Page 29 - Volume 10 Number 8

More bad news for Japan. A B-29 emerges from Plant II
in preparation for combat readiness checks. Laboring in two, 10-hour shifts, Boeing workers were completing 4.2 bombers per day in 1945. Of the 35,000 people dedicated to manufacturing the B-29, 40 percent were women.
By October 1945, Boeing had built 1,644 of the heavy bombers. (WICHITA STATE UNIVERSITY LIBRARIES, SPECIAL COLLECTIONS AND UNIVERSITY ARCHIVES)
proceed with the proposal and invited the Boeing Airplane Company, Douglas Aircraft Company and the Consolidated Aircraft Corporation to submit designs.
Of these three, Boeing’s Model 341 and Consolidated’s XB-32 were declared winners, but priority was given to the Model 341 with Consolidated’s design serving as a backup in case Boeing faltered. A key feature of the Model 341 was its wing design that combined the high-speed, low-drag, long-range characteristics of the Davis airfoil that already equipped Consolidated’s B-24 bomber. The Boeing wing would add large flaps along the trailing edge that would help generate lift for takeoff as well as provide optimum handling qualities at low approach and landing airspeeds. The disadvantage of the wing, however, was its high loading of 69 pounds per square foot of area.
In addition to the new wing, Boeing engineers planned to incorporate a modified version of the empennage installed on the B-17E. The long, slender and circular fuselage was designed to contain three pressurized compartments while the bomb bay, which could accommodate up to 10 tons of bombs, would remain unpressurized. The R-3350 static, air-cooled radial engines selected to power the B-29 were built by Wright Aeronautical Corporation and featured 18 cylinders capable of producing 2,200 horsepower. In 1939, the R-3350 was among the most sophisticated and powerful piston engines available in the United States, and derived its power from high compression ratios, higher RPM and supercharging that produced nearly one horsepower per pound of weight. By the end of 1939, Wright Aeronautical had built less than 100 of the engines and problems with cooling soon appeared and persisted for the next four years. The R-3350 radials installed on production bombers turned massive four-blade propellers built by Hamilton Standard.
By September 1940, the Air Corps had approved Boeing’s design and gave the company permission to proceed. One year later, as the war in Europe continued unabated, Boeing received an order for 250 bombers. That order was doubled six months later. The XB-29 first flew in September 1942 with veteran Boeing test pilot Eddie Allen at the controls. Although the new bomber flew well, the R-3350’s cooling problems continued,
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causing multiple engine failures early in the flight test program. A second prototype B-29 crashed into a factory building in December 1943 after an engine fire raged out of control. Eddie Allen, the entire flight crew and 19 people in the building, died.
General Arnold ordered a thorough investigation, which revealed that the intake and exhaust valves in certain cylinders were prone to overheating that caused the valve heads to separate from the valve stems. The debris was ingested into the engine and often caused a fire that, if not extinguished, spread to the magnesium alloy accessory section, which burned fiercely and weakened the main spar, burning through it in some cases. Meanwhile, the XB-29 and YB-29 prototypes continued to fly but were still beset with a long list of engine problems, including unsatisfactory cowl flap performance, rerouting of oil lines and tubes, redesign of intake and exhaust valves and many other issues too numerous to mention.
Meanwhile, Boeing was orchestrating a three-phase program for the B-29: Not only was the remaining XB-29 built without the benefit of detailed engineering drawings and parts, but the design, tooling and flight testing were all being conducted simultaneously! America’s entry into World War II was still six months away, but the rush was on to get the Superfortress into production. To make matters worse, the Air Corps demanded costly and time-consuming changes and revisions to changes that hampered progress. In addition, political pressures were mounting, beginning with the White House all the way down through Congress to General Arnold. As time passed and the B-29 was not yet ready for production, it was Arnold’s unwavering confidence in Boeing’s bomber that kept the program alive.
The evening of May 17, 1941, found Julius Earl Schaefer, general manager of Boeing-Wichita, talking on the telephone with a reporter. Schaefer was stunned to learn of a national effort to build $100 million-worth
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