B-29: Superfortress

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THE BOEING B-29 SUPERFORTRESS The giant bomber of World War Two and Korea.’

By Graham M Simons

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CONTENTS

Introduction

5

Origins

7

Birth Pains

25

Early Aircraft

49

China

61

Into the Pacific!

91

Operation Centreboard

109

Peace - and a ‘Police Action’

145

Washingtons and Tankers

165

The B-50

179

The Tu-4 ‘Bull’

197

Specials

207

Operating the B-29

229

Bibliography

250

Index

251

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ACKNOWLEDGEMENTS A project of this nature could not be undertaken without considerable help from many

organizations and individuals.

Special thanks must go to Marilyn Phipps of Boeing Archives, Col. Richard L Upstromm and Tom Brewer from the USAF Museum, now the National Museum of the USAF for the provision of many photographs and details.

Background to the development and procurement of all the B-29 projects, can be found in published and unpublished primary source research material in the form of memoranda, policy statements and other documents from the Army Air Corps, the Navy, and Carl L. Norden inc., provided to us by Lynn Gamma and all in the U.S. Air Force Historical Research Center at Maxwell Air Force Base, Montgomery, Ala. The same applies the valuable services provided by the History Office of the Air Technical Service Command, Wright Field, Dayton, Ohio. Much other primary source documentation is also located in the National Archives and Records Administration at College Park, Maryland.

The archives of the National Advisory Committee for Aeronautics provided access to all their relevant material, as did the archivesof the Institute of Aircraft Production provided much information and a number of photographs, as did the RAF Museum, the Imperial War Museum and the Science Museum in London.

The late Roger Freeman provided photographs, as did Simon Peters and Martin Bowman and Peter Green from their respective collections.

Personal thanks must also go to David Lee, the former Deputy Director and Curator of Aircraft of the Imperial War Museum at Duxford, John Hamlin and to Vince Hemmings, the former curator of the East Anglian Aviation Society’s Tower Museum at Bassingbourn.

The author is indebted to many people and organisations for providing photographs for this book, many of which are in the public domain. In some cases it has not been possible to identify the original photographer and so credits are given in the appropriate places to the immediate supplier. If any of the pictures have not been correctly credited, the author apologises.

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INTRODUCTION The Boeing B-29 Superfortress, along with the fallback design of the Consolidated B-32 Dominator should the Superfortress prove unsuccessful, were two very heavy bomber designs that originated in the latter part of the 1930s which were intended to replace earlier, smaller four engined designs.

The B-29 was the progenitor of a series of Boeing-built bombers, reconnaissance aircraft, trainers and tankers and airliners including the B-50 Superfortress, the C-97 Stratofreighter the Model 377 Stratocruiser. Later jetpowered models from Boeing carried on the lineage.

The B-29 was one of the largest aircraft to see service during World War Two. It was a very advanced bomber for this time period that included features such as a pressurized cabin, an electronic fire-control system, and remote-controlled gun turrets. Though it was designed as a high-altitude daytime bomber, in practice it actually flew more low-altitude nighttime incendiary bombing missions. It was the primary aircraft in the American fire-bombing campaign against the Empire of Japan in the final months of World War Two, and carried the two atomic bombs that destroyed Hiroshima and Nagasaki. Unlike many other bombers from this The classic image of the era, the B-29 remained in service long after the war ended, with a few even being B-29 - high over Mount employed as flying television transmitters for the Stratovision company. The type Fiji in Japan. (USAAF)

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In close at the moment of was finally retired in the early 1960s, with 3,970 aircraft in all built.

