post-War Service and Legacy

The legacy of the B-29 Superfortress did not end with the conclusion of World War II. On the contrary, at the dawn of the Cold War, it formed the basis of strategic air power for both the United States and, surprisingly, the Soviet Union. As the last great and effective representative of piston-engine strategic bombers, the B-29 and its derivatives continued to play significant roles at the dawn of the jet age.

5.1. The Korean War: A Piston-Engined Bomber in the Jet Age

When the Korean War broke out in June 1950, the B-29s were once again called to the front line. However, this time the technology and threats they faced were very different.

Initial Tactical Role:

At the start of the war, there were very few strategic targets to strike in North Korea. Consequently, the B-29s were heavily utilised in tactical roles beyond their primary mission, such as providing close air support to ground troops against advancing North Korean forces and interdicting supply lines.

The MiG-15 Threat:

With China's entry into the war, the mastery of the skies changed. The emergence of Soviet-made MiG-15 jet fighters marked a turning point for the piston-engine B-29s. These fast and powerful fighters, with their swept-back wings, made daytime B-29 raids extremely dangerous. Heavy losses were suffered, particularly in the area known as the ‘MiG Corridor’. For example, on 12 April 1951, three out of a formation of 48 B-29s targeting a bridge over the Yalu River were shot down, and many more were severely damaged.

Transition to Night Raids:

Faced with increasing losses, B-29 operations were shifted from daytime to nighttime. Success in these missions was made possible by the use of the SHORAN (Short Range) radar-assisted navigation and bombing system, which could locate targets with high precision. B-29s continued to strike targets in North Korea at night for the remainder of the war.

Result:

By the end of the Korean War, B-29s had flown over 21,000 sorties and dropped 167,000 tonnes of bombs. However, the war painfully demonstrated that this large aircraft was now obsolete in the face of jet fighter aircraft and radar-controlled air defence systems, and that it had to relinquish its strategic bombing role to the new generation of jet aircraft.

5.2. A Copy of the Cold War: Tupolev Tu-4 ‘Bull’

One of the most intriguing espionage and engineering stories of the Cold War is how the Soviet Union acquired its own strategic bomber. During World War II, four damaged or out-of-fuel B-29s (including the Ramp Tramp, Gen. H. H. Arnold Special, and Ding Hao) were forced to make emergency landings on Soviet territory. The Soviets, who were not at war with Japan at the time, seized the aircraft and their crews in accordance with international law. After the war, while the crews were repatriated, the aircraft were not returned. Stalin ordered the Tupolev design bureau to make exact copies of these aircraft. Soviet engineers dismantled the aircraft down to the last screw, measuring, analysing and reproducing every single part. This marvel of ‘reverse engineering’ was named the Tupolev Tu-4 (NATO code name: ‘Bull’). The Tu-4 gave the Soviet Union its first reliable nuclear strike capability and significantly affected the balance of power in the early years of the Cold War by posing a new and serious strategic threat to the United States.

5.3. Service in the Royal Air Force: Boeing Washington

In the post-war period, the United States leased 87 B-29 and B-29A aircraft to the Royal Air Force (RAF) under the Military Aid Programme. Known as the ‘Boeing Washington’ in RAF service, these aircraft provided a crucial ‘interim’ nuclear deterrent capability until the UK's own jet-powered V-bombers (Valiant, Victor, Vulcan) entered service. In addition to their bombing missions, some Washingtons were also used in special roles such as electronic intelligence (ELINT), gathering valuable information across Soviet airspace.

The B-29's diverse roles in the post-war period demonstrated the robustness and adaptability of its design. However, with the irresistible rise of jet technology, which heralded the end of the piston engine era, its replacement by a new generation of aircraft was inevitable.

Section VI: The Evolution of the B-29 Platform: Derivatives and Special Projects

The B-29 Superfortress design served as a versatile platform for a series of innovative and critical roles in post-war aviation, going beyond its initial purpose as a bomber. The robustness and adaptability of its basic fuselage and wing structure enabled it to evolve into a wide range of roles, including tanker, reconnaissance, cargo, and even experimental aircraft carrier. These derivatives demonstrated the forward-thinking nature of the B-29's basic design while directly influencing the future development of strategic aviation.

6.1. B-50 Superfortress: The Enhanced Successor

The B-50 was a direct continuation and improved version of the B-29. Although outwardly very similar to the B-29, it incorporated significant structural and engine improvements.

Key Difference:

The most significant change was the replacement of the problematic Wright R-3350 engines with the much more powerful and reliable 3,500 horsepower Pratt & Whitney R-4360 ‘Wasp Major’ radial engines.

Structural Improvements:

The wing structure, manufactured using a new and stronger aluminium alloy, was 16% stronger than the B-29's wing and 600 pounds lighter. Additionally, a larger vertical stabiliser (tail) was added to cope with the increased engine power.

Role:

The B-50 formed the backbone of the Strategic Air Command's (SAC) nuclear deterrent until the first generation of jet bombers, such as the Convair B-36 and Boeing B-47 Stratojet, entered service.

6.2. Flying Petrol Stations: The KB-29 and KB-50 Tankers

The B-29 and B-50 platforms played a pioneering role in the development of modern air-to-air refuelling technology. This capability dramatically increased SAC's global range and strategic flexibility.

