Aviation Ancestry: August 2013

Swept-Wing Wonder, Part III

By Scott Schwartz

Retired B-47 on display at the March Field Air Museum. Notice how the aircraft seems poised to fly. The aircraft was designed with a built in eight-degree angle of attack, because the elevators could not produce enough force to rotate the aircraft for take off. (Scott Schwartz).Outfitting the Model 450 with tricycle landing gear would have necessitated the placement of bulges in the wings. This, of course, would have disrupted the smooth aerodynamics of the thin wings. Ironically, it was another demand placed on the design by the Air Force that led to a solution to the landing-gear problem. 

The Air Force wanted the new bomber to be able to carry an atomic bomb.  Since atomic bombs were very large, during the 1940s, aircraft carrying them needed very large bomb bays.  A bomb bay large enough to accommodate the atom bomb would not leave much room for landing gear to be mounted in the fuselage.  Well, luckily, the Air Force also came up with a solution to its problem – namely a “bicycle” landing gear arrangement.  In other words there would be two main landing gear trucks mounted in the fuselage, fore and aft.

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Aviation Ancestry - July 2013

Swept-Wing Wonder, Part II

By Scott Schwartz

The Boeing XB-47; note the “bicycle” landing gear arrangement. How the aircraft wound up with this landing gear set-up will be covered in the next Aviation Ancestry article in the August issue of In Flight USA. (Photo courtesy of the U.S. Air Force)Moving the engines to the top of the fuselage did little to resolve the drag problems, which in reality, were caused by the Model 432’s straight wings.  The high-speed potential of the jet engines simply could not be realized with the use of straight wings. 

Although the advantages of swept wings were known to many, these advantages were theoretical.  Theoretical, that is, until George Schairer’s letter reached Boeing. 

Why do swept wings allow greater flight speeds?  Because the air flowing over the top of a straight wing reaches supersonic speeds way before the rest of the aircraft; flying the aircraft faster will cause the air to separate from the top of the wing.  This separation – which is known as “drag-rise”– destroys lift and eventually leads to a stall.  On the other hand, the air flowing over a swept wing does so at a lower speed – therefore delaying drag-rise, and therefore providing lift at greater aircraft speeds. 

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Aviation Ancestry - June 2013

Swept-Wing Wonder:  The Boeing B-47

By Scott Schwartz

Jet aircraft during the piston era. Convair was one of three companies that responded to the Army’s request for a jet-bomber design. Looking pretty much like a piston-engine aircraft, Convair’s XB-46 is shown in flight, here. (Photo courtesy U.S. Air Force)World War II was at its peak during the summer of 1943.  The American aircraft industry was turning out piston-engine bombers, fighters, and other types by the thousands.  With production focused on these sorely-needed aircraft, it is an amazing truth that during this time, United States Army Air Forces planners were considering future production of a jet-propelled bomber.  Jet propulsion was certainly not “main stream;” the Bell XP-59 (a jet-powered fighter) was still being tested – and its performance was on a par with some piston-engine fighters of the time. In other words, jet-propulsion was in its infancy.

Still, some in the Army were far-sighted enough to see the jet engine’s potential, and the service distributed a request to several companies (Boeing among them) to investigate the idea of building a jet bomber around the new General Electric TG-180 jet engine.

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Aviation Ancestry - May 2013

The Other Wildcats

By Scott Schwartz

An Eastern Aircraft FM-2 in flight; note the shorter cowling. Most surviving Wildcats are General Motors-built FM-2s, which are powered by the nine-cylinder Wright Cyclone engine. (Scott Schwartz)Although it was intended to be a replacement for the F4F Wildcat, the “Zero-killer” F6F Hellcat was still being developed during the early part of 1942.  The company planned to stop the production of Wildcats altogether, once the Hellcat was ready for front-line service.  Because the transition on the assembly line from one aircraft to another would not be instantaneous, Grumman had to find a way to maintain a steady stream of combat aircraft coming off the line, while Hellcat production gained momentum.

The answer was to have another company build F4F Wildcats and TBF Avengers

In the meantime General Motors had stopped making passenger cars shortly after the U.S. entered the war. This left several G.M. plants with nothing to produce. 

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Aviation Ancestry - April 2013

From “Gusto” To “Oxcart” Pt. VI

By Scott Schwartz

Thirsty SR-71 meets a KC-135Q. (Courtesy of the United States Air Force)With General LeMay’s promise to buy Blackbird interceptors and reconnaissance aircraft, things looked bright for the Skunk Works.  Even more tantalizing was the fact that an Air Force colonel let it slip to Johnson that LeMay had thought further about the matter, and that the General and his staff were now working on a proposal for the construction of twenty Blackbirds per month.  Specifically, General LeMay wanted Lockheed to build ten Blackbird interceptors and ten Blackbird bombers each month.

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