There were many early problems - The most common cause of maintenance weapon release. A pair of release headaches and catastrophic failures was the engine. Although the Wright R-3350 19th BG B-29s their bombs. later became a trustworthy powerplant of large piston-engined aircraft, early (USAAF) models were beset with dangerous reliability problems. This problem was not fully cured until the aircraft was fitted with the more powerful Pratt & Whitney R-4360 ‘Wasp Major’ in the B-29D/B-50 programme, which arrived too late for World War Two. Interim measures included cuffs placed on propeller blades to divert a greater flow of cooling air into the intakes, which had baffles installed to direct a stream of air onto the exhaust valves. Oil flow to the valves was also increased, asbestos baffles installed around rubber push rod fittings to prevent oil loss, and thorough pre-flight inspections made to detect unseated valves. This was as well as frequent replacement of the uppermost five cylinders for every 25 hours of engine time and the changing of entire engines every 75 hours!

This then is the story - of trials and tribulations to eventual success!

Graham M Simons Peterborough December 2011

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ORIGINS German troops had already marched into Vienna and Hitler proclaimed chief of the state when in March 1938 the US Army Air Staff, seeking an economical method for equipping the Air Corps, asked Boeing to submit ideas for pressurizing the cabin of the B-17 Flying Fortress.

Appropriations for purchase of military aircraft were extremely modest; all decisions were influenced by a need for economy. In 1938 only $62,602,727 had been appropriated for the overall support of Army aviation—aircraft, maintenance, operating cost and officer and personnel training—a sum less than the cost of one capital ship!

Six desirables were evident in aircraft design trends of the times. Boeing's spectacular pressurized-cabin Stratoliner had proved the wisdom of the first desirable. The bomber of the future must possess a pressurized cabin to provide improved comforts for the crew and permit the craft to fly above storms and flak.

Secondly, it must have tricycle landing gear, to make for ease of handling on the ground and to improve landings – for many years this remained a moot point, for tricycle landing gear ‘cost’ the B-29 nearly two thousand pounds of extra weight.

Thirdly, it must have greater speed; fourth, greater range; fifth, greater bomb New York gets a view of capacity; and sixth, greater interchangeability between fuel and bombs. This the YB-17, one of the meant larger fuselages. pre-production Company design engineers set to work; their job was to conceive and prepare machines, when the drawings of new aircraft believed to be of interest to the Air Corps and to prepare 96th Bombardment Squadron took its major revisions to existing designs. Their first task was to determine whether they aircraft over the city at had exploited to the fullest all the virtues of two existing designs: they studied the low-level. company's XB-15, then the world's largest land aircraft, of which only one had (USAAF)

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been built and they studied, in parallel, the B-17 design. Could they ‘squeeze’ these aircraft into pressurized cabin models with tricycle landing gear, making them speedier, more far-ranging; could they make them carry more bombs?

From parallel studies made during the first half of 1938, two preliminary sketches emerged: Model 316, a modernized version of the XB-15, and Model 322, an improved version of the B-17 Flying Fortress. The ancestry of both Models 316 and 322 was above reproach. The XB-15 was to win world records for load-carrying to specified altitude. The B-17, then undergoing gruelling accelerated service tests, of which goodwill flights to Latin America were the most dramatic, and which had also broken world records for speed and altitude, was establishing the basic philosophy for the Air Corps heavy bombardment programme to come.

Model 316, A, B, C and D versions, offered variations of high and low-wing monoplanes. Model 322 was a mid-wing monoplane. Both the Model 316 series and Model 322 had pressurized cabins and tricycle landing gear. Both had good range, but they were not by any means the ‘fastest and the mostest’ aircraft Boeing designers believed were in the Air Corps' vision. And so, because improvements suggested in these designs were not convincingly beyond Flying Fortress performance of that day, and

The Boeing XB-15 in flight, low over the Wright Brothers Kittyhawk memorial.

(Simon Peters Collection)

Boeing only built ten Model 307 Stratoliners, but discovered one modification that was needed which changed the appearance of all subsequent B-17s - the extended fin that was to generate the nickname ‘big-assed bird’. The change is evident in this photograph of a TWA 307 Stratoliner.

(Real Aircraft Photographs)

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ORIGINS

Boeing executive Phillip Gustav Johnson (b. 5 November 1894, d, 13 September 1944)

9 because these marginal improvements promised would not be commensurate with cost, Boeing 316 and 322 designs never officially reached the Army.

