Aviation Ancestry - January 2012
The B-29 Superfortress
By Scott Schwartz
The Boeing XB-29: notice the early three-bladed propellers and the lack of gun turrets. The Army experimented with various defensive armament during the early phases of the B-29 program. (Photo courtesy of the United States Air Force) )The B-29 Superfortress’s engines had a tendency to overheat and catch fire. Its defensive gun system sometimes jammed or simply failed altogether. Yet, in many respects, this aircraft changed the world after it was used on two very special missions during World War II.
During the early 1930s, U.S. Army planners had been thinking about (perhaps dreaming would be a more accurate word) a new bomber that could carry 2,000 pounds of bombs, and which had a range of more than 5,000 miles. By 1940 though, these imaginings had coalesced into a concrete set of specifications. The new bomber would have to carry 2,000 pounds of bombs and be able to fly more than 5,300 miles. Oh, and it would also have to be able to fly faster than 400 mph. The reader should remember that in 1940, the fastest fighters in first-line service could not achieve 400 mph in level flight!
This was indeed a tall order. Nevertheless, four manufacturers submitted proposals.
Lockheed’s proposal looked liked an armed Constellation, which is essentially what it was. This aircraft, the XB-30, never got beyond the design stage. Neither did the Douglas design, which was known as the XB-31.
On the other hand, the Consolidated design did actually make it into production as the B-32 Dominator, but only as a backup in case the primary program failed.
The company that wound up producing the “primary program” bomber, Boeing, had an advantage over the other companies in that it had been working on long-range aircraft concepts since the early 1930s. These ideas eventually took the form of the Model 334, which used a wing that was similar to that of the Boeing Clipper flying boat, as well as a twin-vertical tail. This aircraft would have utilized four Wright horizontally-opposed, liquid-cooled engines. These engines would have been buried within the wings, allowing them to be built with a thin cross-section. Well, these particular “flat” engines never came to pass, and the design was revised to incorporate four Pratt & Whitney R-2800 engines, a circular, glass-nosed fuselage, and a wing that was similar to that of the B-24. This was the model 334A.
Refining the design even further, Boeing “made” (the reader should remember that this was all on paper, at this point) the fuselage even more streamlined and replaced the twin tail with a single vertical stabilizer. Now known as the Model 341, this design was submitted to the U.S. Army Air Corps, which, based on combat experience being reported by the Royal Air Force, was found wanting. Two big items were needed: much heavier defensive firepower and self-sealing fuel tanks. Of course, these things would add weight. Since the new bomber was supposed to be a long-range aircraft, more fuel would have to be carried. Because it was too small to meet these new requirements, the Model 341 was shelved in favor of the larger Model 345, the existence of which was revealed on May 11, 1940. In addition to being larger, the Model 345 was to be powered by the new Wright R-3350, eighteen cylinder engines.
Because it was supposed to be a major improvement over its “cousin,” the B-17, Boeing called its new bomber “Superfortress.”
The Army was impressed enough to order two prototypes, under the designation “XB-29” during the summer of 1940. Another prototype was ordered in December of that same year.
By the spring of 1941, a full-scale wooden mock-up had been inspected and approved by the Army, and in May, the Army ordered 14 YB-29’s for in-service testing. It also ordered 250 production aircraft – B-29’s. Several weeks after the Japanese attacked Pearl Harbor, the production order was doubled. All of these orders were placed before a single prototype had been produced!
Now officially referred to as the Superfortress, the first XB-29 was ready for testing on Sept. 21, 1942.
Technologically speaking, the XB-29 was on the cutting edge. It was the first bomber with a pressurized interior (except for the bomb-bay), and it was the first aircraft to be powered by the new Wright R-3350 engines, each of which could generate 2,200 horsepower. The astute reader may notice that the famous General-Electric centralized fire-control gun system has not been mentioned in connection with the XB-29. The truth is that several different defensive armament arrangements were tested on the XB-29-including manned turrets. Ultimately, the Army chose to equip the XB-29 with four Sperry remotely-operated turrets. Two of the turrets were installed in the top of the fuselage, and two in the bottom. The guns were aimed through periscopes that were mounted behind Plexiglas “blisters” on the aft-end of the fuselage. There was also a manned tail-gunner’s position, with provision for two .50 caliber machines and a lone 20 mm cannon.
A Wright R-3350, twin-row, eighteen cylinder engine. The version used on the B-29 could generate 2,200 horsepower. Unfortunately, engine fires plagued the B-29 throughout its service life. (Photo courtesy of the United States Air Force)The new Wright engines, coupled with the XB-29’s aerodynamically clean design, were expected to give the XB-29 a top speed of 368 mph and a service ceiling of 32,100 feet. After the XB-29’s first flight, which occurred on Sept. 21, 1942, Boeing test pilot Edmund “Eddie” Allen stated simply that “she flies.” All went well on this flight, which lasted 45 minutes. Indeed, the aircraft performed well during most of the early flights. However, serious problems – in the form of engine fires – soon cropped up.
To be continued…….
