In traditional aircraft design, the center of gravity of the aircraft is always located in front of the lift center of the wing. This causes the lift provided by the wing to break the balance of the fuselage, and the aircraft can easily cause the nose of the aircraft to dive downward. In order to balance this trend, some control wings with small downward force are usually designed on the tail of the aircraft to offset the dive tendency of the aircraft. The basic principle is that the aircraft can fly freely within certain angles. When the power is reduced, the speed decreases, the lift of the wings decreases, the nose of the aircraft will naturally lower, and then the aircraft will begin to descend.
There are many obstacles to making airplanes simple and safe. The control surface located on the tail of the aircraft often makes the aircraft longer than the actual required length. Most of these extended fuselages cannot bear the load due to balance considerations. In addition, the existence of the control surface will also increase drag and reduce the aircraft's performance. overall performance. The biggest problem is that these wings increase drag and also increase the weight of the aircraft, which requires the aircraft engine to provide additional thrust to generate more lift than the original aircraft requires.
The traditional layout of the aircraft - the load is in the front and the control surface is in the back - also causes another problem, that is, it causes a backward bending tendency (deflection) of the wing, so sometimes the wing Either in front of or behind the center of gravity, and aircraft stability and control (through the extra wing) are equally important. However, drag and weight can be reduced without additional control surfaces, which in most cases can significantly reduce flight drag and allow designers to concentrate on stability issues.
The only disadvantage of flying wings is that in order to better hide the fuselage in the wings, the wings of the aircraft must be designed to be much thicker than normal wings. This doesn't matter at low speeds, but when the aircraft approaches the speed of sound, a huge drag effect occurs in the relatively thick parts of the wing, so flying wings are not suitable for high-speed aircraft, which are more sensitive to drag than ordinary aircraft. In addition, a series of stability problems will occur at high speeds, such as "Mach dive", and designers need to go through a lot of hard work to solve them.
For these reasons, research on flying wings was limited to the 1930s and 1940s, when flying wings were considered a natural solution for producing large passenger aircraft that could carry a large number of passengers. It can also carry enough fuel for scheduled transatlantic flights. The huge internal volume and low drag of the flying wing make it naturally play this role. Jack Northrop of the United States, Alexander Liebig and the Schott brothers of Germany have all conducted research in this area, and Hugo of Germany ·Junkers had patented a flying-wing glider concept in 1910.
Junkers began his great JG1 design in 1919 by trying to put passengers inside the thick wings. But in 1921, the Joint Air Control Board announced that the unfinished JG1 aircraft broke the post-World War I restrictions on the size of German aircraft. Juncker envisioned a futuristic flying wing that could accommodate up to 1,000 passengers. The closest thing to a successful reality was the 1931 The Junkers G-38 34-seat Grossflugzeug aircraft, with the passenger cabin located at the leading edge of the wing and embedded inward into the wing, was the largest land aircraft (relative to seaplanes) at the time. The G-38, nicknamed the "Flying Hotel", joined the Lufthansa fleet. , it was later converted to military use until it was destroyed by British forces retreating from Athens in 1941. Japan obtained Juncker's authorization to build several G-38s as bombers.
Many German military aircraft designed in the late World War II were based on flying wings or were modified to maximize the range of jet-engined aircraft. The most famous is the Gotha Go-229. This aircraft first flew in 1944. It not only combined the concept of flying wings (Nürflugel), but also had two jet engines hidden in the composite wings that could absorb radar waves. The prototype of the aircraft is still preserved in its original condition by the Smithsonian. In 2008, a model produced by Northrop Grumman shows that when the British radar system detected the Ho 299 fighter, only two and a half minutes were left in the interception. Time means that Britain at that time was unable to defend itself.
Many post-war conceptual designs were based on the plane shape of the aircraft, but problems soon emerged.
In order to extend the bomber's range, interest in flying wings continued into the 1950s. The Northrop B-49 bomber was its last swan song, but it was not put into production. Even the flying wing design could not make up for the fuel load requirements. , later larger conventional aircraft like the Boeing B-52 bomber were built to replace the flying wing design. Subsequent long-range bombers never again adopted the form of flying wings until the emergence of the B-2 Phantom stealth strategic bomber.
In the 1980s, flying wings once again attracted attention as a way to significantly reduce radar reflection signals, which eventually led to the advent of Northrop's B-2 Phantom stealth strategic bomber. Excellent aerodynamics was not a critical issue in this project.
Because the flying wing can still maintain excellent performance in the medium and low speed range, its vision as a tactical transport aircraft has never been interrupted. Boeing has been conducting research on a project using a wing-body fused transport aircraft. The transport aircraft is the size of the Lockheed C-130 Hercules transport aircraft, but has a longer range and 1/3 more payload. Many companies such as Boeing, McDonnell Douglas, and De Havilland have considered designing flying-wing passenger aircraft, but so far they have not been realized; problems that will arise when using this design for passenger aircraft include comfort (except for the center when turning) Outside the seats, there will be excessive inclination), too few windows, greater difficulty in escape, and the airport design needs to be changed.