A number of people and organisations played important rolĂŠs in the B-29 story. Philip G Johnson had returned to Boeing as president in September 1939. To Johnson fell the major task of contract negotiation with the Army for the aircraft to be known as B-29. This work was a role with which Johnson was familiar, for he was a man who had been reared in the Boeing organization. Upon graduation from the University of Washington in the spring of 1917, Johnson became draftsman for the Boeing company; five years later he had risen to vice president, general manager; in 1926 he was made president and general manager. In three years he was head of the sprawling Boeing aircraft and transport interests. He was president of United Aircraft and Transport Corporation, makers of the Pratt & Whitney engines, and president of United Air Lines.

Resigning in July 1934, following the inquisitions of the Black Air Mail Committee at the time of the cancellation of the air mail, Johnson had entered the truckmanufacturing business. For a few years he took life easy. Then, in 1937, at invitation of the Canadian Government, he had established the operations of Trans-Canada Air Lines.

With him Johnson brought as executive vice president a man completely familiar with the requirements of aircraft production: H Oliver West. Boeing had also been West's Alma Mater. Joining the Boeing family in 1921 as an inspector of raw materials, he rose quickly to production chief; became superintendent of Boeing Air Transport's maintenance; retained the same job with United Air Lines and followed Johnson to Trans-Canada.

West's first act was to develop the plan for a new modern factory, to displace the old Plant One, by a sweeping expansion of the new Plant Two, a small portion of which had already been built. They must buy machine tools, millions of dollars worth, and get set to turn out Flying Fortresses in an efficient operation.

Later dubbed Multi-line Production, the West system called for the precompletion of Fortresses in major sections or components and production lines which converged just before the factory door. These major sections were then hooked up, joined, and the aircraft was rolled out of the door. It was similar to what Consolidated and Fords were doing with the B-24.

On 17 June 1940 the Army had expressed its interest in substantiating wind tunnel data and with a mock-up of the XB-29, three major forces went into action: preliminary design engineers working closely with aerodynamicists, and with project engineers, advancing the design forwards.

The designers fell into two categories: research engineers and project engineers. Over a period of two years, preliminary design engineers and aerodynamicists had developed their design thinking to the promise stage. The heart of the bomber was the bomb bay, obviously built around the nature of the bombs, their sizes and number, the limiting fall angles and the hoisting clearances necessary for the bombs.

This determined the size of the fuselage. From there they drew the body design, the wing, the landing gear, the equipment and interior arrangement of the aircraft,

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its controls and control surfaces and its armament.

Remembering that the USAAF was the only customer for the embryonic Superfortress - it is not surprising that Wright Field and the Air Technical Service Command was constantly and closely involved with the B-29.

The War brought the AAF Materiel Command and Air Service Command - which merged in 1944 into the Air Technical Service Command (ATSC) with headquarters at Wright Field, Dayton, Ohio into greater prominence than ever before. The Command's mission was three-fold: to conceive aircraft designs and put them through experimental development; purchase them in quantities and place them into production in minimum time.

The Air Technical Service Command was the branch of the Army Wellwood E Beall, Air Forces responsible for the engineering, procurement, production, Boeing’s Chief supply and maintenance of all Army aircraft. To fulfill this responsibility ATSC Engineer.(b.

1907, d. had six divisions: Engineering, Procurement, Supply, Maintenance, Personnel and 1978) Base Services. It was the job of the Engineering Division to keep three years ahead of the then contemporary aviation by thinking in terms of the future. The B-29 was perhaps the most conspicuously successful example of the Army Air Forces' capacity for achieving long-range planning.

Throughout the conception, design, construction, flight test, programmemanufacturing and combat phases of the Superfortress story the Air Technical Service Command provided significant skills and thinking, vital to the successful completion and use of the B-29.

