The Japanese attack on Pearl Harbor in December 1941 exposed to the world the woeful obsolescence of the Army Air Corps arsenal. It was clearly evident that the aircraft the U.S. had in service on that "day of infamy" would not be sufficient to carry out the global war necessary to defeat the Axis powers. Even as the aircraft industry re-engineered current bomber designs and reorganized itself for mass production, its engineers immediately set upon the task of designing all new aircraft. The current bombers could be improved to fight the holding war, but it might take a "super bomber" to win it. This "superbomber" was to become the B-29 Superfortress.

The genesis of the B-29 can be traced back as far as March of 1938 when Boeing produced a design study, model 334, which was to be "a pressurized version of the B-17 with tricycle undercarriage. " (70) With prewar Air Corps' appropriations as difficult to obtain as they were, Boeing shouldered the financial risk and self-funded the building of a mockup in December 1939. This "model 334A" was the first direct predecessor to the B-29. (71)

Late that same year Air Corps director "Hap" Arnold set out to get official approval to let contracts for a "superbomber," and early in 1940 a message was sent to various aircraft companies spelling out specs for such a bomber (in much the same way as in 1934, when the B-17 was created) this new "very heavy, very long range bomber" was to have a top speed of over 400 miles per hour, a range of 5,333 miles and the ability to carry a one ton payload half that distance. (72) By February, Boeing had submitted their design concept, the model 341. As lessons were learned in the war in Europe, the air corps specs were augmented to include defensive armament, protective armor, and self sealing tanks. Boeing's revised bid, the model 345, was judged the winner and Boeing was appropriated $3.7 million to produce three prototypes of the "X-B29" for testing. (73)

By September of 1941, the B-29 had already begun making history as the U.S. Government placed an order for 250 production bombers as well as 14 more test aircraft "off the drawing board". The Martin B-26 was the only previous bomber ordered before it existed, but the Marauder was a far simpler design than the ambitious B-29 project. Construction of the XB-29, which had to be ready to fly by August of 1942, began six months before all aerodynamic tests were completed, and a full year before drawings of all the parts were available. (74)

On September 21, 1942 the first XB-29 made her maiden flight. (75) In an event eerily similar to the loss of the original B-17, the program endured a tragic setback on February 18, 1943. Test pilot Eddie Allen, his entire crew, and several civilians were killed when an engine fire brought the second prototype down and it slammed into a meat packing plant. Unfortunately, engine overheating and fires would prove to be a chronic problem with the early Superforts.

In April of '43 the first of 14 YB-29s (which featured an engine upgrade and four-bladed propellers) rolled off the Boeing Wichita plant assembly line for testing. In an effort to get the Superfort into the war as quickly as possible, the Air Corps devised an ingenious plan of "parallel testing." While Boeing and Air Corps officials tinkered with minor design details (gun placement, etc.) on each of the YB-29s, flight testing and crew training were done simultaneously, to make certain that as soon as the new bombers were ready, there would be experienced crews to man them. (76) While the "wrinkles "were being ironed out in the test aircraft, production B-29s were already being built in Boeings Wichita, Kansas facility, and the first Superfortress rolled off of the lines in September 1943. It had become increasingly clear that the Superfortress would appear in the war too late to play a major pre-invasion role in Europe. Instead, Boeing employees in Wichita fought the "Battle of Kansas", a mad scramble of design changes and upgrades, to get the B-29 ready to spearhead the strategic air offensive against Japan.

The 20th Air Force, the first to be outfitted with the new Superfortress, was activated on April 4, 1944. Roughly two months later, on June 15th, the 20th saw its first belligerent action against the Japanese homeland. This 68 plane raid on the Imperial Iron and Steel Works at Yawata, although not significant in damage (77), was a harbinger of the relentless Allied Pacific air campaign that was to come. In many ways, the Superforts' bombing of Yawata marked the beginning of the end of the Japanese Empire.

The fact that the B-29 served in the Second World War at all is testament to the sweeping advances in the aircraft industry. The specifications for the B-29 pushed Boeing's engineering team to the limit of the day's technology, and often a little bit beyond. Although Boeing designers had the advantage of the invaluable experience gained from working with the B-17 and B-15, the B-29 was so advanced that it presented problems that engineers had not previously had to contend with. From top to bottom, right down to the simplest parts, the B-29 was totally new; an aircraft designed during WWII for service in WWII.

For example, in general terms, the bulkhead is by far the simplest component of an airplane. Not so with the B-29. The Superfort was to be pressurized, which added a whole new set of problems for Boeing engineers. In fact, about roughly the same number of engineering hours went into designing a B- 29 bulkhead, as engineering a complete fighter plane of 20 years before. (78) And the bulkheads were the least of their problems.

