Items of war
The Boeing Company in Seattle produced the "Strategic Spear" for the Allies in World War II— the B-17 and B-29 heavy bombers, and the massive fleet of Boeing bombers dominated the skies of Berlin and Tokyo. The protagonist of this article begins during World War II, but not the shining silver iron birds of the war, but the black technology jets that were still highly classified at the time.
Like Germany, U.S. military jet combat aircraft development dates back to World War II, and in 1943 the U.S. Army Air Force (USAAF) issued requirements for new jet-bomber/reconnaissance aircraft to suppliers and in 1944 as a formal demand project. The supplier was asked to provide an aircraft that surpassed any of its 1944 counterpart bombers.
Indicators include: speeds of 805 kph (500 mph) or higher, ranges of 5,635 km (3,500 mi), and a ceiling of 12,200 m (40,000 ft). The bombers will be powered by General Electric's TG-180 turbojet engines. During the development phase. Boeing, Cornwall and North American companies responded.
Model 424
Model 413
This was Boeing's first exposure to jet power, Boeing's first proposal was that the "Model 413" was similar to its opponent, the cigar-type fuselage resembled a shrunken B-29 super air fortress, the two engine compartments under the slightly thin flat wings were each equipped with two TG-180 turbojet engines, and then Boeing added a sleek (fighter-style) cockpit, and the scheme was changed to the Model 424. The National Advisory Committee on Aeronautics (NACA, the predecessor of NASA) conducted wind tunnel tests on the Model 424 model, and experiments showed that the design had excessive drag problems.
Model 413
Model 432
Boeing engineers proposed a revised design in April 1944, the "Model 432", which retained straight wings but buried four engines in the forward-facing fuselage, with air intakes on both sides and discharged from the rear vents. However, despite the structural advantages of the Model 432, changing the engine layout did not significantly reduce excessive resistance.
The 432's back spout
This lens gives a good angle to look at the side air intakes of the 432, which shows that the 432 is still the first three-point landing gear design.
Model 448
This "open mouth" nose is characteristic of the Model 448
By then, the war in Europe was clearly nearing its end. General "Hap" Arnold, head of the USAAF, asked von Karman," a prominent aerodynamicist at the California Institute of Technology (Dr. Qian's mentor), to set up a "Scientific Advisory Group" (SAG) to travel to postwar Europe to assess U.S. military capture of German aviation technology.
Boeing's study of the shape of high-speed wings
Another member of the SAG is George Schairer, Boeing's chief aerodynamicist. While in Germany, he studied experimental data on swept wings obtained by German aircraft manufacturers and found that the Germans' understanding of the technology was already ahead of their allies. In May 1945, Scheler wrote a memorandum for Boeing management proposing a comprehensive study of the swept wing.
Model 448
Model 448
Boeing engineers then turned to studying the swept wing data obtained from the Germans, and a study conducted by Boeing aerodynamicist Vic Ganzer showed that the optimal swept angle was 35 degrees.
Model 448, tested No. 5 and No. 6 engines in the wingtip
Model 448 wind tunnel model, tested No. 5 and 6 engines in the flat tail tip
The option to upgrade with swept wings is the "Model 448". In addition to the swept wings, the 448 also added two engines. Project manager George Martin felt that four engines were still underpowered and decided to add two more engines to improve performance. However, the fuselage of the 448 has not allowed the addition of more engines, through the wind tunnel experiment test including wingtip, flat tail tip and many other installation positions, and finally decided to add two additional TG-180 in the tail, other improvements also include the fuselage engine on both sides of the air intake to the nose intake, the narrow intake of the four engines to divide the cockpit into two parts, which forms the final layout of the 448 scheme.
448 wind tunnel model
At the same time, USAAF reintegrated the jet bomber program, adding Martin to the bidders, hence the product of the four bidders, known as the "Type 45 Bomber." The engineers of the year did not have much experience with the configuration of the jet bomber, and USAAF was very rich and made a domineering "I want it all" decision, and all four bidders won the prototype contract.
Model 450
Model 450
Now, it's hard to imagine an aircraft with a layout like the 448 being successful, because the engine nozzle located on the back of the fuselage is a big problem, and the engineers of the year seriously underestimated the power of the jet engine wake, and it was difficult not to fall apart in the tail and even the rear fuselage. BASED ON THE SAME CONCERN USAAF ALSO DISLIKES 448 AND IMMEDIATELY REJECTED IT.
Model 450
USAAF required the engine to have to be moved back to the wing, which went straight back to the drag problem, but the engineering team came up with a clean, elegant solution that ultimately placed the engine in a streamlined pod under the wing. Boeing's engineers did not realize that the pod layout they came up with under the pressure of USAAF was an absolute perfect solution, and boeing has since adopted a pod layout for almost all large aircraft. The pod layout not only solves the drag problem, but also makes it very easy to maintain the engine, and it is easy to upgrade the new engine without worrying too much about the volume problem.
After another upgrade to the "Model 450", each wing wing heel was equipped with a two-TG-180 pod, the other TG-180 was initially located at the wingtip and then adjusted to the pod in front of the wingtip.
The Air Force approved the 450, so the Boeing team continued to refine it. One problem is the landing gear. There is no room for landing gear on thin wings, and placing the landing gear of a tricycle on the fuselage destroys the structure of the aircraft and degrades its performance, especially taking up valuable bomb bay space, the solution is the "bicycle" landing gear.
Win
B-47
USAAF was so pleased with the exquisite 450 that in April 1946 two prototypes were ordered, giving the official designation "XB-47". On December 17, 1947, the XB-47 made its maiden flight, killed two opponents in the comparative test flight, removed the X, and became the B-47 stratospheric jet bomber, and Boeing's jet age officially began.
Designer and model of three programs of the XB-47 project
B-47 evolution
Looking back now, Boeing invested more technological innovation than its three rivals and happened to have chosen an unparalleledly excellent layout.
Boeing's advertising at that time was bragging about the wings