There were four very important players in the genisis of the B-29. 33 year-old Chief Engineer Wellwood E Beall was a product of University of Colorado and New York University. He had joined Boeing as instructor of drafting, mathematics, aerodynamics, structures, aircraft history and Air Commerce Regulations at the Boeing School of Aeronautics, Oakland, California; he later became Boeing's Far Eastern manager, selling pursuit planes to the Chinese Air Force. Returning in 1935, Beall was transferred to the engineering division, and as chief commercial project engineer played a major part in the design of the Clipper.

Edmund T Allen, 43, Chief of Boeing Flight Test and Aerodynamics staff, was at the time acclaimed as the world's greatest test pilot. Eddie Allen's life had been consecrated to the quest of aircraft stability and control. By 1940 his patience Edmund T. ‘Eddie’ Allen and pure scientific approach toward the flight-testing of aircraft had established (b.4 January 1896, d. 18 February 1943). him as the pre-eminent authority in the refinement of stability and control of heavy aircraft. His proved procedures for cruising operations of air transport craft had become the bible for practically all air transport operators in the world and his work with the Stratoliner and the B-17C and D Flying Fortress series had conquered for man’s flight purposes, the thin, blue regions of the Stratosphere.

Working with Eddie Allen, as chief aerodynamicist, was George S Schairer, 27, graduate of Swarthmore and the Massachusetts Institute of Technology.

Edward Curtiss Wells, 29, a quiet genius with a lusty sense of humour so skillfully concealed it had a way of surprising even his closest friends. At twenty-three, this graduate of Stanford University had already

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ORIGINS

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The Model 316 of March, 1938.

Type: High-wing, pressurized cabin monoplane with tricycle landing gear, the main gear having double wheels.

Size: Wing span, 157 feet; length, 109 feet, two inches.

Design Gross Weight: 89,900 pounds.

Maximum Alternate Gross Weight: 89,900 pounds Power Plant: Four Wright R-3350 developing 2,000 HP for take-off.

Wing Loading: 31 pounds per square foot.

Range with 2,000 lb of bombs: 4,000 miles.

Speed: 248 mph at 15,000 feet.

Armament: Seven .50 machine guns.

Maximum bomb load: 19,400 pounds. Crew: Nine

designed major portions of the Flying Fortress. As assistant chief engineer and spark plug of detailed design, Wells was to give expression to even greater talents in design of the B-29.

Overcoming the challenges The overall design and evaluational problem facing Boeing at that time was: how to give an aircraft possessing twice the weight of the Flying Fortress thirty percent more speed with only eighty- three percent more horsepower? The magnitude of their problem could be stated in the cube-square law - to double the speed there had to be eight times as much power; for in doubling the speed ordinarily this produced four times the drag. Inasmuch as the power was fixed by the engines available, designers were relying on a big ‘assist’ from the aerodynamic cleanness they were giving the XB-29.

Aerodynamicists and powerplant engineers wrestled with the problem of propellers, their ideas moving toward the adoption of an entirely new propeller gear ratio for the Superfortress. For years scientists had known propeller tip speed must be kept as low as possible; where speeds approached the speed of sound a phenomena known as compressibility burble - a sudden high-drag action -

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BOEING B-29 SUPERFORTRESS The Model 322 from June, 1938.

Type: Mid-wing, pressurized cabin monoplane with singlewheeled tricycle landing gear.

Size: Wing span, 108 feet, seven inches; length, 75 feet, five inches Design gross Weight: 40,000 pounds Maximum Gross Weight: 53,100 pounds Powerplant: Four Pratt and Whitney R-2180 developing 1,400 HP for take-off Wing Loading: 35 pounds per square foot Range with 2,000 pounds of bombs : 3,600 miles Speed: 307 mph at 25,000 feet.

Armament: Four .50 machine guns Maximum Bomb Load: 9,928 pounds.

Crew: Six

appeared. Compressibility burble is almost like a rock wall. Thus, it was known that the propellers must turn ‘slowly.’