KB-29M (Hose System):

Initial trials were conducted using a hose system developed by the British company Flight Refuelling Ltd. Described in source texts as ‘cumbersome and impractical,’ this system involved connecting the tanker and receiver aircraft with cables, through which the fuel hose was then transferred. This system was particularly challenging in adverse weather conditions.

KB-29P (Flying Boom System):

A much more efficient and safer system was the ‘Flying Boom’ developed by Boeing. This system used a telescopic boom with small wings, guided by an operator in the tanker's tail. This system formed the basis for today's air-to-air refuelling operations and is still in standard use.

KB-50J/K:

Tankers converted from the B-50 platform were developed to refuel jet fighters and bomber aircraft at higher speeds and altitudes. The performance of the KB-50J/K models was significantly enhanced by adding a General Electric J47 jet engine under each wing.

6.3. Experimental Aircraft and Special Missions

The versatility of the B-29 platform made it the carrier for some of the most unusual and innovative aviation projects of the 20th century.

X-1 and D-558-II Carrier Aircraft:

Experimental rocket-powered aircraft such as the Bell X-1, which achieved the first manned supersonic flight, carried too little fuel to take off from the ground on their own. Therefore, the B-29 or its Navy version, the P2B-1S (the aircraft used in the D-558-II mission and nicknamed Fertile Myrtle), carried these rocket planes to high altitude using a special rig mounted in the bomb bay and released them in flight.

XF-85 Goblin Parasite Hunter:

In the early days of the Cold War, the idea of bomber aircraft carrying their own fighter escorts was tested. The XF-85 Goblin, a miniature jet fighter developed for this purpose, was carried on a trapeze lowered from the bomb bay of an EB-29. The project was cancelled because it was extremely difficult for the aircraft to return to the mother ship.

Project Tip Tow:

Another radical concept tried to increase the range of fighter aircraft was to attach them directly to the wingtips of a B-29. This would allow the fighter aircraft to cover long distances without using their own engines. However, the project was terminated after a disastrous accident during trials, in which an F-84 lost control and crashed into the B-29, resulting in the loss of both aircraft.

Stratovision:

In this project, which could be considered a pioneer of satellite broadcasting, a B-29 aircraft was used as a flying TV transmitter to broadcast television signals over a wide area from high altitude. A massive antenna mounted under the aircraft ensured that the signals could reach hundreds of miles away.

The B-29 platform's adaptability to such a wide variety of roles proves that it was not only a successful bomber aircraft but also left a fundamental engineering legacy in 20th-century aviation history and inspired many aircraft that came after it.

A total of 3,970 Boeing B-29 Superfortress aircraft were built. Within this total, the main production versions and their production numbers are as follows:

a) B-29 (Basic Model):

A total of 2,513 were produced in this version. This production was spread across different manufacturers:

-1,620 by Boeing (Kansas, Wichita) (B-29-BW).

-Martin (Nebraska, Omaha) produced 536 (B-29-BA).

-Bell Aircraft (Georgia, Marietta) produced 357 (B-29-BO).

b) B-29A Model:

This version was produced by Boeing at its Renton facility between January 1944 and May 1946. A total of 1,119 B-29As were built.

c) B-29B Model:

This lighter version was produced only by Bell-Atlanta, with a total of 311 built between January and September 1945.

Following the end of World War II, the 5,092 orders placed for the B-29 were cancelled; however, the limited number of aircraft remaining on the production line were allowed to be completed. The last B-29 was delivered on 10 June 1946, bringing the total number built to 3,627 B-29s.

Conclusion: The B-29's Lasting Impact

The Boeing B-29 Superfortress left an indelible and multi-layered mark on aviation and military history. It was not merely a machine of metal, propellers, and engines, but also a symbol of technological revolution, a will that pushed the boundaries of industrial production on a global scale, and a turning point that fundamentally changed the nature of warfare. With its pressurised cabin, remote-controlled defence system, and advanced aerodynamic design, it was an engineering marvel far ahead of its time. Its production programme mobilised America's industrial might on an unprecedented scale. Its operational history, from initial failed high-altitude precision bombing attempts to the ruthless firestorms that reduced cities to ashes, reshaped the doctrine of strategic bombing.

Ultimately, by carrying its payload to Hiroshima and Nagasaki and ushering in the atomic age, the B-29 forever changed not only how war was fought, but also how it was conceived. Its legacy did not end with the conclusion of World War II. It made its final stand against the jet age in the Korean War, became a replicated model of the Soviet Union's first strategic deterrent, and continued to influence the development of modern aviation for decades through a lineage that included the B-50 bomber, the KB-29 and KB-50 tankers, and countless experimental platforms. The B-29 Superfortress has secured its place in history as an unforgettable monument to both creative genius and destructive power.

References

https://6thbombgroup.com/the-b-29-bomber/

https://warfarehistorynetwork.com/building-the-b-29/

https://en.wikipedia.org/wiki/Boeing_B-29_Superfortress

Simons, Graham M. B-29 Superfortress Giant Bomber of World War Two and Korea. Barnsley, South Yorkshire: Pen & Sword Aviation, 2012