The greatest engineering difficulties arose do to the Army's specified speed and size requirements for the B-29. Every extra mile per hour of speed, every extra 1000 feet of altitude opened a new can of worms and problems, as the Boeing engineers time and time again ran into previously unknown laws of nature, and more specifically, unknown problems of high speed aerodynamics. The development of the B-29 provided fundamental challenges in all aspects of aerodynamic engineering. As a general law, the horsepower requirement goes up as the cube of the desired velocity, to make a B-17 that flew twice as fast, an engine with eight times the horsepower was necessary, and the B-29 was to be almost twice as big as the B-17. Understandably, Boeing engineers made reducing the drag coefficient the first order of business. (79)

To oversimplify the problem, with the limited power that was available, Boeing had to design the B-29 so that it made about the same size hole in the air as the much smaller B-17 if it was going to be able to meet the Air Corps' speed requirements. (80) The first step was the wing design. Boeing decided on their "117" wing design, a hybrid that combined the high speed high altitude characteristics of the B-24's Davis wing with the overall ruggedness of the B-17 wing. (81) Every effort was made to reduce air resistance, necessitating the Superforts' characteristic teardrop windshield. Completely retracting and enclosed landing gear prevented the buffeting caused by leaving the tires exposed to the airstream (as in the B-17). Radio loops and pitot tubes were also kept as streamlined as possible, and all intakes, drains, and vents were built flush with the skin. The skin itself was completely butt-jointed and flush riveted in an effort to reduce drag. Finally, small remote control gun turrets were decided on because they developed less turbulence than turrets large enough to hold a man, and they were easier to pressurize. (82)

Once the aerodynamic cross-section was whittled to an acceptable level, an engine had to be decided upon that could generate the massive power necessary. A the time, the only engine available with the horsepower to do the job was the 18 cylinder Wright R-3350 Cyclone, at the time the most powerful and complicated ever built. Unfortunately, they had never been fully tested and only about 100 of them even existed. (83) The only other plane to use this engine was the mammoth Douglas XB-19 and it had been plagued with a history of cooling problems. Boeing knew that if this engine, which generated its 2200 HP with higher revs and greater compression (84), was to be used, they would have to devise an effective way to keep it cool.

This requirement led to one of the most nagging problems of the early days of the Superfort: the design of the engine nacelles. The nacelles, which already had be large enough to house the retractable landing gear the R-3350's twin superchargers, and other equipment, also had to retain its aerodynamic integrity. The cowlings likewise had to be large enough in frontal area to keep the super-hot engines cool without causing a great deal of aerodynamic drag. Boeing's solution to this problem was to merge all intakes into a single large duct at the bottom-front of the cowling. This intake, though comparatively small was proved to admit more air than any other cowling intake duct in existence. (85) Still, the massive Cyclones could not be kept cool enough, and heat-related failures led to engine fire problems (including the tragic loss of the second XB-29) which caused the most production delay of any single component of the B-29. (86)

Unfortunately the problems with the engines were attributed to an inherent engine design flaw, something Boeing had no control over. In the words of Major V. C. Agather of the Wright field project office:

The source of the original engine fire problem went back to the original design by Wright aeronautical, ... original engines had a high amount of magnesium in the crankcase and accessory housing. ..and would break up when vibrations and moments of inertia were developed, because of the peculiarities of magnesium crystals. ..a complete redesign of the engine was required, but in no measure were we in a position to change basic design, because of the time factor require to accomplish these changes, and still meet production schedules. (87)

In an effort to address the problem, the first YB-29 was sent to General Motors for a trial installation of specially designed liquid-cooled Allison V-3420 engines and further tests. However, the XB-39 Spirit of Lincoln, did not perform sufficiently to justify the design and production switch. Boeing engineers now had only one available course of action. They had to do some creative problem solving and "engineer around" the problems of the engines. They had to get the Superforts flying, and the Cyclone was the only powerplant available with the requisite horsepower.

Through hours and hours of testing and countless minor modifications to carburation, turbosupercharging, the oil circulation systems, and the total redesign of the engine cowl-flaps, the engine difficulties were "minimized" by the time the B-29 was activated for military duty in June 1944. (88)

The Superforts' first mission against "Japanese Pittsburgh" at Yawata marked the successful culmination of the most extensive project in the history of aircraft engineering and manufacture. In the midst of global war, the aircraft industry was able to stretch its collective ideology and knowledge to the limits, and produce in just a few short years, the most advanced bomber, and arguably aircraft, the world had ever seen. The industry had provided the Air Corps with tool it needed to unleash the Pacific Bomber offensive that marked the "setting" of the rising sun. A convincing testament to the advances of the aircraft industry as a result of the Second World War.