At the time propellers of most aircraft turned at 44% of engine speed. Engineers believed this would be too ‘fast’ for the B-29; this propeller speed would reduce high altitude performance of the aircraft. Furthermore, at this prop speed, sixteen mph would have to be be sacrificed. Wright Aeronautical engineers were asked for a propeller ratio enabling the B-29's propellers to turn more slowly. As a result Wright engineers proposed, and eventually achieved, a gear ratio which would turn the propeller at 35% of engine speed, making the B-29's propellers the slowest turning on any aircraft. After sweating out extensive propeller tests, the Hamilton Standard three-bladed propeller was initially adopted. Later another blade was added.

More and more tunnel models were built to sort through all aerodynamic unknowns - Where should the engines be placed? What shape of nacelle would cool the engines best? Model makers built up and scraped down, numerous clay nacelles in the constant hunt for that desirable shape which would accommodate the engines and accessories.

Structures, light of weight and adaptable to quantity production, were built

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The Model 333 of 26 January 1939) Type: High-wing, pressurized cabin monoplane with singlewheeled tricycle landing gear Size: Wing span, 109 feet; length, 80 feet, eight inches Design Gross Weight: 41,000 pounds Maximum Alternate Gross Weight: 48,600 pounds Powerplant: Four Allison 1710 developing 1,150 HP for take-otf Wing Loading: 34 pounds per square foot Range with 2,000 pounds of bombs: 3,420 miles Speed: 307 mph at 15,000 feet Armament: Five .50 machine guns and one .30.

Maximum Bomb Load: 5,800 pounds.

Crew: Six.

and proven. The research had to be right, and tests had to be comprehensive before the first XB-29s were built. If there had been time to place a small quantity of B-29s in the field long before Boeing had started engineering for production and long before the jigs and tools were built for production, then the job could have been done with less risks.

In January, 1939, Boeing engineers swept all existing design adaptation ideas from their heads and turned out Model 333. This design reflected the latest aerodynamic concepts of the times: the thought that the progressive aircraft must be aerodynamically cleaner and possess minimum size if it were to do a maximum job. Remarkably, they were not alone in their thinking – in the United Kingdom Geoffrey de Havilland and his chief designer Ronald Bishop were thinking along similar lines - what evolved from the drawing boards at Hatfield was the incredible De Havilland Mosquito.

These apparently diametrically opposed factors posed a challenging job of design refinement. Model 333 was a distinct break with tradition, an aircraft of substantial aerodynamic cleanness with four engines mounted in tandem arrangement, two Allison liquid-cooled V-type engines placed in tandem, one tractor and one pusher in each nacelle, one nacelle in each wing. Air observers returning from Europe described tail

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BOEING B-29 SUPERFORTRESS The Model 333-A from January 27, 1939.

Type: High-wing, pressurized cabin monoplane with singlewheeled tricycle landing gear Size: Wing span, 108 feet, six inches; length, 80 feet, eight inches Design gross Weight: 40,500 pounds Maximum Gross Weight: 48,600 pounds Powerplant: Four Allison 1710 developing 1,150 HP for take-off Wing Loading: 34 pounds per square foot Range with 2,000 pounds of bombs: 3,000 miles Speed: 328 mph at 15,000 feet Armament: Five .50 machine guns and one .30 Maximum bomb load: 5,800 pounds.

guns as mandatory; and so, for the first time, tail guns appeared in a Boeing design.

For the first time, too, double tandem bomb bays appeared.

But definite built-in disadvantages to the overall design of this machine appeared: rear engines would be difficult to cool; high, and therefore heavy landing gear would be required to ensure landing and take-off ground clearance for the pusher propellers. Because of the distribution of dead weight in the wing, wing tortional and vibration characteristics were involved.

There was also the problem of finding a wing that would promise unparalleled performance. The wing must possess low drag at high speeds; low drags at cruising and a high lift coefficient and good stall characteristics. A search undertaken by Eddie Allen and George Schairer's staff for a high performance wing for the B-29. Every worthy idea was thoroughly explored and evaluated with powered wind tunnel models, a practice which the Company had pioneered in the development of the Stratoliner. For two months they debated with David R Davis, the consulting aerodynamicist whose laminar flow wing that had been used on the Consolidated B-24 Liberator. After fruitless exploration to prove that the Davis wing could provide what was needed, Beall gave the official decision: Boeing aerodynamicists would develop their own wing.

Crew: Six

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The 333-B of 21 February 1939.

Type: High-wing, pressurized cabin monoplane with singlewheeled tricycle landing gear Size: Wing span, 111 feet; length, 80 feet, eight inches Design Gross Weight: 46,000 pounds Maximum Alternate Gross Weight: 52,180 pounds Powerplant: Four Wright 1800 horizontal engines developing 1,850 HP for take-off Wing Loading: 34 pounds per square foot Range with 2,000 pounds of bombs: 2,500 miles Speed: 364 mph at 20,000 feet Armament: Five .50 machine guns and one .30.

Maximum bomb load: 5,800 pounds.

Crew: Six

And so, preliminary design engineers, making haste slowly in January, February and March, 1939, laid out Models 333-A, 333-B and 334, all high-wing pressurized cabin monoplanes with tricycle landing gear and each placing emphasis on submerged engine installations, engines which existed only in the minds of engine designers. At the time both Wright Aeronautical and Pratt & Whitney engine-makers were planning to develop horizontal-type, liquid-cooled engines to make these wing-installations possible. All these models were trying to do the same job: achieve maximum aerodynamic cleanness.

After performing a myriad of calculations during March, April and May, Boeing designers came to the reluctant conclusion that the long propeller shafts required in Models 333-A, 333-B and 334 would introduce disadvantageous features; also that because of the thick, high-drag wing - brought about by the submerged engines many of the aerodynamic gains of the submerged engines were more theoretical than real. Even those gains would be negated by the additional weight occasioned by cutting the wing structure to receive the engines. Added to these disadvantages were increased cooling problems, the major hazard in designing an aircraft completely around new engines of revolutionary and unproved design, and the fact that the range of the designs was crippled: there was too little room in the wings for fuel tanks. And so, in July, after

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BOEING B-29 SUPERFORTRESS The Model 334 on 4 March 1939.

Type: High-wing monoplane with pressurized cabin, singlewheeled tricycle landing gear and twin tail Size: Wing span, 120 feet; length, 83 feet, four inches Design Gross Weight: 49,750 pounds Maximum Alternate Gross Weight: 66.000 pounds Poweplant: Four Pratt and Whitney 1800 Flat engines developing 1,850 HP for take-off Wing Loading: 40 pounds per square foot Range with 2,000 pounds of bombs: 4,500 miles Speed: 390 mph at 20,000 feet Armament: Five .30 machine guns and three .50 Maximum bomb load: 7,830 pounds.

Crew: Nine

much shadow-boxing over their drawing boards, engineers made another clean break with past thinking and designed Model 334A. During all these design experiences, designers had sought to avoid committing themselves to any design which would involve increasing wing loading – that is the weight to be carried by each square foot of wing area. This dread of increasing wing loading, at that time, amounted almost to a phobia in the aircraft industry.

The old adage of ‘High wing loading means dangerously high landing speeds,’ had been around for a long time. But before engineers had completely explored their next design. Model 334-A, they had convinced themselves that wing loading in a practical sense was largely a state of mind, all other things being equal. Their exploration persuaded them that once the highly loaded wing was safely air borne, high wing loading had wonderful virtues in low drag and great range. Their problem was to design a wing flap to assist the take-off and reduce the landing distance.

Conceived in July Model 334-A, the first ‘blood ancestor’ of the B-29 stemmed from this thinking. Of radical departure from previous models, the 334-A should not actually bear a 334 series identification.